[cfe-commits] [PATCH] Fix ordering of libclang_rt.asan.a and libstdc++

[Matt Beaumont-Gay]

Hi chandlerc,

Currently, with -fsanitize=address, the driver appends libclang_rt.asan.a to the link command. This all works fine when the driver is also responsible for adding -lstdc++ to the link command. But, if -lstdc++ (or libstdc++.a, etc) is passed explicitly to the driver, the ASan runtime will appear in the link command after the standard library, leading to multiple-definition errors for the global 'operator new' and 'operator delete'. Fix this in a painfully simple way, by inserting libclang_rt.asan.a at the start of the link command instead of the end.

http://llvm-reviews.chandlerc.com/D166

Files:
  lib/Driver/Tools.cpp
  test/Driver/asan-ld.c

Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1512,16 +1512,20 @@
     llvm::sys::path::append(LibAsan, "lib", "linux",
         (Twine("libclang_rt.asan-") +
             TC.getArchName() + "-android.so"));
-    CmdArgs.push_back(Args.MakeArgString(LibAsan));
+    CmdArgs.insert(CmdArgs.begin(), Args.MakeArgString(LibAsan));
   } else {
     if (!Args.hasArg(options::OPT_shared)) {
       // LibAsan is "libclang_rt.asan-<ArchName>.a" in the Linux library
       // resource directory.
       SmallString<128> LibAsan(TC.getDriver().ResourceDir);
       llvm::sys::path::append(LibAsan, "lib", "linux",
                               (Twine("libclang_rt.asan-") +
                                TC.getArchName() + ".a"));
-      CmdArgs.push_back(Args.MakeArgString(LibAsan));
+      // The ASan runtime needs to come before -lstdc++ (or -lc++, libstdc++.a,
+      // etc.) so that the linker picks ASan's versions of the global 'operator
+      // new' and 'operator delete' symbols. We take the extreme (but simple)
+      // strategy of inserting it at the front of the link command.
+      CmdArgs.insert(CmdArgs.begin(), Args.MakeArgString(LibAsan));
       CmdArgs.push_back("-lpthread");
       CmdArgs.push_back("-ldl");
       CmdArgs.push_back("-export-dynamic");
Index: test/Driver/asan-ld.c
===================================================================
--- test/Driver/asan-ld.c
+++ test/Driver/asan-ld.c
@@ -24,7 +24,17 @@
 // CHECK-LINUX-CXX: "-ldl"
 // CHECK-LINUX-CXX: "-export-dynamic"
 // CHECK-LINUX-CXX: stdc++
+
+// RUN: %clang -no-canonical-prefixes %s -### -o /dev/null -fsanitize=address \
+// RUN:     -target i386-unknown-linux --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:     -lstdc++ -static 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-LINUX-CXX-STATIC %s
 //
+// CHECK-LINUX-CXX-STATIC: "{{.*}}ld{{(.exe)?}}"
+// CHECK-LINUX-CXX-STATIC-NOT: stdc++
+// CHECK-LINUX-CXX-STATIC: libclang_rt.asan-i386.a"
+// CHECK-LINUX-CXX-STATIC: stdc++
+
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target arm-linux-androideabi -fsanitize=address \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D166.1.patch
Type: text/x-patch
Size: 2280 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20121204/98018bcf/attachment.bin>