From 10cb2f0f5033723f7b7fc965b19395e0322e57f1 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 15:25:01 +0100
Subject: [PATCH 01/21] Remove duplication

---
 rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh | 139 +------------------
 1 file changed, 1 insertion(+), 138 deletions(-)
 mode change 100755 => 120000 rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh

diff --git a/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh b/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh
deleted file mode 100755
index a228dca..0000000
--- a/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh
+++ /dev/null
@@ -1,138 +0,0 @@
-#!/bin/bash
-#
-# Copyright (C) 2020-2025 BlueRock Security, Inc.
-#
-# This software is distributed under the terms of the BedRock Open-Source License.
-# See the LICENSE-BedRock file in the repository root for details.
-#
-
-usage() {
-	cat >&2 <<-EOF
-		usage: $(basename "$0") [ -t ] <filename>.<ext> <cpp2v-options> -- [ <clang-options> ]
-
-		This will output (to stdout) dune rules for building <filename>.<ext>,
-		passing <options> to cpp2v. Redirect output to dune.inc and
-		load via dune's include.
-
-		The output is filesystem-independent and <filename>.<ext> need not exist.
-		Placing the output in <base>/dune.inc will transform
-		<base>/<filename>.<ext> into <base>/<filename>_<ext>.v and
-		<base>/<filename>_<ext>_names.v and (with \`-t\`)
-		<base>/<filename>_<ext>_templates.v.
-	EOF
-	exit 1
-}
-
-outRule() {
-	local indent fullName name ext
-	indent="$1"
-	fullName="$2"
-	shift 2
-
-	# The extension starts at the last dot:
-	name="${fullName%.*}"
-	if [ "$name" = "$fullName" ]; then
-		echo -e "Error: filename '$fullName' has no extension\n" >&2
-		usage
-	fi
-	ext="${fullName##*.}"
-
-	local module="${name}_${ext}.v"
-	local targ="${module}"
-	local clang_options=""
-	local universe=""
-	if [ "$system" = 1 ]; then
-		universe=" (universe)"
-	fi
-	local cpp2v="cpp2v -v %{input} -o ${module}"
-
-	if [ "$gen_names" = 1 ]; then
-		local names="${name}_${ext}_names.v"
-		targ="${targ} ${names}"
-		cpp2v="${cpp2v} -names ${names}"
-	fi
-
-	if [ "$templates" = 1 ]; then
-		local templates="${name}_${ext}_templates.v"
-		cpp2v="${cpp2v} --templates=${templates}"
-		targ="$targ ${templates}"
-	fi
-
-	action="(run ${cpp2v} ${1+ $@} ${clang_options})"
-
-	sed "s/^/${indent}/" <<-EOF
-		(rule
-		 (targets ${module}.stderr ${targ})
-		 (alias test_ast)
-		 (deps (:input ${name}.${ext}) (glob_files_rec ${prefix}*.hpp)${universe})
-		 (action
-		 	 (with-stderr-to ${module}.stderr ${action})))
-		(alias (name srcs) (deps ${name}.${ext}))
-	EOF
-	# TODO: maybe drop @srcs alias, seems leftover from !2613
-}
-
-traverse() {
-	local indent path firstDir rest
-	indent="$1"
-	path="$2"
-	shift 2
-	firstDir="${path%%/*}"
-	rest="${path#*/}"
-	if [ "$firstDir" = "$path" ]; then
-		outRule "$indent" "$path" "$@"
-	elif [ "$firstDir" = "." ]; then
-		traverse "$indent" "$rest" "$@"
-	else
-		#echo DIR $firstDir
-		#echo REST $rest
-		echo "${indent}(subdir ${firstDir}"
-		(cd "${firstDir}"; traverse " $indent" "$rest" "$@")
-		echo "${indent})"
-	fi
-}
-
-gen_names=0
-templates=0
-system=0
-prefix="../"
-while :
-do
-	case "$1" in
-	-n)
-		gen_names=1
-		shift
-		;;
-	-t)
-		templates=1
-		shift
-		;;
-	-s)
-		system=1
-		shift
-		;;
-	-p)
-		shift
-		prefix="$1"
-		shift
-		;;
-	--)
-		shift
-		break
-		;;
-	-*)
-		usage
-		;;
-	*)
-		break
-		;;
-	esac
-done
-[ $# -ge 1 ] || usage
-
-path="$1"
-shift
-
-traverse "" "$path" "$@"
-
-# vim:set noet sw=8:
diff --git a/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh b/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh
new file mode 120000
index 0000000..de18be0
--- /dev/null
+++ b/rocq-brick-libstdcpp/proof/cpp2v-dune-gen.sh
@@ -0,0 +1 @@
+../test/cpp2v-dune-gen.sh
\ No newline at end of file

From 6cec5c28e916846b7bc1bd9af14dea779aadfe74 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 15:25:54 +0100
Subject: [PATCH 02/21] Add --no-elaborate

---
 rocq-brick-libstdcpp/test/cpp2v-dune-gen.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rocq-brick-libstdcpp/test/cpp2v-dune-gen.sh b/rocq-brick-libstdcpp/test/cpp2v-dune-gen.sh
index a228dca..d6ef98b 100755
--- a/rocq-brick-libstdcpp/test/cpp2v-dune-gen.sh
+++ b/rocq-brick-libstdcpp/test/cpp2v-dune-gen.sh
@@ -44,7 +44,7 @@ outRule() {
 	if [ "$system" = 1 ]; then
 		universe=" (universe)"
 	fi
-	local cpp2v="cpp2v -v %{input} -o ${module}"
+	local cpp2v="cpp2v -v %{input} -o ${module} --no-elaborate"
 
 	if [ "$gen_names" = 1 ]; then
 		local names="${name}_${ext}_names.v"

From cfb0af5696a2e527df5572daf9560bd8d8e52c41 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 15:25:22 +0100
Subject: [PATCH 03/21] TMP Update generated dune.inc

---
 rocq-brick-libstdcpp/proof/dune.inc | 36 ++++++++++++++---------------
 rocq-brick-libstdcpp/test/dune.inc  | 21 ++++++++++++-----
 2 files changed, 33 insertions(+), 24 deletions(-)

diff --git a/rocq-brick-libstdcpp/proof/dune.inc b/rocq-brick-libstdcpp/proof/dune.inc
index dd49356..4482e93 100644
--- a/rocq-brick-libstdcpp/proof/dune.inc
+++ b/rocq-brick-libstdcpp/proof/dune.inc
@@ -1,82 +1,82 @@
 ; DO NOT EDIT: Generated by "./dune-gen.sh"
 (subdir cassert
  (rule
-  (targets inc_cassert_cpp.v.stderr inc_cassert_cpp.v)
+  (targets inc_cassert_cpp.v)
   (alias test_ast)
   (deps (:input inc_cassert.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_cassert_cpp.v.stderr (run cpp2v -v %{input} -o inc_cassert_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_cassert_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc_cassert.cpp))
 )
 (subdir cctype
  (rule
-  (targets inc_cctype_cpp.v.stderr inc_cctype_cpp.v)
+  (targets inc_cctype_cpp.v)
   (alias test_ast)
   (deps (:input inc_cctype.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_cctype_cpp.v.stderr (run cpp2v -v %{input} -o inc_cctype_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_cctype_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc_cctype.cpp))
 )
 (subdir cstdlib
  (rule
-  (targets inc_cstdlib_cpp.v.stderr inc_cstdlib_cpp.v)
+  (targets inc_cstdlib_cpp.v)
   (alias test_ast)
   (deps (:input inc_cstdlib.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_cstdlib_cpp.v.stderr (run cpp2v -v %{input} -o inc_cstdlib_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_cstdlib_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc_cstdlib.cpp))
 )
 (subdir mutex
  (rule
-  (targets demo_cpp.v.stderr demo_cpp.v)
+  (targets demo_cpp.v)
   (alias test_ast)
   (deps (:input demo.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to demo_cpp.v.stderr (run cpp2v -v %{input} -o demo_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps demo.cpp))
 )
 (subdir mutex
  (rule
-  (targets inc_hpp.v.stderr inc_hpp.v)
+  (targets inc_hpp.v)
   (alias test_ast)
   (deps (:input inc.hpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_hpp.v.stderr (run cpp2v -v %{input} -o inc_hpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc.hpp))
 )
 (subdir mutex
  (rule
-  (targets test_cpp.v.stderr test_cpp.v)
+  (targets test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps test.cpp))
 )
 (subdir new
  (rule
-  (targets inc_new_cpp.v.stderr inc_new_cpp.v)
+  (targets inc_new_cpp.v)
   (alias test_ast)
   (deps (:input inc_new.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_new_cpp.v.stderr (run cpp2v -v %{input} -o inc_new_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_new_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc_new.cpp))
 )
 (subdir semaphore
  (rule
-  (targets inc_hpp.v.stderr inc_hpp.v)
+  (targets inc_hpp.v)
   (alias test_ast)
   (deps (:input inc.hpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to inc_hpp.v.stderr (run cpp2v -v %{input} -o inc_hpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps inc.hpp))
 )
 (subdir semaphore
  (rule
-  (targets test_cpp.v.stderr test_cpp.v)
+  (targets test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps test.cpp))
 )
diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index 37569d2..a781725 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -1,28 +1,37 @@
 ; DO NOT EDIT: Generated by "./dune-gen.sh"
 (subdir cctype
  (rule
-  (targets test_cpp.v.stderr test_cpp.v)
+  (targets test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps test.cpp))
 )
 (subdir cstdlib
  (rule
-  (targets test_cpp.v.stderr test_cpp.v)
+  (targets test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps test.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N0_hello_world_cpp.v)
+  (alias test_ast)
+  (deps (:input N0_hello_world.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N0_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N0_hello_world.cpp))
+)
 (subdir new
  (rule
-  (targets demo_cpp.v.stderr demo_cpp.v)
+  (targets demo_cpp.v)
   (alias test_ast)
   (deps (:input demo.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-  	 (with-stderr-to demo_cpp.v.stderr (run cpp2v -v %{input} -o demo_cpp.v  -- -std=c++20 -stdlib=libstdc++ ))))
+                         (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps demo.cpp))
 )

From b6ef46fe39828829e72d374cb1e5eaea1c531740 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 15:35:36 +0100
Subject: [PATCH 04/21] Examples WIP

---
 .../N0_hello_world.cpp                        | 22 +++++
 .../geeks_for_geeks_examples/N0_hello_world.v | 85 +++++++++++++++++++
 2 files changed, 107 insertions(+)
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
new file mode 100644
index 0000000..e570d51
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
@@ -0,0 +1,22 @@
+#include <iostream>
+// #include <bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+  // Printing the name using cout object
+  cout << "Anmol";
+  return 0;
+}
+
+// #include <iostream>
+// #include <stdio.h>
+
+// using namespace std;
+
+// int main() {
+//   // Printing the name
+//   puts("Anmol");
+//   cout << "Anmol";
+//   return 0;
+// }
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
new file mode 100644
index 0000000..a830cd8
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
@@ -0,0 +1,85 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.cpp.string.
+Require Import skylabs.lang.cpp.parser.plugin.cpp2v.
+
+(** TODO upstream *)
+#[only(cfracsplittable)] derive cstring.R.
+
+(** TODO upstream *)
+Bind Scope bs_scope with cstring.t.
+(* We only have `Bind Scope bs_scope with t.` inside `Module cstring.` *)
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N0_hello_world_cpp.
+
+(* cpp.prog source prog cpp:{{
+
+// #include <iostream>
+#include <stdio.h>
+
+int main() {
+  // Printing the name
+  puts("Anmol");
+  // cout << "Anmol";
+  return 0;
+}
+}}. *)
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  Parameter ostreamT : Type.
+  Parameter ostreamR : cQp.t -> ostreamT -> Rep.
+  Parameter ostream_contentR : cQp.t -> cstring.t -> Rep.
+  Instance: LearnEqF1 ostreamR := ltac:(solve_learnable).
+  Instance: LearnEqF1 ostream_contentR := ltac:(solve_learnable).
+
+  cpp.spec "std::operator<<<std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&, const char*)" from source as ostream_insert_spec with (
+    \arg{osP} "" (Vptr osP)
+    \prepost{osM} osP |-> ostreamR 1$m osM
+    \pre{str} osP |-> ostream_contentR 1$m str
+    \arg{strP} "" (Vptr strP)
+    \prepost{q__s strM} strP |-> cstring.R q__s strM
+    \post[Vptr osP]
+      osP |-> ostream_contentR 1$m (str ++ strM)).
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m (str ++ "Anmol")).
+
+  (* cpp.spec "puts" from source as puts_spec with (
+    \arg{p} "" (Vptr p)
+    \prepost{q s} p |-> cstring.R q s
+    \post{n}[Vint n] emp). *)
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_spec; go.
+  Qed.
+
+End with_cpp.
+
+(* #include <bits/stdc++.h> *)
+
+(* cpp.prog source prog cpp:{{
+
+#include <iostream>
+
+using namespace std;
+
+int main() {
+  // Printing the name using cout object
+  cout << "Anmol";
+  return 0;
+}
+}}.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  cpp.spec "main()" as main_spec with
+    (\post emp).
+
+
+End with_cpp. *)

From 24cb3217b0f8109631cb30544af4c8118d593fae Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 16:34:41 +0100
Subject: [PATCH 05/21] Cleanup first example a bit

---
 rocq-brick-libstdcpp/test/dune.inc            |  9 +++
 .../N0_hello_world.cpp                        | 16 +----
 .../geeks_for_geeks_examples/N0_hello_world.v | 66 +------------------
 .../geeks_for_geeks_examples/iostream.cpp     |  1 +
 .../test/geeks_for_geeks_examples/spec.v      | 32 +++++++++
 5 files changed, 48 insertions(+), 76 deletions(-)
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/iostream.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v

diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index a781725..ac9c705 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -26,6 +26,15 @@
                          (run cpp2v -v %{input} -o N0_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps N0_hello_world.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets iostream_cpp.v)
+  (alias test_ast)
+  (deps (:input iostream.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o iostream_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps iostream.cpp))
+)
 (subdir new
  (rule
   (targets demo_cpp.v)
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
index e570d51..eef6f4f 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
@@ -1,3 +1,4 @@
+// https://www.geeksforgeeks.org/cpp/writing-first-c-program-hello-world-example/
 #include <iostream>
 // #include <bits/stdc++.h>
 
@@ -5,18 +6,7 @@ using namespace std;
 
 int main() {
   // Printing the name using cout object
-  cout << "Anmol";
+  cout << "Hello World";
+
   return 0;
 }
-
-// #include <iostream>
-// #include <stdio.h>
-
-// using namespace std;
-
-// int main() {
-//   // Printing the name
-//   puts("Anmol");
-//   cout << "Anmol";
-//   return 0;
-// }
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
index a830cd8..21fd44d 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
@@ -1,52 +1,16 @@
 Require Import skylabs.auto.cpp.prelude.proof.
-Require Import skylabs.cpp.string.
-Require Import skylabs.lang.cpp.parser.plugin.cpp2v.
-
-(** TODO upstream *)
-#[only(cfracsplittable)] derive cstring.R.
-
-(** TODO upstream *)
-Bind Scope bs_scope with cstring.t.
-(* We only have `Bind Scope bs_scope with t.` inside `Module cstring.` *)
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N0_hello_world_cpp.
 
-(* cpp.prog source prog cpp:{{
-
-// #include <iostream>
-#include <stdio.h>
-
-int main() {
-  // Printing the name
-  puts("Anmol");
-  // cout << "Anmol";
-  return 0;
-}
-}}. *)
-
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
-  Parameter ostreamT : Type.
-  Parameter ostreamR : cQp.t -> ostreamT -> Rep.
-  Parameter ostream_contentR : cQp.t -> cstring.t -> Rep.
-  Instance: LearnEqF1 ostreamR := ltac:(solve_learnable).
-  Instance: LearnEqF1 ostream_contentR := ltac:(solve_learnable).
-
-  cpp.spec "std::operator<<<std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&, const char*)" from source as ostream_insert_spec with (
-    \arg{osP} "" (Vptr osP)
-    \prepost{osM} osP |-> ostreamR 1$m osM
-    \pre{str} osP |-> ostream_contentR 1$m str
-    \arg{strP} "" (Vptr strP)
-    \prepost{q__s strM} strP |-> cstring.R q__s strM
-    \post[Vptr osP]
-      osP |-> ostream_contentR 1$m (str ++ strM)).
-
-  cpp.spec "main()" from source as main_spec with (
+  cpp.spec "main()" from N0_hello_world_cpp.source as main_spec with (
     \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
     \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
     \post[Vint 0]
-      _global "std::cout" |-> ostream_contentR 1$m (str ++ "Anmol")).
+      _global "std::cout" |-> ostream_contentR 1$m (str ++ "Hello World")).
 
   (* cpp.spec "puts" from source as puts_spec with (
     \arg{p} "" (Vptr p)
@@ -59,27 +23,3 @@ Section with_cpp.
   Qed.
 
 End with_cpp.
-
-(* #include <bits/stdc++.h> *)
-
-(* cpp.prog source prog cpp:{{
-
-#include <iostream>
-
-using namespace std;
-
-int main() {
-  // Printing the name using cout object
-  cout << "Anmol";
-  return 0;
-}
-}}.
-
-Section with_cpp.
-  Context `{Σ : cpp_logic, σ : genv}.
-
-  cpp.spec "main()" as main_spec with
-    (\post emp).
-
-
-End with_cpp. *)
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/iostream.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/iostream.cpp
new file mode 100644
index 0000000..604782e
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/iostream.cpp
@@ -0,0 +1 @@
+#include <iostream>
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
new file mode 100644
index 0000000..9321767
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -0,0 +1,32 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Export skylabs.cpp.string.
+
+(** TODO upstream *)
+#[only(cfracsplittable)] derive cstring.R.
+
+(** TODO upstream *)
+#[global] Bind Scope bs_scope with cstring.t.
+(* We only have `Bind Scope bs_scope with t.` inside `Module cstring.` *)
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.iostream_cpp.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  Parameter ostreamT : Type.
+  Parameter ostreamR : cQp.t -> ostreamT -> Rep.
+  Parameter ostream_contentR : cQp.t -> cstring.t -> Rep.
+
+  #[global] Instance: LearnEqF1 ostreamR := ltac:(solve_learnable).
+  #[global] Instance: LearnEqF1 ostream_contentR := ltac:(solve_learnable).
+
+  cpp.spec "std::operator<<<std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&, const char*)" from source as ostream_insert_spec with (
+    \arg{osP} "" (Vptr osP)
+    \prepost{osM} osP |-> ostreamR 1$m osM
+    \pre{str} osP |-> ostream_contentR 1$m str
+    \arg{strP} "" (Vptr strP)
+    \prepost{q__s strM} strP |-> cstring.R q__s strM
+    \post[Vptr osP]
+      osP |-> ostream_contentR 1$m (str ++ strM)).
+
+End with_cpp.

From 7e4d58985bc4fd05ba000cd9b662a7af44abd02c Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 16:34:59 +0100
Subject: [PATCH 06/21] New example, stuck on bug? Changing next

---
 rocq-brick-libstdcpp/test/dune.inc            |  9 +++
 .../geeks_for_geeks_examples/N2_input.cpp     | 24 +++++++
 .../test/geeks_for_geeks_examples/N2_input.v  | 65 +++++++++++++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v

diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index ac9c705..a5b255d 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -26,6 +26,15 @@
                          (run cpp2v -v %{input} -o N0_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps N0_hello_world.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N2_input_cpp.v)
+  (alias test_ast)
+  (deps (:input N2_input.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N2_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N2_input.cpp))
+)
 (subdir geeks_for_geeks_examples
  (rule
   (targets iostream_cpp.v)
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
new file mode 100644
index 0000000..1da1f13
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
@@ -0,0 +1,24 @@
+// https://www.geeksforgeeks.org/cpp/input-in-cpp/
+
+#include <iostream>
+using namespace std;
+
+// int main(){
+//     int i;
+//     // Take input using cin
+//     cin >> i;
+//     // Print output
+//     cout << i;
+//     return 0;
+// }
+
+int main() {
+    string name;
+    int age;
+    // Take multiple input using cin
+    cin >> name >> age;
+    // Print output
+    cout << "Name : " << name << endl;
+    cout << "Age : " << age << endl;
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
new file mode 100644
index 0000000..b3de793
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
@@ -0,0 +1,65 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N2_input_cpp.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  Parameter istreamT : Type.
+  Parameter istreamR : cQp.t -> istreamT -> Rep.
+  (* Parameter istream_contentR : cQp.t -> cstring.t -> Rep. *)
+
+  cpp.spec "main()" from N2_input_cpp.source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m (str ++ "Hello World")).
+
+  (* cpp.spec "puts" from source as puts_spec with (
+    \arg{p} "" (Vptr p)
+    \prepost{q s} p |-> cstring.R q s
+    \post{n}[Vint n] emp). *)
+
+  Parameter cppStringR : cQp.t -> cstring.t -> Rep.
+  cpp.spec "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::basic_string()" from source as string_ctor_spec with (
+    \this this
+    \post this |-> cppStringR 1$m "").
+
+  #[global] Declare Instance cppStringR_typed : Typed2 "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>" cppStringR.
+
+  #[ignore_missing]
+  cpp.spec
+  "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"
+  from source as istream_take_char_spec with (
+  (* cpp.spec "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)" from source with ( *)
+    \arg{isP} "" (Vptr isP)
+    \pre{isM} isP |-> istreamR 1$m isM
+    \arg{strP} "" (Vptr strP)
+    \pre{strM} strP |-> cppStringR 1$m strM
+    \post[Vptr isP]
+      Exists isM' strM',
+      isP |-> istreamR 1$m isM' **
+      strP |-> cppStringR 1$m strM' (* TODO: this is not precise enough *)
+  ).
+  (* Print istream_take_spec .
+  Print _inststd_dot__opgreatergreater_with_and_cons_ref_named_inststd_dot_basic__istream_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_nil_cons_ref_named_inststd_dot_____cxx11_dot_basic__string_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_nil_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_spec. *)
+(* The following dependencies are missing specifications:
+"std::endl<char, std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&)"%cpp_name
+"std::cin"%cpp_name
+"std::cout"%cpp_name
+
+"std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name
+"std::operator<<<char, std::char_traits<char>, std::allocator<char>>(std::basic_ostream<char, std::char_traits<char>>&, const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name
+"std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::~basic_string()"%cpp_name
+"std::basic_ostream<char, std::char_traits<char>>::operator<<(std::basic_ostream<char, std::char_traits<char>>&(*)(std::basic_ostream<char, std::char_traits<char>>&))"%cpp_name
+"std::basic_istream<char, std::char_traits<char>>::operator>>(int&)"%cpp_name
+"std::basic_ostream<char, std::char_traits<char>>::operator<<(int)"%cpp_name *)
+
+  Lemma main_ok : istream_take_spec |-- verify?[source] main_spec.
+  Proof.
+    verify_spec; go.
+  Qed.
+
+End with_cpp.
+

From c66d8e7f4900ce5cf0f32ec814157ec982a10e2e Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 16:47:47 +0100
Subject: [PATCH 07/21] Completed simpler example

---
 .../geeks_for_geeks_examples/N2_input.cpp     | 32 ++++-----
 .../test/geeks_for_geeks_examples/N2_input.v  | 72 +++++++++++++++----
 2 files changed, 73 insertions(+), 31 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
index 1da1f13..222f99c 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
@@ -3,22 +3,22 @@
 #include <iostream>
 using namespace std;
 
-// int main(){
-//     int i;
-//     // Take input using cin
-//     cin >> i;
-//     // Print output
-//     cout << i;
-//     return 0;
-// }
-
-int main() {
-    string name;
-    int age;
-    // Take multiple input using cin
-    cin >> name >> age;
+int main(){
+    int i;
+    // Take input using cin
+    cin >> i;
     // Print output
-    cout << "Name : " << name << endl;
-    cout << "Age : " << age << endl;
+    cout << i;
     return 0;
 }
+
+// int main() {
+//     string name;
+//     int age;
+//     // Take multiple input using cin
+//     cin >> name >> age;
+//     // Print output
+//     cout << "Name : " << name << endl;
+//     cout << "Age : " << age << endl;
+//     return 0;
+// }
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
index b3de793..b9572ad 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
@@ -3,31 +3,29 @@ Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N2_input_cpp.
 
+Import linearity.
+
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
   Parameter istreamT : Type.
   Parameter istreamR : cQp.t -> istreamT -> Rep.
-  (* Parameter istream_contentR : cQp.t -> cstring.t -> Rep. *)
+  #[global] Instance: LearnEqF1 istreamR := ltac:(solve_learnable).
 
-  cpp.spec "main()" from N2_input_cpp.source as main_spec with (
-    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
-    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
-    \post[Vint 0]
-      _global "std::cout" |-> ostream_contentR 1$m (str ++ "Hello World")).
+  (* Parameter istream_contentR : cQp.t -> cstring.t -> Rep. *)
 
   (* cpp.spec "puts" from source as puts_spec with (
     \arg{p} "" (Vptr p)
     \prepost{q s} p |-> cstring.R q s
     \post{n}[Vint n] emp). *)
-
+(*
   Parameter cppStringR : cQp.t -> cstring.t -> Rep.
   cpp.spec "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::basic_string()" from source as string_ctor_spec with (
     \this this
     \post this |-> cppStringR 1$m "").
 
-  #[global] Declare Instance cppStringR_typed : Typed2 "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>" cppStringR.
-
+  #[global] Declare Instance cppStringR_typed : Typed2 "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>" cppStringR. *)
+(*
   #[ignore_missing]
   cpp.spec
   "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"
@@ -42,8 +40,56 @@ Section with_cpp.
       isP |-> istreamR 1$m isM' **
       strP |-> cppStringR 1$m strM' (* TODO: this is not precise enough *)
   ).
-  (* Print istream_take_spec .
-  Print _inststd_dot__opgreatergreater_with_and_cons_ref_named_inststd_dot_basic__istream_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_nil_cons_ref_named_inststd_dot_____cxx11_dot_basic__string_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_nil_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_spec. *)
+  Print istream_take_char_spec . *)
+
+  cpp.spec "std::basic_istream<char, std::char_traits<char>>::operator>>(int&)" from source as istream_take_int_spec with (
+    \this this
+    \pre{isM} this |-> istreamR 1$m isM
+    \arg{nP} "" (Vptr nP)
+    \pre nP |-> anyR "int" 1$m
+    \post[Vptr this]
+      Exists isM' n,
+      this |-> istreamR 1$m isM' **
+      nP |-> intR 1$m n (* TODO: this is not precise enough *)
+  ).
+
+  Parameter Z_to_string : Z -> cstring.t.
+  (** TODO: find an implementation!*)
+
+  cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(int)" from source as ostream_print_int_spec with (
+    \this this
+    \prepost{osM} this |-> ostreamR 1$m osM
+    \pre{str} this |-> ostream_contentR 1$m str
+    \arg{n} "" (Vint n)
+    \post[Vptr this]
+        this |-> ostream_contentR 1$m (str ++ Z_to_string n)
+  ).
+
+  cpp.spec "main()" from N2_input_cpp.source as main_spec with (
+    \pre{isM} _global "std::cin" |-> istreamR 1$m isM
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      (* TODO: this is not precise enough *)
+      Exists n isM',
+        _global "std::cin" |-> istreamR 1$m isM' **
+        _global "std::cout" |-> ostream_contentR 1$m (str ++ Z_to_string n)
+      ).
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+
+    verify_spec; go.
+    ework with br_erefl.
+  Qed.
+
+(* The following dependencies are missing specifications:
+"std::cin"%cpp_name
+"std::cout"%cpp_name
+"std::basic_istream<char, std::char_traits<char>>::operator>>(int&)"%cpp_name
+"std::basic_ostream<char, std::char_traits<char>>::operator<<(int)"%cpp_name *)
+
+  (* Print _inststd_dot__opgreatergreater_with_and_cons_ref_named_inststd_dot_basic__istream_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_nil_cons_ref_named_inststd_dot_____cxx11_dot_basic__string_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_nil_with_cons_char_cons_named_inststd_dot_char__traits_with_cons_char_nil_cons_named_inststd_dot_allocator_with_cons_char_nil_nil_spec. *)
 (* The following dependencies are missing specifications:
 "std::endl<char, std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&)"%cpp_name
 "std::cin"%cpp_name
@@ -56,10 +102,6 @@ Section with_cpp.
 "std::basic_istream<char, std::char_traits<char>>::operator>>(int&)"%cpp_name
 "std::basic_ostream<char, std::char_traits<char>>::operator<<(int)"%cpp_name *)
 
-  Lemma main_ok : istream_take_spec |-- verify?[source] main_spec.
-  Proof.
-    verify_spec; go.
-  Qed.
 
 End with_cpp.
 

From 5e573b132c53a07c34f87ff2d7ef70e559505ecb Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 17:01:05 +0100
Subject: [PATCH 08/21] WIP towards full example

---
 .../geeks_for_geeks_examples/N2_input.cpp     | 24 +++++++++++++++----
 .../test/geeks_for_geeks_examples/N2_input.v  | 14 +++++------
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
index 222f99c..344291d 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
@@ -3,15 +3,29 @@
 #include <iostream>
 using namespace std;
 
-int main(){
-    int i;
-    // Take input using cin
-    cin >> i;
+// int main(){
+//     int i;
+//     // Take input using cin
+//     cin >> i;
+//     // Print output
+//     cout << i;
+//     return 0;
+// }
+
+int main() {
+    int age;
+    cin >> age;
+    string name;
+    // Take multiple input using cin
+    cin >> name;
+    // cin >> name >> age;
     // Print output
-    cout << i;
+    cout << "Name : " << name << endl;
+    cout << "Age : " << age << endl;
     return 0;
 }
 
+
 // int main() {
 //     string name;
 //     int age;
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
index b9572ad..9df5e31 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
@@ -18,13 +18,6 @@ Section with_cpp.
     \arg{p} "" (Vptr p)
     \prepost{q s} p |-> cstring.R q s
     \post{n}[Vint n] emp). *)
-(*
-  Parameter cppStringR : cQp.t -> cstring.t -> Rep.
-  cpp.spec "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::basic_string()" from source as string_ctor_spec with (
-    \this this
-    \post this |-> cppStringR 1$m "").
-
-  #[global] Declare Instance cppStringR_typed : Typed2 "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>" cppStringR. *)
 (*
   #[ignore_missing]
   cpp.spec
@@ -76,6 +69,13 @@ Section with_cpp.
         _global "std::cout" |-> ostream_contentR 1$m (str ++ Z_to_string n)
       ).
 
+  Parameter cppStringR : cQp.t -> cstring.t -> Rep.
+  cpp.spec "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::basic_string()" from source as string_ctor_spec with (
+    \this this
+    \post this |-> cppStringR 1$m "").
+
+  #[global] Declare Instance cppStringR_typed : Typed2 "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>" cppStringR.
+
   Lemma main_ok : verify?[source] main_spec.
   Proof.
 

From 9231a51a1e591aa681ac7365a0656a4108a2226f Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 10 Feb 2026 17:53:28 +0100
Subject: [PATCH 09/21] more examples

---
 .../geeks_for_geeks_examples/N2_input.cpp     |  2 +-
 .../test/geeks_for_geeks_examples/N2_input.v  | 47 ++++++++++++-------
 2 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
index 344291d..6e03f51 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
@@ -3,7 +3,7 @@
 #include <iostream>
 using namespace std;
 
-// int main(){
+// int main() {
 //     int i;
 //     // Take input using cin
 //     cin >> i;
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
index 9df5e31..e4bf587 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
@@ -18,22 +18,8 @@ Section with_cpp.
     \arg{p} "" (Vptr p)
     \prepost{q s} p |-> cstring.R q s
     \post{n}[Vint n] emp). *)
-(*
-  #[ignore_missing]
-  cpp.spec
-  "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"
-  from source as istream_take_char_spec with (
-  (* cpp.spec "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)" from source with ( *)
-    \arg{isP} "" (Vptr isP)
-    \pre{isM} isP |-> istreamR 1$m isM
-    \arg{strP} "" (Vptr strP)
-    \pre{strM} strP |-> cppStringR 1$m strM
-    \post[Vptr isP]
-      Exists isM' strM',
-      isP |-> istreamR 1$m isM' **
-      strP |-> cppStringR 1$m strM' (* TODO: this is not precise enough *)
-  ).
-  Print istream_take_char_spec . *)
+
+  Parameter cppStringR : cQp.t -> cstring.t -> Rep.
 
   cpp.spec "std::basic_istream<char, std::char_traits<char>>::operator>>(int&)" from source as istream_take_int_spec with (
     \this this
@@ -69,7 +55,6 @@ Section with_cpp.
         _global "std::cout" |-> ostream_contentR 1$m (str ++ Z_to_string n)
       ).
 
-  Parameter cppStringR : cQp.t -> cstring.t -> Rep.
   cpp.spec "std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::basic_string()" from source as string_ctor_spec with (
     \this this
     \post this |-> cppStringR 1$m "").
@@ -80,8 +65,34 @@ Section with_cpp.
   Proof.
 
     verify_spec; go.
-    ework with br_erefl.
+    (* progress ework with br_erefl. *)
+    set name := "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name.
+    exfalso.
+    clear.
+Set Printing All.
+Check "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name.
+Eval cbv in ("std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name).
+(* Print "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name. *)
+
   Qed.
+(* Print "std::operator() <char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"%cpp_name. *)
+
+  (* #[ignore_missing] *)
+  cpp.spec
+  "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)"
+  from N2_input_cpp.source as istream_take_char_spec with (
+  (* cpp.spec "std::operator>><char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&)" from source with ( *)
+    \arg{isP} "" (Vptr isP)
+    \pre{isM} isP |-> istreamR 1$m isM
+    \arg{strP} "" (Vptr strP)
+    \pre{strM} strP |-> cppStringR 1$m strM
+    \post[Vptr isP]
+      Exists isM' strM',
+      isP |-> istreamR 1$m isM' **
+      strP |-> cppStringR 1$m strM' (* TODO: this is not precise enough *)
+  ).
+  Print istream_take_char_spec .
+
 
 (* The following dependencies are missing specifications:
 "std::cin"%cpp_name

From 970a14fb8d93da4d360b81a2f0932639caf87931 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Wed, 11 Feb 2026 17:09:26 +0100
Subject: [PATCH 10/21] Upstreaming some specs a bit

---
 .../test/geeks_for_geeks_examples/N2_input.v  | 17 +-----------
 .../test/geeks_for_geeks_examples/spec.v      | 27 +++++++++++++++++++
 2 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
index e4bf587..a22b7cb 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
@@ -8,10 +8,6 @@ Import linearity.
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
-  Parameter istreamT : Type.
-  Parameter istreamR : cQp.t -> istreamT -> Rep.
-  #[global] Instance: LearnEqF1 istreamR := ltac:(solve_learnable).
-
   (* Parameter istream_contentR : cQp.t -> cstring.t -> Rep. *)
 
   (* cpp.spec "puts" from source as puts_spec with (
@@ -19,6 +15,7 @@ Section with_cpp.
     \prepost{q s} p |-> cstring.R q s
     \post{n}[Vint n] emp). *)
 
+  (** TODO: the model is bigger than cstring.t: just a list of "characters". *)
   Parameter cppStringR : cQp.t -> cstring.t -> Rep.
 
   cpp.spec "std::basic_istream<char, std::char_traits<char>>::operator>>(int&)" from source as istream_take_int_spec with (
@@ -32,18 +29,6 @@ Section with_cpp.
       nP |-> intR 1$m n (* TODO: this is not precise enough *)
   ).
 
-  Parameter Z_to_string : Z -> cstring.t.
-  (** TODO: find an implementation!*)
-
-  cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(int)" from source as ostream_print_int_spec with (
-    \this this
-    \prepost{osM} this |-> ostreamR 1$m osM
-    \pre{str} this |-> ostream_contentR 1$m str
-    \arg{n} "" (Vint n)
-    \post[Vptr this]
-        this |-> ostream_contentR 1$m (str ++ Z_to_string n)
-  ).
-
   cpp.spec "main()" from N2_input_cpp.source as main_spec with (
     \pre{isM} _global "std::cin" |-> istreamR 1$m isM
     \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index 9321767..bcc48b1 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -10,6 +10,16 @@ Require Export skylabs.cpp.string.
 
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.iostream_cpp.
 
+(** TODO upstream to bytestring *)
+#[global] Instance BS_append_inj_r x : Inj eq eq (BS.append x).
+Proof.
+  elim: x => [|x xs /= IH] [|y1 ys1] [|y2 ys2] //= [/(inj (BS.append _))] //.
+Qed.
+
+#[global] Instance refine_bs_app' (str a b : BS.t) :
+  Refine1 true true (str ++ a = str ++ b)%bs [a = b].
+Proof. tac_refine. move: H. apply: inj. Qed.
+
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
@@ -20,6 +30,10 @@ Section with_cpp.
   #[global] Instance: LearnEqF1 ostreamR := ltac:(solve_learnable).
   #[global] Instance: LearnEqF1 ostream_contentR := ltac:(solve_learnable).
 
+  Parameter istreamT : Type.
+  Parameter istreamR : cQp.t -> istreamT -> Rep.
+  #[global] Instance: LearnEqF1 istreamR := ltac:(solve_learnable).
+
   cpp.spec "std::operator<<<std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&, const char*)" from source as ostream_insert_spec with (
     \arg{osP} "" (Vptr osP)
     \prepost{osM} osP |-> ostreamR 1$m osM
@@ -29,4 +43,17 @@ Section with_cpp.
     \post[Vptr osP]
       osP |-> ostream_contentR 1$m (str ++ strM)).
 
+  Parameter Z_to_string : Z -> cstring.t.
+  #[global] Declare Instance Z_to_string_inj : Inj eq eq Z_to_string.
+  (** TODO: find an implementation!*)
+
+  cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(int)" from source as ostream_print_int_spec with (
+    \this this
+    \prepost{osM} this |-> ostreamR 1$m osM
+    \pre{str} this |-> ostream_contentR 1$m str
+    \arg{n} "" (Vint n)
+    \post[Vptr this]
+        this |-> ostream_contentR 1$m (str ++ Z_to_string n)
+  ).
+
 End with_cpp.

From 3472ceb00a9a6e7725320b88c7ce89e9f66d389f Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Wed, 11 Feb 2026 17:09:54 +0100
Subject: [PATCH 11/21] More examples, with a loop invariant

Example 5

iostream spec: Let stream manipulators modify stream state

Upstream specs

More examples

Rephrase proofs for aggressive hint

Improve spec
---
 rocq-brick-libstdcpp/test/dune.inc            | 45 +++++++++++++++
 .../geeks_for_geeks_examples/N12_area.cpp     | 30 ++++++++++
 .../test/geeks_for_geeks_examples/N12_area.v  | 37 ++++++++++++
 .../test/geeks_for_geeks_examples/N3_sum.cpp  | 11 ++++
 .../test/geeks_for_geeks_examples/N3_sum.v    | 20 +++++++
 .../geeks_for_geeks_examples/N3_sum_a.cpp     | 18 ++++++
 .../test/geeks_for_geeks_examples/N3_sum_a.v  | 37 ++++++++++++
 .../test/geeks_for_geeks_examples/N5_swap.cpp | 17 ++++++
 .../test/geeks_for_geeks_examples/N5_swap.v   | 44 ++++++++++++++
 .../N6_print_sizeof.cpp                       | 31 ++++++++++
 .../N6_print_sizeof.v                         | 35 ++++++++++++
 .../test/geeks_for_geeks_examples/spec.v      | 57 +++++++++++++++++++
 12 files changed, 382 insertions(+)
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.v
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.v

diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index a5b255d..f708dd5 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -26,6 +26,15 @@
                          (run cpp2v -v %{input} -o N0_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps N0_hello_world.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N12_area_cpp.v)
+  (alias test_ast)
+  (deps (:input N12_area.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N12_area_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N12_area.cpp))
+)
 (subdir geeks_for_geeks_examples
  (rule
   (targets N2_input_cpp.v)
@@ -35,6 +44,42 @@
                          (run cpp2v -v %{input} -o N2_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps N2_input.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N3_sum_cpp.v)
+  (alias test_ast)
+  (deps (:input N3_sum.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N3_sum_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N3_sum.cpp))
+)
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N3_sum_a_cpp.v)
+  (alias test_ast)
+  (deps (:input N3_sum_a.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N3_sum_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N3_sum_a.cpp))
+)
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N5_swap_cpp.v)
+  (alias test_ast)
+  (deps (:input N5_swap.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N5_swap_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N5_swap.cpp))
+)
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N6_print_sizeof_cpp.v)
+  (alias test_ast)
+  (deps (:input N6_print_sizeof.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N6_print_sizeof_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N6_print_sizeof.cpp))
+)
 (subdir geeks_for_geeks_examples
  (rule
   (targets iostream_cpp.v)
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.cpp
new file mode 100644
index 0000000..ccbab26
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.cpp
@@ -0,0 +1,30 @@
+// C++ program to find area
+// and perimeter of rectangle
+#include<iostream>
+using namespace std;
+
+// Utility function
+int areaRectangle(int a, int b)
+{
+   int area = a * b;
+   return area;
+}
+
+int perimeterRectangle(int a, int b)
+{
+   int perimeter = 2*(a + b);
+   return perimeter;
+}
+
+// Driver code
+int main()
+{
+  int a = 5;
+  int b = 6;
+  cout << "Area = " <<
+           areaRectangle(a, b) <<
+           endl;
+  cout << "Perimeter = " <<
+           perimeterRectangle(a, b);
+  return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.v
new file mode 100644
index 0000000..0570fac
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N12_area.v
@@ -0,0 +1,37 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N12_area_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  Definition area_of_rectangle (side1 side2 : Z) := side1 * side2.
+  Definition perimeter_of_rectangle (side1 side2 : Z) := 2 * (side1 + side2).
+  Definition side1 := 5.
+  Definition side2 := 6.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m
+        (str ++ "Area = " ++ Z_to_string (area_of_rectangle side1 side2) ++ "\n" ++ "Perimeter = " ++ Z_to_string (perimeter_of_rectangle side1 side2))
+  ).
+
+  cpp.spec "areaRectangle(int, int)" from source inline.
+  cpp.spec "perimeterRectangle(int, int)" from source inline.
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_shift; go.
+    iExists (_ : ostreamT → ostreamT), (_ : cstring.t → cstring.t); work with br_erefl; go.
+
+    banish_string_literals.
+    iModIntro.
+    work.
+    by rewrite -!(assoc_L BS.append).
+  Qed.
+End with_cpp.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp
new file mode 100644
index 0000000..f0bf9b0
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp
@@ -0,0 +1,11 @@
+#include <iostream>
+using namespace std;
+
+int main() {
+    int a = 11, b = 9;
+
+    // Adding the two numbers and printing
+    // their sum
+    cout << a + b;
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v
new file mode 100644
index 0000000..e62a246
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v
@@ -0,0 +1,20 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N3_sum_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m (str ++ Z_to_string 20)
+  ).
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof. verify_spec; go. Qed.
+End with_cpp.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp
new file mode 100644
index 0000000..9323d4c
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp
@@ -0,0 +1,18 @@
+#include <iostream>
+using namespace std;
+
+int main() {
+    int a = 11, b = 9;
+
+    // If b is positive, increment a to b times
+    for (int i = 0; i < b; i++)
+        a++;
+
+    // If b is negative, decrement a to |b| times
+    for (int i = 0; i > b; i--)
+        a--;
+
+    cout << a;
+
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v
new file mode 100644
index 0000000..d6047de
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v
@@ -0,0 +1,37 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N3_sum_a_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m (str ++ Z_to_string 20)
+  ).
+
+  #[global] Declare Instance Z_to_string_inj : Inj eq eq Z_to_string.
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_spec; go.
+
+    wp_for (fun ρ =>
+      \pre{i1} _local ρ "i" |-> intR 1$m i1
+      \pre _local ρ "a" |-> intR 1$m (11 + i1)
+      \require 0 <= i1 <= 9
+      \post* _local ρ "i" |-> anyR "int" 1$m
+      \post* _local ρ "a" |-> intR 1$m 20
+      \post emp
+    ).
+
+    go.
+    wp_if; go.
+    wp_for (fun ρ => emp); go.
+  Qed.
+End with_cpp.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
new file mode 100644
index 0000000..e1e67d6
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
@@ -0,0 +1,17 @@
+// https://www.geeksforgeeks.org/cpp/cpp-program-to-swap-two-numbers/
+#include <iostream>
+using namespace std;
+
+int main(){
+    int a = 2, b = 3;
+
+    cout << "Before swapping a = " << a << " , b = " << b << endl;
+
+    int temp;
+
+    temp = a;
+    a = b;
+    b = temp;
+    cout << "After swapping a = " << a << " , b = " << b << endl;
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
new file mode 100644
index 0000000..3e02a3a
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
@@ -0,0 +1,44 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N5_swap_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m
+        (str ++
+        "Before swapping a = " ++
+        Z_to_string 2 ++ " , b = " ++ Z_to_string 3 ++ "\n" ++
+        "After swapping a = " ++ Z_to_string 3 ++ " , b = " ++ Z_to_string 2 ++ "\n"
+      )
+  ).
+
+  #[program]
+  Definition hint_stream_F :=
+    \cancelx@{mpredI}
+    \bound_existential (stream_f : cstring.t → cstring.t)
+    \bound_existential (state_f : ostreamT → ostreamT)
+    \instantiate stream_f := fun str => (str ++ "\n")%bs
+    \instantiate state_f := fun osM => osM
+    \end.
+  Next Obligation. work. Qed.
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_shift; go.
+    (* iExists id, (fun str => str ++ "\n")%bs; go. *)
+    iExists (_ : ostreamT → ostreamT), (_ : cstring.t → cstring.t); work with br_erefl; go.
+    iExists (_ : ostreamT → ostreamT), (_ : cstring.t → cstring.t); work with br_erefl; go.
+    banish_string_literals.
+    iModIntro.
+    work.
+    by rewrite -!(assoc_L BS.append).
+  Qed.
+End with_cpp.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.cpp
new file mode 100644
index 0000000..8e82db0
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.cpp
@@ -0,0 +1,31 @@
+#include <iostream>
+using namespace std;
+
+int main()
+{
+    int integerType;
+    char charType;
+    float floatType;
+    double doubleType;
+
+    // Calculate and Print
+    // the size of integer type
+    cout << "Size of int is: " << sizeof(integerType)
+         << "\n";
+
+    // Calculate and Print
+    // the size of doubleType
+    cout << "Size of char is: " << sizeof(charType) << "\n";
+
+    // Calculate and Print
+    // the size of charType
+    cout << "Size of float is: " << sizeof(floatType)
+         << "\n";
+
+    // Calculate and Print
+    // the size of floatType
+    cout << "Size of double is: " << sizeof(doubleType)
+         << "\n";
+
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.v
new file mode 100644
index 0000000..e476f45
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N6_print_sizeof.v
@@ -0,0 +1,35 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N6_print_sizeof_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  Definition newline := "
+"%bs.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m
+        (str ++
+        "Size of int is: " ++ Z_to_string 4 ++ newline ++
+        "Size of char is: " ++ Z_to_string 1 ++ newline ++
+        "Size of float is: " ++ Z_to_string 4 ++ newline ++
+        "Size of double is: " ++ Z_to_string 8 ++ newline)
+  ).
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_shift; go.
+
+    banish_string_literals.
+    iModIntro.
+    work.
+    by rewrite -!(assoc_L BS.append).
+  Qed.
+End with_cpp.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index bcc48b1..c7e640e 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -16,10 +16,17 @@ Proof.
   elim: x => [|x xs /= IH] [|y1 ys1] [|y2 ys2] //= [/(inj (BS.append _))] //.
 Qed.
 
+#[global] Instance BS_append_assoc : Assoc eq BS.append.
+Proof.
+  elim => [|x xs IH] [|y ys] [|z zs] //=. all: by rewrite -IH.
+Qed.
+
 #[global] Instance refine_bs_app' (str a b : BS.t) :
   Refine1 true true (str ++ a = str ++ b)%bs [a = b].
 Proof. tac_refine. move: H. apply: inj. Qed.
 
+#[global] Arguments BS.append : simpl never.
+
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
@@ -56,4 +63,54 @@ Section with_cpp.
         this |-> ostream_contentR 1$m (str ++ Z_to_string n)
   ).
 
+  cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(unsigned long)" from source as ostream_print_ulong_spec with (
+    \this this
+    \prepost{osM} this |-> ostreamR 1$m osM
+    \pre{str} this |-> ostream_contentR 1$m str
+    \arg{n} "" (Vint n)
+    \post[Vptr this]
+        this |-> ostream_contentR 1$m (str ++ Z_to_string n)
+  ).
+
+  Definition iostream_manip_spec state_f contents_f : WpSpec_cpp_val := (
+    \arg{osP : ptr} "" (Vptr osP)
+    (* XXX: manipulators can modify [osM]! *)
+    \pre{osM} osP |-> ostreamR 1$m osM
+    \post* osP |-> ostreamR 1$m (state_f osM)
+    \pre{str} osP |-> ostream_contentR 1$m str
+    \post[Vptr osP] osP |-> ostream_contentR 1$m (contents_f str)).
+
+  Definition ostream_cpp_type : type :=
+    "std::basic_ostream<char, std::char_traits<char>>&".
+  Definition iostream_manip_kind : okind :=
+    tFunction ostream_cpp_type [ostream_cpp_type].
+
+  cpp.spec "std::endl<char, std::char_traits<char>>(std::basic_ostream<char, std::char_traits<char>>&)" from source as endl_spec with (
+    \exact Reduce iostream_manip_spec (fun osM => osM) (fun str => str ++ "\n")%bs
+  ).
+
+  (* This is the overload taking the endl manipulator. *)
+  cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(std::basic_ostream<char, std::char_traits<char>>&(*)(std::basic_ostream<char, std::char_traits<char>>&))" from source as ostream_insert_string_spec with (
+    \this this
+    \arg{os_f} "" (Vptr os_f)
+    \pre{state_f stream_f}
+      os_f |-> unmaterialized_specR
+        iostream_manip_kind
+        (iostream_manip_spec state_f stream_f)
+    \pre{osM} this |-> ostreamR 1$m osM
+    \post* this |-> ostreamR 1$m (state_f osM)
+    \pre{str} this |-> ostream_contentR 1$m str
+    \post[Vptr this]
+      this |-> ostream_contentR 1$m (stream_f str)
+  ).
+
+  Lemma ostream_contentR_aggressive (os_p : ptr) q str str':
+    os_p |-> ostream_contentR q str ⊢
+    [| str = str' |] -∗
+    os_p |-> ostream_contentR q str'.
+  Proof. work. Qed.
+  Definition ostream_contentR_aggressiveC := [CANCEL] ostream_contentR_aggressive.
+
 End with_cpp.
+
+#[export] Hint Resolve ostream_contentR_aggressiveC : br_hints.

From 5d26e23a8ccea67a8f776c4a5f06b28cf9015a21 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Thu, 12 Feb 2026 17:13:08 +0100
Subject: [PATCH 12/21] Fix numbers

---
 rocq-brick-libstdcpp/test/dune.inc            | 58 ++++++++++++-------
 ...{N0_hello_world.cpp => N1_hello_world.cpp} |  0
 .../{N0_hello_world.v => N1_hello_world.v}    |  2 +-
 .../{N2_input.cpp => N3_input.cpp}            |  0
 .../{N2_input.v => N3_input.v}                |  2 +-
 .../{N3_sum.cpp => N4_sum.cpp}                |  0
 .../{N3_sum.v => N4_sum.v}                    |  2 +-
 .../{N3_sum_a.cpp => N4_sum_a.cpp}            |  0
 .../{N3_sum_a.v => N4_sum_a.v}                |  2 +-
 9 files changed, 42 insertions(+), 24 deletions(-)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N0_hello_world.cpp => N1_hello_world.cpp} (100%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N0_hello_world.v => N1_hello_world.v} (96%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N2_input.cpp => N3_input.cpp} (100%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N2_input.v => N3_input.v} (99%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N3_sum.cpp => N4_sum.cpp} (100%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N3_sum.v => N4_sum.v} (97%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N3_sum_a.cpp => N4_sum_a.cpp} (100%)
 rename rocq-brick-libstdcpp/test/geeks_for_geeks_examples/{N3_sum_a.v => N4_sum_a.v} (98%)

diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index f708dd5..b4ecf39 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -19,48 +19,48 @@
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N0_hello_world_cpp.v)
+  (targets N12_area_cpp.v)
   (alias test_ast)
-  (deps (:input N0_hello_world.cpp) (glob_files_rec ../*.hpp) (universe))
+  (deps (:input N12_area.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N0_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
- (alias (name srcs) (deps N0_hello_world.cpp))
+                         (run cpp2v -v %{input} -o N12_area_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N12_area.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N12_area_cpp.v)
+  (targets N1_hello_world_cpp.v)
   (alias test_ast)
-  (deps (:input N12_area.cpp) (glob_files_rec ../*.hpp) (universe))
+  (deps (:input N1_hello_world.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N12_area_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
- (alias (name srcs) (deps N12_area.cpp))
+                         (run cpp2v -v %{input} -o N1_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N1_hello_world.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N2_input_cpp.v)
+  (targets N3_input_cpp.v)
   (alias test_ast)
-  (deps (:input N2_input.cpp) (glob_files_rec ../*.hpp) (universe))
+  (deps (:input N3_input.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N2_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
- (alias (name srcs) (deps N2_input.cpp))
+                         (run cpp2v -v %{input} -o N3_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N3_input.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N3_sum_cpp.v)
+  (targets N4_sum_cpp.v)
   (alias test_ast)
-  (deps (:input N3_sum.cpp) (glob_files_rec ../*.hpp) (universe))
+  (deps (:input N4_sum.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N3_sum_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
- (alias (name srcs) (deps N3_sum.cpp))
+                         (run cpp2v -v %{input} -o N4_sum_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N4_sum.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N3_sum_a_cpp.v)
+  (targets N4_sum_a_cpp.v)
   (alias test_ast)
-  (deps (:input N3_sum_a.cpp) (glob_files_rec ../*.hpp) (universe))
+  (deps (:input N4_sum_a.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N3_sum_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
- (alias (name srcs) (deps N3_sum_a.cpp))
+                         (run cpp2v -v %{input} -o N4_sum_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N4_sum_a.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
@@ -80,6 +80,24 @@
                          (run cpp2v -v %{input} -o N6_print_sizeof_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
  (alias (name srcs) (deps N6_print_sizeof.cpp))
 )
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N8_ascii_value_cast_cpp.v)
+  (alias test_ast)
+  (deps (:input N8_ascii_value_cast.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N8_ascii_value_cast_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N8_ascii_value_cast.cpp))
+)
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N8_ascii_value_printf_cpp.v)
+  (alias test_ast)
+  (deps (:input N8_ascii_value_printf.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+                         (run cpp2v -v %{input} -o N8_ascii_value_printf_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+ (alias (name srcs) (deps N8_ascii_value_printf.cpp))
+)
 (subdir geeks_for_geeks_examples
  (rule
   (targets iostream_cpp.v)
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.cpp
similarity index 100%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.cpp
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.cpp
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
similarity index 96%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
index 21fd44d..2dabb26 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N0_hello_world.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
@@ -1,7 +1,7 @@
 Require Import skylabs.auto.cpp.prelude.proof.
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
-Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N0_hello_world_cpp.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N1_hello_world_cpp.
 
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.cpp
similarity index 100%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.cpp
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.cpp
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
similarity index 99%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
index a22b7cb..d911790 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N2_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
@@ -1,7 +1,7 @@
 Require Import skylabs.auto.cpp.prelude.proof.
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
-Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N2_input_cpp.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N3_input_cpp.
 
 Import linearity.
 
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp
similarity index 100%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.cpp
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.v
similarity index 97%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.v
index e62a246..fd17459 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.v
@@ -1,7 +1,7 @@
 Require Import skylabs.auto.cpp.prelude.proof.
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
-Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N3_sum_cpp.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N4_sum_cpp.
 
 Import linearity.
 
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp
similarity index 100%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.cpp
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.v
similarity index 98%
rename from rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v
rename to rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.v
index d6047de..f5bad0c 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_sum_a.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.v
@@ -1,7 +1,7 @@
 Require Import skylabs.auto.cpp.prelude.proof.
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
 
-Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N3_sum_a_cpp.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N4_sum_a_cpp.
 
 Import linearity.
 

From 4fe5cd716758aba601a8de0573705ad7614a838e Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Thu, 12 Feb 2026 17:15:33 +0100
Subject: [PATCH 13/21] Missing URLs

---
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp   | 2 ++
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp | 2 ++
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp  | 1 +
 3 files changed, 5 insertions(+)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp
index f0bf9b0..b4c759e 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum.cpp
@@ -1,3 +1,5 @@
+// https://www.geeksforgeeks.org/cpp/cpp-add-numbers/
+
 #include <iostream>
 using namespace std;
 
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp
index 9323d4c..bbadd7f 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N4_sum_a.cpp
@@ -1,3 +1,5 @@
+// https://www.geeksforgeeks.org/cpp/cpp-add-numbers/, 2nd version
+
 #include <iostream>
 using namespace std;
 
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
index e1e67d6..b3b635d 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.cpp
@@ -1,4 +1,5 @@
 // https://www.geeksforgeeks.org/cpp/cpp-program-to-swap-two-numbers/
+
 #include <iostream>
 using namespace std;
 

From 70cd703538c57612d1cc3f82d54dc7ad4fe17233 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Fri, 13 Feb 2026 14:04:52 +0100
Subject: [PATCH 14/21] WIP readd stderr files

---
 rocq-brick-libstdcpp/proof/dune.inc | 36 ++++++++---------
 rocq-brick-libstdcpp/test/dune.inc  | 61 +++++++++++++++++------------
 2 files changed, 53 insertions(+), 44 deletions(-)

diff --git a/rocq-brick-libstdcpp/proof/dune.inc b/rocq-brick-libstdcpp/proof/dune.inc
index 4482e93..6d6db53 100644
--- a/rocq-brick-libstdcpp/proof/dune.inc
+++ b/rocq-brick-libstdcpp/proof/dune.inc
@@ -1,82 +1,82 @@
 ; DO NOT EDIT: Generated by "./dune-gen.sh"
 (subdir cassert
  (rule
-  (targets inc_cassert_cpp.v)
+  (targets inc_cassert_cpp.v.stderr inc_cassert_cpp.v)
   (alias test_ast)
   (deps (:input inc_cassert.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_cassert_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_cassert_cpp.v.stderr (run cpp2v -v %{input} -o inc_cassert_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc_cassert.cpp))
 )
 (subdir cctype
  (rule
-  (targets inc_cctype_cpp.v)
+  (targets inc_cctype_cpp.v.stderr inc_cctype_cpp.v)
   (alias test_ast)
   (deps (:input inc_cctype.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_cctype_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_cctype_cpp.v.stderr (run cpp2v -v %{input} -o inc_cctype_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc_cctype.cpp))
 )
 (subdir cstdlib
  (rule
-  (targets inc_cstdlib_cpp.v)
+  (targets inc_cstdlib_cpp.v.stderr inc_cstdlib_cpp.v)
   (alias test_ast)
   (deps (:input inc_cstdlib.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_cstdlib_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_cstdlib_cpp.v.stderr (run cpp2v -v %{input} -o inc_cstdlib_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc_cstdlib.cpp))
 )
 (subdir mutex
  (rule
-  (targets demo_cpp.v)
+  (targets demo_cpp.v.stderr demo_cpp.v)
   (alias test_ast)
   (deps (:input demo.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to demo_cpp.v.stderr (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps demo.cpp))
 )
 (subdir mutex
  (rule
-  (targets inc_hpp.v)
+  (targets inc_hpp.v.stderr inc_hpp.v)
   (alias test_ast)
   (deps (:input inc.hpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_hpp.v.stderr (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc.hpp))
 )
 (subdir mutex
  (rule
-  (targets test_cpp.v)
+  (targets test_cpp.v.stderr test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps test.cpp))
 )
 (subdir new
  (rule
-  (targets inc_new_cpp.v)
+  (targets inc_new_cpp.v.stderr inc_new_cpp.v)
   (alias test_ast)
   (deps (:input inc_new.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_new_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_new_cpp.v.stderr (run cpp2v -v %{input} -o inc_new_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc_new.cpp))
 )
 (subdir semaphore
  (rule
-  (targets inc_hpp.v)
+  (targets inc_hpp.v.stderr inc_hpp.v)
   (alias test_ast)
   (deps (:input inc.hpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to inc_hpp.v.stderr (run cpp2v -v %{input} -o inc_hpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps inc.hpp))
 )
 (subdir semaphore
  (rule
-  (targets test_cpp.v)
+  (targets test_cpp.v.stderr test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps test.cpp))
 )
diff --git a/rocq-brick-libstdcpp/test/dune.inc b/rocq-brick-libstdcpp/test/dune.inc
index b4ecf39..88dc99a 100644
--- a/rocq-brick-libstdcpp/test/dune.inc
+++ b/rocq-brick-libstdcpp/test/dune.inc
@@ -1,118 +1,127 @@
 ; DO NOT EDIT: Generated by "./dune-gen.sh"
 (subdir cctype
  (rule
-  (targets test_cpp.v)
+  (targets test_cpp.v.stderr test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps test.cpp))
 )
 (subdir cstdlib
  (rule
-  (targets test_cpp.v)
+  (targets test_cpp.v.stderr test_cpp.v)
   (alias test_ast)
   (deps (:input test.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to test_cpp.v.stderr (run cpp2v -v %{input} -o test_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps test.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N12_area_cpp.v)
+  (targets N12_area_cpp.v.stderr N12_area_cpp.v)
   (alias test_ast)
   (deps (:input N12_area.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N12_area_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N12_area_cpp.v.stderr (run cpp2v -v %{input} -o N12_area_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N12_area.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N1_hello_world_cpp.v)
+  (targets N1_hello_world_cpp.v.stderr N1_hello_world_cpp.v)
   (alias test_ast)
   (deps (:input N1_hello_world.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N1_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N1_hello_world_cpp.v.stderr (run cpp2v -v %{input} -o N1_hello_world_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N1_hello_world.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N3_input_cpp.v)
+  (targets N3_input_cpp.v.stderr N3_input_cpp.v)
   (alias test_ast)
   (deps (:input N3_input.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N3_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N3_input_cpp.v.stderr (run cpp2v -v %{input} -o N3_input_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N3_input.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N4_sum_cpp.v)
+  (targets N4_sum_cpp.v.stderr N4_sum_cpp.v)
   (alias test_ast)
   (deps (:input N4_sum.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N4_sum_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N4_sum_cpp.v.stderr (run cpp2v -v %{input} -o N4_sum_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N4_sum.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N4_sum_a_cpp.v)
+  (targets N4_sum_a_cpp.v.stderr N4_sum_a_cpp.v)
   (alias test_ast)
   (deps (:input N4_sum_a.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N4_sum_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N4_sum_a_cpp.v.stderr (run cpp2v -v %{input} -o N4_sum_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N4_sum_a.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N5_swap_cpp.v)
+  (targets N5_swap_cpp.v.stderr N5_swap_cpp.v)
   (alias test_ast)
   (deps (:input N5_swap.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N5_swap_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N5_swap_cpp.v.stderr (run cpp2v -v %{input} -o N5_swap_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N5_swap.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N6_print_sizeof_cpp.v)
+  (targets N5_swap_a_cpp.v.stderr N5_swap_a_cpp.v)
+  (alias test_ast)
+  (deps (:input N5_swap_a.cpp) (glob_files_rec ../*.hpp) (universe))
+  (action
+  	 (with-stderr-to N5_swap_a_cpp.v.stderr (run cpp2v -v %{input} -o N5_swap_a_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
+ (alias (name srcs) (deps N5_swap_a.cpp))
+)
+(subdir geeks_for_geeks_examples
+ (rule
+  (targets N6_print_sizeof_cpp.v.stderr N6_print_sizeof_cpp.v)
   (alias test_ast)
   (deps (:input N6_print_sizeof.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N6_print_sizeof_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N6_print_sizeof_cpp.v.stderr (run cpp2v -v %{input} -o N6_print_sizeof_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N6_print_sizeof.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N8_ascii_value_cast_cpp.v)
+  (targets N8_ascii_value_cast_cpp.v.stderr N8_ascii_value_cast_cpp.v)
   (alias test_ast)
   (deps (:input N8_ascii_value_cast.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N8_ascii_value_cast_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N8_ascii_value_cast_cpp.v.stderr (run cpp2v -v %{input} -o N8_ascii_value_cast_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N8_ascii_value_cast.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets N8_ascii_value_printf_cpp.v)
+  (targets N8_ascii_value_printf_cpp.v.stderr N8_ascii_value_printf_cpp.v)
   (alias test_ast)
   (deps (:input N8_ascii_value_printf.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o N8_ascii_value_printf_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to N8_ascii_value_printf_cpp.v.stderr (run cpp2v -v %{input} -o N8_ascii_value_printf_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps N8_ascii_value_printf.cpp))
 )
 (subdir geeks_for_geeks_examples
  (rule
-  (targets iostream_cpp.v)
+  (targets iostream_cpp.v.stderr iostream_cpp.v)
   (alias test_ast)
   (deps (:input iostream.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o iostream_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to iostream_cpp.v.stderr (run cpp2v -v %{input} -o iostream_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps iostream.cpp))
 )
 (subdir new
  (rule
-  (targets demo_cpp.v)
+  (targets demo_cpp.v.stderr demo_cpp.v)
   (alias test_ast)
   (deps (:input demo.cpp) (glob_files_rec ../*.hpp) (universe))
   (action
-                         (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ )))
+  	 (with-stderr-to demo_cpp.v.stderr (run cpp2v -v %{input} -o demo_cpp.v --no-elaborate  -- -std=c++20 -stdlib=libstdc++ ))))
  (alias (name srcs) (deps demo.cpp))
 )

From aec0888ffbbf91324fb4b37c5bed6215eabe9084 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Fri, 13 Feb 2026 14:05:40 +0100
Subject: [PATCH 15/21] More name fixes

---
 .../test/geeks_for_geeks_examples/N1_hello_world.v              | 2 +-
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
index 2dabb26..9e773f6 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N1_hello_world.v
@@ -6,7 +6,7 @@ Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N1_hello_wo
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.
 
-  cpp.spec "main()" from N0_hello_world_cpp.source as main_spec with (
+  cpp.spec "main()" from source as main_spec with (
     \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
     \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
     \post[Vint 0]
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
index d911790..79a4dce 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N3_input.v
@@ -29,7 +29,7 @@ Section with_cpp.
       nP |-> intR 1$m n (* TODO: this is not precise enough *)
   ).
 
-  cpp.spec "main()" from N2_input_cpp.source as main_spec with (
+  cpp.spec "main()" from source as main_spec with (
     \pre{isM} _global "std::cin" |-> istreamR 1$m isM
     \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
     \pre{str} _global "std::cout" |-> ostream_contentR 1$m str

From 663d1bae89ff1c046bbe886789ab29d8769eb96b Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Fri, 13 Feb 2026 14:07:44 +0100
Subject: [PATCH 16/21] Add variant of example

---
 .../geeks_for_geeks_examples/N5_swap_a.cpp    | 15 ++++++++
 .../test/geeks_for_geeks_examples/N5_swap_a.v | 35 +++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.cpp
 create mode 100644 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.v

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.cpp b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.cpp
new file mode 100644
index 0000000..0866ce7
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.cpp
@@ -0,0 +1,15 @@
+#include <iostream>
+using namespace std;
+
+int main(){
+    int a = 2, b = 3;
+
+    cout << "Before swapping a = " << a << " , b = " << b << endl;
+
+    b = a + b;
+    a = b - a;
+    b = b - a;
+
+    cout << "After swapping a = " << a << " , b = " << b << endl;
+    return 0;
+}
diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.v
new file mode 100644
index 0000000..e7098f3
--- /dev/null
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap_a.v
@@ -0,0 +1,35 @@
+Require Import skylabs.auto.cpp.prelude.proof.
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.spec.
+
+Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.N5_swap_a_cpp.
+
+Import linearity.
+
+Section with_cpp.
+  Context `{Σ : cpp_logic, σ : genv}.
+
+  cpp.spec "main()" from source as main_spec with (
+    \prepost{osM} _global "std::cout" |-> ostreamR 1$m osM
+    \pre{str} _global "std::cout" |-> ostream_contentR 1$m str
+    \post[Vint 0]
+      _global "std::cout" |-> ostream_contentR 1$m
+        (str ++
+        "Before swapping a = " ++
+        Z_to_string 2 ++ " , b = " ++ Z_to_string 3 ++ "\n" ++
+        "After swapping a = " ++ Z_to_string 3 ++ " , b = " ++ Z_to_string 2 ++ "\n"
+      )
+  ).
+
+  Lemma main_ok : verify?[source] main_spec.
+  Proof.
+    verify_shift; go.
+    (* iExists id, (fun str => str ++ "\n")%bs; go. *)
+    iExists (_ : ostreamT → ostreamT), (_ : cstring.t → cstring.t); work with br_erefl; go.
+    iExists (_ : ostreamT → ostreamT), (_ : cstring.t → cstring.t); work with br_erefl; go.
+    banish_string_literals.
+    iModIntro.
+    work.
+    by rewrite -!(assoc_L BS.append).
+  Qed.
+End with_cpp.
+

From 9ebdaf5d7dcc71cfbc3b9d94a81c299a2004fc76 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Fri, 13 Feb 2026 14:09:21 +0100
Subject: [PATCH 17/21] Drop non-working hint

---
 .../test/geeks_for_geeks_examples/N5_swap.v            | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
index 3e02a3a..2cc46fa 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/N5_swap.v
@@ -20,16 +20,6 @@ Section with_cpp.
       )
   ).
 
-  #[program]
-  Definition hint_stream_F :=
-    \cancelx@{mpredI}
-    \bound_existential (stream_f : cstring.t → cstring.t)
-    \bound_existential (state_f : ostreamT → ostreamT)
-    \instantiate stream_f := fun str => (str ++ "\n")%bs
-    \instantiate state_f := fun osM => osM
-    \end.
-  Next Obligation. work. Qed.
-
   Lemma main_ok : verify?[source] main_spec.
   Proof.
     verify_shift; go.

From 6d3ec5e2f2a13e795c5ad66d4d2a5eed102718dd Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 17 Feb 2026 15:48:01 +0100
Subject: [PATCH 18/21] Annotate spec stability

---
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index c7e640e..021a40d 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -1,3 +1,10 @@
+(**
+Tentative iostreams specs.
+
+These are trace-based specifications, and there is a _wish_ to move to a
+different style of specifications.
+
+*)
 Require Import skylabs.auto.cpp.prelude.proof.
 Require Export skylabs.cpp.string.
 

From 5e54c3883a3e10d95539d1677f8741ed07ecdc53 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 17 Feb 2026 15:48:51 +0100
Subject: [PATCH 19/21] TODO fix buggy spec

---
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index 021a40d..c935096 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -97,6 +97,7 @@ Section with_cpp.
   ).
 
   (* This is the overload taking the endl manipulator. *)
+  (* https://eel.is/c++draft/output.streams#ostream.inserters *)
   cpp.spec "std::basic_ostream<char, std::char_traits<char>>::operator<<(std::basic_ostream<char, std::char_traits<char>>&(*)(std::basic_ostream<char, std::char_traits<char>>&))" from source as ostream_insert_string_spec with (
     \this this
     \arg{os_f} "" (Vptr os_f)

From 0ad249415656de6809ad76f8b985f781860864ed Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 17 Feb 2026 15:49:26 +0100
Subject: [PATCH 20/21] Tweak upstreamed code

---
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index c935096..b919038 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -18,14 +18,15 @@ Require Export skylabs.cpp.string.
 Require Import skylabs.brick.libstdcpp.test.geeks_for_geeks_examples.iostream_cpp.
 
 (** TODO upstream to bytestring *)
+#[global] Arguments BS.append !_ !_ /.
 #[global] Instance BS_append_inj_r x : Inj eq eq (BS.append x).
 Proof.
-  elim: x => [|x xs /= IH] [|y1 ys1] [|y2 ys2] //= [/(inj (BS.append _))] //.
+  elim: x => [|x xs /= IH] [|y1 ys1] [|y2 ys2] // [/(inj (BS.append _))] //.
 Qed.
 
 #[global] Instance BS_append_assoc : Assoc eq BS.append.
 Proof.
-  elim => [|x xs IH] [|y ys] [|z zs] //=. all: by rewrite -IH.
+  elim => [|x xs IH] [|y ys] [|z zs] //=; by rewrite -IH.
 Qed.
 
 #[global] Instance refine_bs_app' (str a b : BS.t) :

From a6e495d5d733112d906ec48bc3b015f7fb63f876 Mon Sep 17 00:00:00 2001
From: "Paolo G. Giarrusso" <paolo@skylabs-ai.com>
Date: Tue, 17 Feb 2026 15:49:33 +0100
Subject: [PATCH 21/21] Tweak code to upstream

---
 rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
index b919038..453ed76 100644
--- a/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
+++ b/rocq-brick-libstdcpp/test/geeks_for_geeks_examples/spec.v
@@ -29,11 +29,10 @@ Proof.
   elim => [|x xs IH] [|y ys] [|z zs] //=; by rewrite -IH.
 Qed.
 
+(** TODO upstream to auto *)
 #[global] Instance refine_bs_app' (str a b : BS.t) :
   Refine1 true true (str ++ a = str ++ b)%bs [a = b].
-Proof. tac_refine. move: H. apply: inj. Qed.
-
-#[global] Arguments BS.append : simpl never.
+Proof. tac_refine. exact: inj (BS.append str). Qed.
 
 Section with_cpp.
   Context `{Σ : cpp_logic, σ : genv}.