Address some PR feedback

Author: alexcrichton

ci/docker/wasm32-unknown-wasi/Dockerfile

@@ -1,4 +1,7 @@
-FROM ubuntu:18.04 as reference-sysroot
+# In the first container we want to assemble the `wasi-sysroot` by compiling it
+# from source. This requires a clang 8.0+ compiler with enough wasm support and
+# then we're just running a standard `make` inside of what we clone.
+FROM ubuntu:18.04 as wasi-sysroot
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
@@ -14,15 +17,29 @@ RUN apt-get update && \
     ssh \
     xz-utils
 
+# Fetch clang 8.0+ which is used to compile the wasi target and link our
+# programs together.
 RUN curl http://releases.llvm.org/8.0.0/clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-18.04.tar.xz | tar xJf -
 RUN mv /clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-18.04 /wasmcc
 
-RUN git clone https://github.com/CraneStation/reference-sysroot-wasi && \
-  cd reference-sysroot-wasi && \
-  git reset --hard d5a609fe63926533e1054e539ba5f2693d51bdf5
-RUN make -C reference-sysroot-wasi install -j $(nproc) WASM_CC=/wasmcc/bin/clang INSTALL_DIR=/wasm-sysroot
-COPY docker/wasm32-unknown-wasi/clang.sh /wasm-sysroot/bin/clang
+# Note that we're using `git reset --hard` to pin to a specific commit for
+# verification for now. The sysroot is currently in somewhat of a state of flux
+# and is expected to have breaking changes, so this is an attempt to mitigate
+# those breaking changes on `libc`'s own CI
+RUN git clone https://github.com/CraneStation/wasi-sysroot && \
+  cd wasi-sysroot && \
+  git reset --hard 320054e84f8f2440def3b1c8700cedb8fd697bf8
+RUN make -C wasi-sysroot install -j $(nproc) WASM_CC=/wasmcc/bin/clang INSTALL_DIR=/wasi-sysroot
 
+# This is a small wrapper script which executes the actual clang binary in
+# `/wasmcc` and then is sure to pass the right `--sysroot` argument which we
+# just built above.
+COPY docker/wasm32-unknown-wasi/clang.sh /wasi-sysroot/bin/clang
+
+# In the second container we're going to build the `wasmtime` binary which is
+# used to execute wasi executables. This is a standard Rust project so we're
+# just checking out a known revision (which pairs with the sysroot one we
+# downlaoded above) and then we're building it with Cargo
 FROM ubuntu:18.04 as wasmtime
 
 RUN apt-get update && \
@@ -43,13 +60,12 @@ ENV PATH=/root/.cargo/bin:$PATH
 RUN apt-get install -y --no-install-recommends python
 RUN git clone https://github.com/CraneStation/wasmtime-wasi wasmtime && \
   cd wasmtime && \
-  git reset --hard a7ac05df74759a7536b2b1e30adc6ff4867e36c3
-
-# Install wasmtime in /usr/bin, but make sure to remove rust afterwards because
-# we don't want it conflicting with the main Rust we're using to compile
-# `libc`.
+  git reset --hard 4fe2d6084e5b5cc74e69a26860f12750df51d339
 RUN cargo build --release --manifest-path wasmtime/Cargo.toml
 
+# And finally in the last image we're going to assemble everything together.
+# We'll install things needed at runtime for now and then copy over the
+# sysroot/wasmtime artifacts into their final location.
 FROM ubuntu:18.04
 
 RUN apt-get update && \
@@ -58,12 +74,19 @@ RUN apt-get update && \
     libc6-dev \
     libxml2
 
+# Copy over clang we downloaded to link executables ...
 COPY --from=reference-sysroot /wasmcc /wasmcc/
-COPY --from=reference-sysroot /wasm-sysroot/ /wasm-sysroot/
+# ... and the sysroot we built to link executables against ...
+COPY --from=reference-sysroot /wasi-sysroot/ /wasi-sysroot/
+# ... and finally wasmtime to actually execute binaries
 COPY --from=wasmtime /wasmtime/target/release/wasmtime /usr/bin/
 
+# Of note here is our clang wrapper which just executes a normal clang
+# executable with the right sysroot, and then we're sure to turn off the
+# crt-static feature to ensure that the CRT that we're specifying with `clang`
+# is used.
 ENV CARGO_TARGET_WASM32_UNKNOWN_WASI_RUNNER=wasmtime \
-  CARGO_TARGET_WASM32_UNKNOWN_WASI_LINKER=/wasm-sysroot/bin/clang \
-  CC_wasm32_unknown_wasi=/wasm-sysroot/bin/clang \
+  CARGO_TARGET_WASM32_UNKNOWN_WASI_LINKER=/wasi-sysroot/bin/clang \
+  CC_wasm32_unknown_wasi=/wasi-sysroot/bin/clang \
   PATH=$PATH:/rust/bin \
   RUSTFLAGS=-Ctarget-feature=-crt-static

ci/docker/wasm32-unknown-wasi/clang.sh

@@ -1,2 +1,2 @@
-#!/bin/sh
-exec /wasmcc/bin/clang --target=wasm32-unknown-wasi --sysroot /wasm-sysroot "$@"
+#!/usr/bin/env sh
+exec /wasmcc/bin/clang --target=wasm32-unknown-wasi --sysroot /wasi-sysroot "$@"

libc-test/build.rs

@@ -1896,37 +1896,27 @@ fn test_wasi(target: &str) {
     cfg.type_name(move |ty, is_struct, is_union| match ty {
         "FILE" => ty.to_string(),
         t if is_union => format!("union {}", t),
-        t if t.starts_with("__wasi") && t.ends_with("_u") => format!("union {}", t),
+        t if t.starts_with("__wasi") && t.ends_with("_u") => {
+            format!("union {}", t)
+        }
         t if t.starts_with("__wasi") && is_struct => format!("struct {}", t),
         t if t.ends_with("_t") => t.to_string(),
         t if is_struct => format!("struct {}", t),
         t => t.to_string(),
     });
 
-    // This is an opaque struct but we go through shenanigans to define values
-    // for it
-    cfg.skip_struct(move |ty| ty == "__clockid");
-
     cfg.field_name(move |_struct, field| {
         match field {
-			// deal with fields as rust keywords
+            // deal with fields as rust keywords
             "type_" => "type".to_string(),
             s => s.to_string(),
         }
     });
 
-    cfg.skip_static(move |name| {
-        match name {
-            // wasi shenanigans for defining CLOCK_REALTIME and such
-            s if s.starts_with("__CLOCK") => true,
-            _ => false,
-        }
-    });
-
     // Looks like LLD doesn't merge duplicate imports, so if the Rust
     // code imports from a module and the C code also imports from a
     // module we end up with two imports of function pointers which
-    // improt the same thing bug have different function pointers
+    // import the same thing but have different function pointers
     cfg.skip_fn_ptrcheck(|f| f.starts_with("__wasi"));
 
     cfg.generate("../src/lib.rs", "main.rs");