From 3a4699a6de31738f1212b3a326af58fe39e22f85 Mon Sep 17 00:00:00 2001
From: Mikael Zayenz Lagerkvist <lagerkvist@gecode.dev>
Date: Tue, 7 Jul 2026 20:54:59 +0200
Subject: [PATCH] Fix empty vector argument array construction

---
 changelog.in                 | 11 +++++++++++
 gecode/kernel/data/array.hpp |  3 ++-
 test/array.cpp               | 28 ++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/changelog.in b/changelog.in
index 3b76bb1a95..da6b386fd8 100755
--- a/changelog.in
+++ b/changelog.in
@@ -83,6 +83,17 @@ Rank:   minor
 Fix MSVC compilation of matrix slice conversion operators by fully
 qualifying their dependent return types.
 
+[ENTRY]
+Module: kernel
+What:   bug
+Rank:   minor
+Issue:  205
+Thanks: intractabilis
+[DESCRIPTION]
+Fix construction of argument arrays from empty `std::vector` instances
+so zero-length copies do not take the address of a nonexistent first
+element.
+
 [ENTRY]
 Module: float
 What:   bug
diff --git a/gecode/kernel/data/array.hpp b/gecode/kernel/data/array.hpp
index ffae114704..3e53964ea0 100644
--- a/gecode/kernel/data/array.hpp
+++ b/gecode/kernel/data/array.hpp
@@ -1557,7 +1557,8 @@ namespace Gecode {
   ArgArrayBase<T>::ArgArrayBase(const std::vector<T>& aa)
     : n(static_cast<int>(aa.size())),
       capacity(n < onstack_size ? onstack_size : n), a(allocate(n)) {
-    heap.copy<T>(a,&aa[0],n);
+    if (n > 0)
+      heap.copy<T>(a,aa.data(),n);
   }
 
   template<class T>
diff --git a/test/array.cpp b/test/array.cpp
index 1f0a3433a0..74fefb4dd2 100644
--- a/test/array.cpp
+++ b/test/array.cpp
@@ -34,6 +34,8 @@
 #include <gecode/kernel.hh>
 #include <gecode/int.hh>
 
+#include <vector>
+
 #include "test/test.hh"
 
 /// Check the test result and handle failed test
@@ -190,6 +192,32 @@ namespace Test {
     }
   };
 
+  /// Test name prefix for vector construction
+  static const std::string vectorPrefix("Array::Vector::");
+
+  /// %Class for testing construction from empty vectors
+  class EmptyVector : public Test::Base {
+  public:
+    /// Initialize test
+    EmptyVector(void) : Test::Base(vectorPrefix + "Empty") {}
+    /// Perform actual tests
+    bool run(void) {
+      std::vector<int> ints;
+      Gecode::IntArgs ia(ints);
+      if (ia.size() != 0)
+        return false;
+
+      std::vector<Gecode::IntVar> intVars;
+      Gecode::IntVarArgs iva(intVars);
+      if (iva.size() != 0)
+        return false;
+
+      std::vector<Gecode::BoolVar> boolVars;
+      Gecode::BoolVarArgs bva(boolVars);
+      return bva.size() == 0;
+    }
+  } emptyVectorTest;
+
   /// %Class for testing the VarArray iterator
   class VarArrayIterator : public Iterator {
   protected: