[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header by ndrewh · Pull Request #182943 · llvm/llvm-project

ndrewh · 2026-02-23T21:41:08Z

There is an issue on recent macOS versions with GetDyldImageHeaderViaSharedCache, which is fixed by adopting _dyld_get_dyld_header. We weakly declare this to ensure runtimes compile with older SDK (currently on CI bots).

rdar://167854578

llvmbot · 2026-02-23T21:42:09Z

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Andrew Haberlandt (ndrewh)

Changes

There is an issue on recent macOS versions with GetDyldImageHeaderViaSharedCache, which is fixed by adopting _dyld_get_dyld_header. We weakly declare this to ensure runtimes work on older OS, and also newer OS compiled with older SDK (i.e. the current bots).

rdar://167854578

Full diff: https://github.com/llvm/llvm-project/pull/182943.diff

3 Files Affected:

(modified) compiler-rt/lib/sanitizer_common/sanitizer_procmaps_mac.cpp (+6-2)
(modified) compiler-rt/lib/sanitizer_common/weak_symbols.txt (+1)
(modified) compiler-rt/lib/tsan/go/buildgo.sh (+1-1)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_procmaps_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_procmaps_mac.cpp
index 979729f15aa16..0e80f2e3916b2 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_procmaps_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_procmaps_mac.cpp
@@ -176,7 +176,7 @@ void MemoryMappingLayout::Reset() {
 // The dyld load address should be unchanged throughout process execution,
 // and it is expensive to compute once many libraries have been loaded,
 // so cache it here and do not reset.
-static mach_header *dyld_hdr = 0;
+static const mach_header *dyld_hdr = 0;
 static const char kDyldPath[] = "/usr/lib/dyld";
 static const int kDyldImageIdx = -1;
 
@@ -244,14 +244,18 @@ extern intptr_t _dyld_get_image_slide(const struct mach_header* mh);
 extern int dyld_shared_cache_iterate_text(
     const uuid_t cacheUuid,
     void (^callback)(const dyld_shared_cache_dylib_text_info *info));
+SANITIZER_WEAK_IMPORT const struct mach_header *_dyld_get_dyld_header(void);
 }  // extern "C"
 
-static mach_header *GetDyldImageHeaderViaSharedCache() {
+static const mach_header *GetDyldImageHeaderViaSharedCache() {
   uuid_t uuid;
   bool hasCache = _dyld_get_shared_cache_uuid(uuid);
   if (!hasCache)
     return nullptr;
 
+  if (&_dyld_get_dyld_header != nullptr)
+    return _dyld_get_dyld_header();
+
   size_t cacheLength;
   __block uptr cacheStart = (uptr)_dyld_get_shared_cache_range(&cacheLength);
   CHECK(cacheStart && cacheLength);
diff --git a/compiler-rt/lib/sanitizer_common/weak_symbols.txt b/compiler-rt/lib/sanitizer_common/weak_symbols.txt
index 77e7b5d9f702e..600ab8a7c649c 100644
--- a/compiler-rt/lib/sanitizer_common/weak_symbols.txt
+++ b/compiler-rt/lib/sanitizer_common/weak_symbols.txt
@@ -10,3 +10,4 @@ ___sanitizer_symbolize_demangle
 ___sanitizer_symbolize_flush
 ___sanitizer_symbolize_set_demangle
 ___sanitizer_symbolize_set_inline_frames
+__dyld_get_dyld_header
diff --git a/compiler-rt/lib/tsan/go/buildgo.sh b/compiler-rt/lib/tsan/go/buildgo.sh
index d9e56402ad48f..1340071819fcb 100755
--- a/compiler-rt/lib/tsan/go/buildgo.sh
+++ b/compiler-rt/lib/tsan/go/buildgo.sh
@@ -165,7 +165,7 @@ elif [ "$GOOS" = "netbsd" ]; then
 	"
 elif [ "$GOOS" = "darwin" ]; then
 	OSCFLAGS="-fPIC -Wno-unused-const-variable -Wno-unknown-warning-option -mmacosx-version-min=10.7"
-	OSLDFLAGS="-lpthread -fPIC -fpie -mmacosx-version-min=10.7"
+	OSLDFLAGS="-lpthread -fPIC -fpie -mmacosx-version-min=10.7 -Wl,-U,__dyld_get_dyld_header"
 	SRCS="
 		$SRCS
 		../rtl/tsan_platform_mac.cpp

github-actions · 2026-02-23T21:43:28Z

✅ With the latest revision this PR passed the C/C++ code formatter.

ndrewh · 2026-02-23T21:45:11Z

Fixed clang-format

With llvm/llvm-project#182943, the race detector syso has a weak import of __dyld_get_dyld_header, which is only defined on newer macOS (26.4+). For external linking with a pre-Xcode 26.4 C toolchain, we need to tell the C linker to permit that symbol not being defined. Pass a flag to do so. Change-Id: I95a3cd2c7fd3ad50bc47985b3ecca0d4e8352162 Reviewed-on: https://go-review.googlesource.com/c/go/+/755261 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Lasse Folger <lassefolger@google.com>

ndrewh · 2026-03-27T06:11:12Z

/cherry-pick 2e7d07a

ndrewh · 2026-03-27T06:11:49Z

I think we should cherry-pick this to make sure that clang 22 supports ASAN on macOS 26.4.

llvmbot · 2026-03-27T06:18:02Z

/cherry-pick 2e7d07a

Error: Command failed due to missing milestone.

ndrewh · 2026-03-27T06:23:02Z

/cherry-pick 2e7d07a

llvmbot · 2026-03-27T06:30:00Z

/pull-request #188913

@rpath

…t mode DirectBuild: deps simple enough to list files compile as first-class ninja edges instead of a cmake sub-process. tinycc converted — drops the overlay CMakeLists.txt and the recurring ASAN workarounds on the c2str host tool, which now gets -fno-sanitize=all unconditionally. ASAN dyld shim: macOS 26.4's Dyld.framework reimplemented dyld_shared_cache_iterate_text in Swift with a _Block_copy that deadlocks ASAN init (llvm/llvm-project#182943). Shim interposes a non-allocating version using _dyld_get_dyld_header. Linked via LC_LOAD_DYLIB + @rpath so it auto-loads with bun-debug — no env var. Darwin+ASAN only. workarounds.ts: self-obsoleting registry. Every temporary fix registers an expectedToBeFixed predicate; configure fails with cleanup instructions once the upstream fix ships. build.ts: quiet build output when exec args present (original bd behavior), `--` separator for flag disambiguation, `--target` accepts space-separated value, colored target name in done message, signal exit re-raised. Arg routing documented in file header. tty.ts: centralized ANSI/TTY abstraction. nameColor() hashes names to stable colors; stream.ts and the done message share it. config.ts/tools.ts: clangVersion captured from the existing toolchain-resolve --version spawn, exposed on Config. findTool returns {path, version}. Also: - configure() no longer prints; build.ts decides based on quiet mode - provides.sources deps get phonies pointing at compiled .o files - scripts/bd, scripts/bd.ps1 removed (bd is a package.json script) - scripts/build/CLAUDE.md: architecture doc with goals, ninja primer, common tasks, arg routing

(cherry picked from commit 2e7d07a)

past the ASAN runtime fix (llvm/llvm-project#191039). MODULAR_ORIG_COMMIT_REV_ID: 1773da5eabdc1456e1fac443ccf0aac439c6a895

…macOS (#34508) ## Problem `bun bd` aborts at startup on macOS releases older than 26.4 (seen on 15.6.1, Homebrew llvm@21): ``` AddressSanitizer: CHECK failed: sanitizer_procmaps_mac.cpp:214 "((res)) == ((0))" (0xffffffffffffffff, 0x0) <empty stack> Abort trap: 6 ``` The post-link `bun-debug --revision` smoke test dies with this, so the debug build never completes. Workaround has been `bun run build --asan=off`. ## Cause `scripts/build/shims/asan-dyld-shim.c` interposes `dyld_shared_cache_iterate_text` to keep ASAN init from deadlocking on macOS 26.4 (llvm/llvm-project#182943). It looks up the private `_dyld_get_dyld_header` via `dlsym` to synthesize the one cache entry ASAN needs. Apple's own `dyld_priv.h` marks that symbol ["Added in macOS/iOS 26.4"](https://github.com/apple-oss-distributions/dyld/blob/dyld-1376.6/include/mach-o/dyld_priv.h) (first appears in dyld-1376.6; absent from dyld-1340 and every earlier tag). On any macOS < 26.4, `dlsym` returns `NULL`, the shim returns `-1`, and compiler-rt's `CHECK_EQ(res, 0)` aborts. The shim is linked into every `cfg.darwin && cfg.asan` build with no runtime check, so it breaks every debug build on macOS hosts that predate 26.4. ## Fix When the shim can't synthesize the entry (`dlsym` returned `NULL`, or no shared cache), delegate to the real `dyld_shared_cache_iterate_text` instead of returning `-1`. The deadlock and the getter were introduced together in 26.4, so "getter absent" is exactly "real iterate is safe". This is the same shape as the upstream compiler-rt fix (llvm/llvm-project#188913): weak-import `_dyld_get_dyld_header`, use it when present, otherwise fall through to the existing iterate path. Calling the original by name from inside the interposer does not recurse. dyld explicitly adds an identity-mapping tuple for the defining image; from [DyldRuntimeState.cpp](https://github.com/apple-oss-distributions/dyld/blob/dyld-1378/dyld/DyldRuntimeState.cpp): > `// now add specific interpose so that the generic is not applied to the interposing dylib, so it can call through to old impl` (This is also how Apple's own `DYLD_INTERPOSE` wrapper example in [dyld-interposing.h](https://github.com/apple-oss-distributions/dyld/blob/main/include/mach-o/dyld-interposing.h) works.) ## Verification Shim is only compiled for `darwin && asan` (no CI lane exists for that combination); verified the change compiles clean with `-Wall -Wextra -fblocks` against stubbed darwin headers. Behaviour on 26.4+ is unchanged: `dlsym` finds the symbol there and the same synthesize path runs as before. ## Why this is the right fix The alternative is gating shim emission on host macOS version in `shims.ts`, but the runtime check is strictly better: one binary works on both, and it matches upstream exactly. The shim is temporary regardless (self-obsoletes via `workarounds.ts` once LLVM 22.1.4+ is the floor; #34299 deletes it as part of the LLVM 22 bump), so the goal here is just to stop breaking pre-26.4 macOS until that lands.  --- **no test proof** · iteration 0 · build/CI scripts only; test-proof not applicable

Fixes #826. ## Summary Wire rules_cc's stock `lsan` feature into the same augmentation path as asan, ubsan, and tsan: - add `//toolchain/config:use_lsan` and include it in `use_common_sanitizer` - add the Darwin `libclang_rt.lsan_osx_dynamic.dylib` filegroup and route it through `dynamic_runtime_lib` - add an end-to-end `//:lsan_test` and run it with the Linux sanitizer tests - add a focused macOS CI job using LLVM 22.1.8 The Darwin version pin is deliberate. On current macOS, LLVM 19.1.7, 20.1.8, and 21.1.8 all run `main` and then deadlock during LSan's exit check. The leak-check thread calls `dyld_shared_cache_iterate_text`, which lazily loads dyld introspection code and allocates while LSan holds its allocator lock. LLVM compiler-rt #182943 switched this path to `_dyld_get_dyld_header`; that fix was backported to LLVM 22, and LLVM 22.1.8 exits normally. The configured action graph now contains a `SolibSymlink` whose declared input is `libclang_rt.lsan_osx_dynamic.dylib`, so the runtime is provisioned rather than merely found incidentally in the local execroot. ## Verification On macOS arm64: - LLVM 19.1.7: times out after completing `main` - LLVM 20.1.8: times out after completing `main` - LLVM 21.1.8: times out after completing `main` - LLVM 22.1.8: `//:lsan_test` passes - `//:sanitizer_combo_flags_test` passes - `actionlint` and `git diff --check` pass Upstream fix: llvm/llvm-project#182943

ndrewh requested a review from DanBlackwell February 23, 2026 21:41

llvmbot added compiler-rt compiler-rt:tsan Thread sanitizer compiler-rt:sanitizer labels Feb 23, 2026

[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header

bdf57bf

ndrewh force-pushed the GetDyldImageHeaderViaSharedCache branch from ea41f5f to bdf57bf Compare February 23, 2026 21:44

DanBlackwell approved these changes Feb 23, 2026

View reviewed changes

ndrewh merged commit 2e7d07a into llvm:main Feb 24, 2026
10 checks passed

ndrewh mentioned this pull request Feb 24, 2026

[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header swiftlang/llvm-project#12431

Merged

ndrewh added this to the LLVM 22.x Release milestone Mar 27, 2026

github-project-automation Bot added this to LLVM Release Status Mar 27, 2026

github-project-automation Bot moved this to Needs Triage in LLVM Release Status Mar 27, 2026

github-project-automation Bot moved this from Needs Triage to Done in LLVM Release Status Mar 27, 2026

c-rhodes pushed a commit to llvmbot/llvm-project that referenced this pull request Mar 31, 2026

[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header (llvm#182943)

7b6514c

(cherry picked from commit 2e7d07a)

ndrewh referenced this pull request in modular/modular Apr 12, 2026

[KGEN] Skip ASAN lit tests on macOS 26 until the toolchain is bumped

49dafb0

past the ASAN runtime fix (llvm/llvm-project#191039). MODULAR_ORIG_COMMIT_REV_ID: 1773da5eabdc1456e1fac443ccf0aac439c6a895

robobun mentioned this pull request Jul 17, 2026

build(darwin): asan-dyld-shim falls through to real iterate on older macOS oven-sh/bun#34508

Merged

helly25 mentioned this pull request Aug 16, 2026

Wire up LeakSanitizer support bazel-contrib/toolchains_llvm#828

Merged

morningman mentioned this pull request Sep 29, 2026

[fix](build) Move the macOS toolchain to LLVM 22 so ASAN works on macOS 26.4+ apache/doris#68595

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[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header - #182943

[sanitizer_common] [Darwin] Adopt _dyld_get_dyld_header#182943
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