[clang] Don't pass sanitizers' rtlibs to linker with `-r` (PR #147905)

[Dmitry Chestnykh via cfe-commits]

https://github.com/chestnykh created https://github.com/llvm/llvm-project/pull/147905

If clang is invoked with `-r` (relocatable linking) then we shouldn't construct sanitizer arguments and then pass sanitizer runtime libs to the linker
GCC simply ignores `-fsanitize=...` if `-r` is also here

>From 8d1f86a9030fcc1184603309c6528190735a6fbc Mon Sep 17 00:00:00 2001
From: Dmitry Chestnykh <dm.chestnykh at gmail.com>
Date: Thu, 10 Jul 2025 10:19:31 +0300
Subject: [PATCH] Don't pass sanitizers' rtlibs to linker with `-r`

If clang is invoked with `-r` (relocatable linking)
then we shouldn't construct sanitizer arguments and
then pass sanitizer runtime libs to the linker
GCC simply ignores `-fsanitize=...` if `-r` is also here
---
 clang/lib/Driver/SanitizerArgs.cpp |  4 ++++
 clang/test/Driver/sanitizer-ld.c   | 16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 4bd61c2f8deef..037d98e4cfc3d 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -406,6 +406,10 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   SanitizerMask DiagnosedKinds; // All Kinds we have diagnosed up to now.
                                 // Used to deduplicate diagnostics.
   SanitizerMask Kinds;
+
+  if (Args.hasArg(options::OPT_r))
+    return;
+
   const SanitizerMask Supported = setGroupBits(TC.getSupportedSanitizers());
 
   CfiCrossDso = Args.hasFlag(options::OPT_fsanitize_cfi_cross_dso,
diff --git a/clang/test/Driver/sanitizer-ld.c b/clang/test/Driver/sanitizer-ld.c
index d2e4877e89d78..5144dbc2007d3 100644
--- a/clang/test/Driver/sanitizer-ld.c
+++ b/clang/test/Driver/sanitizer-ld.c
@@ -1369,3 +1369,19 @@
 // CHECK-DSO-SHARED-HWASAN-AARCH64-LINUX-NOT: "-lresolv"
 // CHECK-DSO-SHARED-HWASAN-AARCH64-LINUX-NOT: "--export-dynamic"
 // CHECK-DSO-SHARED-HWASAN-AARCH64-LINUX-NOT: "--dynamic-list"
+
+// RUN: %clang -fsanitize=address,undefined -r -### %s 2>&1 \
+// RUN:     --target=x86_64-unknown-linux -fuse-ld=ld \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | %{filecheck} --check-prefix=CHECK-RELOCATABLE-LINK-ASAN-UBSAN-RTLIB
+//
+// CHECK-RELOCATABLE-LINK-ASAN-UBSAN-RTLIB-NOT: "{{.*}}(asan|ubsan){{.*}}"
+
+// RUN: %clang -fsanitize=thread -r -### %s 2>&1 \
+// RUN:     --target=x86_64-unknown-linux -fuse-ld=ld \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | %{filecheck} --check-prefix=CHECK-RELOCATABLE-LINK-TSAN-RTLIB
+//
+// CHECK-RELOCATABLE-LINK-TSAN-RTLIB-NOT: "{{.*}}tsan{{.*}}"