[clang] [clang] force libc linked with --no-as-needed when using compiler-rt (PR #95848)

[via cfe-commits]

https://github.com/ziyao233 created https://github.com/llvm/llvm-project/pull/95848

crtbegin.o in compiler-rt contains weak reference to __cxa_finalize, which is implemented in libc. When building a shared library with --as-needed option, libc may be incorrectly marked as inactive, resulting in unresolved symbols in crtbegin.o

This commit forces libc is linked with --no-as-needed option when using compiler-rt, fixing the problem.

>From 515e09198c6d9da95df3357552cb7b41b03b6e8c Mon Sep 17 00:00:00 2001
From: Yao Zi <ziyao at disroot.org>
Date: Mon, 17 Jun 2024 19:49:24 +0000
Subject: [PATCH] [clang] force libc linked with --no-as-needed when using
 compiler-rt

crtbegin.o in compiler-rt contains weak reference to __cxa_finalize,
which is implemented in libc. When building a shared library with
--as-needed option, libc may be incorrectly marked as inactive,
resulting in unresolved symbols in crtbegin.o

This commit forces libc is linked with --no-as-needed option when using
compiler-rt, fixing the problem.

Signed-off-by: Yao Zi <ziyao at disroot.org>
---
 clang/lib/Driver/ToolChains/Gnu.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index dedbfac6cb25d..419c6b6e43664 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -378,6 +378,7 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   const bool HasCRTBeginEndFiles =
       ToolChain.getTriple().hasEnvironment() ||
       (ToolChain.getTriple().getVendor() != llvm::Triple::MipsTechnologies);
+  const ToolChain::RuntimeLibType RLTType = ToolChain.GetRuntimeLibType(Args);
 
   ArgStringList CmdArgs;
 
@@ -625,8 +626,15 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       if (Args.hasArg(options::OPT_fsplit_stack))
         CmdArgs.push_back("--wrap=pthread_create");
 
-      if (!Args.hasArg(options::OPT_nolibc))
+      if (!Args.hasArg(options::OPT_nolibc)) {
+        if (RLTType == ToolChain::RLT_CompilerRT) {  
+          CmdArgs.push_back("--push-state");
+          CmdArgs.push_back("--no-as-needed");
+        }
         CmdArgs.push_back("-lc");
+        if (RLTType == ToolChain::RLT_CompilerRT)
+          CmdArgs.push_back("--pop-state");
+      }
 
       // Add IAMCU specific libs, if needed.
       if (IsIAMCU)