Review comments

.github/workflows/main.yml

@@ -172,10 +172,10 @@ jobs:
       - run: cargo install wasm-component-ld@0.5.21
       - name: Install LLVM 22
         run: |
-          wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
           v=22
           rel=$(lsb_release -cs)
-          sudo apt-add-repository "deb http://apt.llvm.org/$rel/ llvm-toolchain-$rel-$v main"
+          wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/keyrings/llvm.asc
+          echo "deb [signed-by=/etc/apt/keyrings/llvm.asc] http://apt.llvm.org/$rel/ llvm-toolchain-$rel-$v main" | sudo tee /etc/apt/sources.list.d/llvm-$v.list
           sudo apt-get update -y && sudo apt-get install -y clang-$v lld-$v
       - run: |
           cmake -G Ninja -B build -S . \

CppExceptions.md

@@ -3,7 +3,7 @@
 > **Note**: this documentation does not cover wasi-sdk-31, the latest version
 > of wasi-sdk at this time.
 
-From wasi-sdk-32 and onwards the artifacts produced by this repository support
+From wasi-sdk-33 and onwards the artifacts produced by this repository support
 compiling C++ code both with and without exceptions. The sysroot for wasm
 targets contains two copies of the C++ standard library and headers -- one with
 exceptions enabled and one with exceptions disabled. These are automatically
@@ -62,9 +62,9 @@ wasi-sdk at this time:
   issues in this repository itself as well as [resolving some upstream
   issues](https://github.com/llvm/llvm-project/issues/188077).
 * Currently `-fwasm-exceptions` is a required flag to enable C++ exceptions.
-  It's unclear whethe `-fexceptions` should also be supported as a substitute.
+  It's unclear whether `-fexceptions` should also be supported as a substitute.
 * Currently LLVM defaults to using the legacy exception-handling proposal and
   this will likely change in the future. Precompiled libraries for wasi-sdk are
-  all built with the standard exception-handlign proposal.
+  all built with the standard exception-handling proposal.
 * Currently `-lunwind` is required when linking, but this may become automatic
   in the future.

cmake/wasi-sdk-sysroot.cmake

@@ -377,6 +377,12 @@ endfunction()
 function(define_libcxx target)
   add_custom_target(libcxx-${target})
 
+  # For dual-mode exceptions-and-not there are two versions of libcxx which are
+  # compiled and placed into the sysroot. They're named slightly differently to
+  # have unique CMake rules.
+  #
+  # Otherwise there's only one build of libcxx and it's either got exceptions for
+  # it doesn't depending on configuration.
   if (WASI_SDK_EXCEPTIONS STREQUAL "DUAL")
     define_libcxx_and_lto(${target} "" OFF)
     define_libcxx_and_lto(${target} "-exn" ON)