Test with LLVM 22 in CI, fix a setjmp/longjmp issue (WebAssembly#772)

This commit adds a new CI builder for LLVM 22, distinct from preexisting
builders using LLVM 20. This notably exposes a bug where setjmp/longjmp
needed a fix because the method of definition of `__c_setjmp`, the tag
used, changed in LLVM 22.

> **Note**: this is temporarily built on
WebAssembly#770 and
WebAssembly#771

Author: alexcrichton

.github/actions/setup/action.yml

@@ -51,15 +51,22 @@ runs:
         echo "NM=$CLANG_DIR/llvm-nm" >> $GITHUB_ENV
       if: runner.os == 'macOS'
 
-    # Note that this uses apt-based packages for installing Clang/tools to
-    # ensure that all various dependencies are also installed. Binaries from
-    # llvm-project depend on libtinfo.so and TBH I don't know what that is.
-    # Using apt-get should basically serve the same purpose though.
+    # Use apt repositories to install various clang versions on Linux as those
+    # generally work the best and are more available than per-release downloads
+    # of LLVM. Note that apt.llvm.org may be used for new enough versions of
+    # clang which aren't in Ubuntu 24.04.
     - name: Install LLVM tools (Linux)
       shell: bash
       run: |
         set -ex
         v=${{ inputs.clang_version }}
+        # For LLVM versions 21+ install from apt.llvm.org because the ubuntu
+        # 24.04 repositories don't have these binaries.
+        if [ $v -ge 21 ]; then
+          wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+          rel=$(lsb_release -cs)
+          sudo apt-add-repository "deb http://apt.llvm.org/$rel/ llvm-toolchain-$rel-$v main"
+        fi
         sudo apt-get update
         sudo apt-get install -y clang-$v clang-tools-$v lld-$v
         echo "CC=clang-$v" >> $GITHUB_ENV

.github/workflows/main.yml

@@ -162,6 +162,11 @@ jobs:
             test: true
             args: -DTARGET_TRIPLE=wasm32-wasip2
 
+          - name: Test LLVM 22
+            os: ubuntu-24.04
+            clang_version: 22
+            test: true
+            args: -DTARGET_TRIPLE=wasm32-wasip2
     steps:
     - uses: actions/checkout@v6
       with:

cmake/scripts/run-check-symbols.cmake

@@ -78,6 +78,7 @@ foreach(symbol IN LISTS final_undefined_symbols)
   if(NOT symbol MATCHES "^__mul" AND
      NOT symbol STREQUAL "__memory_base" AND
      NOT symbol STREQUAL "__indirect_function_table" AND
+     NOT symbol STREQUAL "__wasm_first_page_end" AND
      NOT symbol STREQUAL "__tls_base")
     file(APPEND ${out_undefined_symbols} "${symbol}\n")
   endif()

libc-top-half/musl/src/setjmp/wasm32/rt.c

@@ -81,3 +81,21 @@ __wasm_longjmp(void *env, int val)
         arg->val = val;
         __builtin_wasm_throw(1, arg); /* 1 == C_LONGJMP */
 }
+
+// The `__builtin_wasm_throw` invocation above will reference this symbol which
+// refers to a WebAssembly tag. The tag can't be defined in C but we can define
+// it with inline assembly, so do so here.
+//
+// Note that the means of defining this symbol changed historically, so this
+// is only done on LLVM 22+ where it's required.
+#if __clang_major__ >= 22
+__asm__(".globl __c_longjmp\n"
+#if defined(__wasm32__)
+        ".tagtype __c_longjmp i32\n"
+#elif defined(__wasm64__)
+        ".tagtype __c_longjmp i64\n"
+#else
+#error "Unsupported Wasm architecture"
+#endif
+        "__c_longjmp:\n");
+#endif