Don't link in sanitizer runtimes if -nostdlib/-nodefaultlibs is provided.

It makes no sense to link in sanitizer runtimes in this case: the user
probably doesn't want to see any system/toolchain libs in his link if he
provides these flags, and the link will most likely fail anyway - as sanitizer
runtimes depend on libpthread, libdl, libc etc.

Also, see discussion in https://code.google.com/p/address-sanitizer/issues/detail?id=344

llvm-svn: 218541

clang/lib/Driver/Tools.cpp

@@ -2243,6 +2243,10 @@ collectSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
 // C runtime, etc). Returns true if sanitizer system deps need to be linked in.
 static bool addSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
                                  ArgStringList &CmdArgs) {
+  // Don't link in any sanitizer runtimes if we have no system libraries.
+  if (Args.hasArg(options::OPT_nostdlib) ||
+      Args.hasArg(options::OPT_nodefaultlibs))
+    return false;
   SmallVector<StringRef, 4> SharedRuntimes, StaticRuntimes,
       HelperStaticRuntimes;
   collectSanitizerRuntimes(TC, Args, SharedRuntimes, StaticRuntimes,

clang/test/Driver/sanitizer-ld.c

@@ -301,3 +301,10 @@
 // CHECK-LSAN-ASAN-LINUX-NOT: libclang_rt.lsan
 // CHECK-LSAN-ASAN-LINUX: libclang_rt.asan-x86_64
 // CHECK-LSAN-ASAN-LINUX-NOT: libclang_rt.lsan
+
+// RUN: %clang -nostdlib -fsanitize=address %s -### -o %t.o 2>&1 \
+// RUN:     -target x86_64-unknown-linux \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-NOSTDLIB %s
+// CHECK-NOSTDLIB: "{{.*}}ld{{(.exe)?}}"
+// CHECK-NOSTDLIB-NOT: libclang_rt.asan