[clang] [memprof] Export __memprof_default_options_str on Darwin (PR #128920)

[Ellis Hoag via cfe-commits]

https://github.com/ellishg created https://github.com/llvm/llvm-project/pull/128920

The `-memprof-runtime-default-options` LLVM flag introduced in https://github.com/llvm/llvm-project/pull/118874 creates the `__memprof_default_options_str` symbol with `WeakAnyLinkage` on Darwin.

https://github.com/ellishg/llvm-project/blob/fa0202169af23419c4bcbf66eabd1beb6b6e8e34/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp#L573-L576

This ensures Darwin passes `-exported_symbol ___memprof_default_options_str` to the linker so that the runtime library has visibility into this symbol.

This will replace the earlier PR https://github.com/llvm/llvm-project/pull/128615

>From 2e1946730f7ae2473a4fc94f8918eb3d9d225d17 Mon Sep 17 00:00:00 2001
From: Ellis Hoag <ellishoag at meta.com>
Date: Wed, 26 Feb 2025 09:48:46 -0800
Subject: [PATCH] [memprof] Export __memprof_default_options_str on Darwin

---
 clang/lib/Driver/ToolChains/Darwin.cpp | 4 ++++
 clang/test/Driver/fmemprof.cpp         | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 75f126965e0ac..a2aeef4c4c475 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1617,6 +1617,10 @@ void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
     }
   }
 
+  if (Sanitize.needsMemProfRt())
+    if (hasExportSymbolDirective(Args))
+      addExportedSymbol(CmdArgs, "___memprof_default_options_str");
+
   const XRayArgs &XRay = getXRayArgs();
   if (XRay.needsXRayRt()) {
     AddLinkRuntimeLib(Args, CmdArgs, "xray");
diff --git a/clang/test/Driver/fmemprof.cpp b/clang/test/Driver/fmemprof.cpp
index 5165c4452fd57..b464320e58a94 100644
--- a/clang/test/Driver/fmemprof.cpp
+++ b/clang/test/Driver/fmemprof.cpp
@@ -17,3 +17,11 @@
 
 // RUN: not %clangxx --target=x86_64-linux-gnu -fprofile-generate -fmemory-profile-use=foo %s -### 2>&1 | FileCheck %s --check-prefix=CONFLICTWITHPGOINSTR
 // CONFLICTWITHPGOINSTR: error: invalid argument '-fmemory-profile-use=foo' not allowed with '-fprofile-generate'
+
+// Test that we export the __memprof_default_options_str on Darwin because it has WeakAnyLinkage
+// RUN: %clangxx --target=arm64-apple-ios -fmemory-profile %s -### 2>&1 | FileCheck %s -check-prefix=EXPORT-BASE --implicit-check-not=exported_symbol
+// RUN: %clangxx --target=x86_64-linux-gnu -fmemory-profile %s -### 2>&1 | FileCheck %s -check-prefix=EXPORT-BASE --implicit-check-not=exported_symbol
+// RUN: %clangxx --target=arm64-apple-ios -fmemory-profile -exported_symbols_list /dev/null %s -### 2>&1 | FileCheck %s --check-prefixes=EXPORT-BASE,EXPORT
+// FIXME: Darwin needs to link in the runtime, then we can use the regular CHECK prefix
+// EXPORT-BASE: "-cc1" {{.*}} "-fmemory-profile"
+// EXPORT: "-exported_symbol" "___memprof_default_options_str"