<div style="font-family: arial, helvetica, sans-serif; font-size: 10pt">Hi Matt,<div><br></div><div>This breaks building programs with ASan:<br>$ cat zzz.cc</div><div><div>int main(int argc, char *argv[]) {</div><div>  return 0;</div>
<div>}</div><div>$ clang++ -fsanitize=address zzz.cc</div><div><div>/tmp/zzz-YkVYcB.o: In function `main':</div><div>zzz.cc:(.text+0xfb): undefined reference to `__asan_report_store4'</div><div>zzz.cc:(.text+0x157): undefined reference to `__asan_report_store4'</div>
<div>zzz.cc:(.text+0x18b): undefined reference to `__asan_report_store8'</div><div>/tmp/zzz-YkVYcB.o: In function `asan.module_ctor':</div><div>zzz.cc:(.text+0x1f5): undefined reference to `__asan_init'</div><div>
clang-3: error: linker command failed with exit code 1 (use -v to see invocation)</div></div><div><br></div><br><div class="gmail_quote">On Tue, Dec 4, 2012 at 1:18 PM, Matt Beaumont-Gay <span dir="ltr"><<a href="mailto:matthewbg@google.com" target="_blank">matthewbg@google.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: matthewbg<br>
Date: Tue Dec  4 15:18:26 2012<br>
New Revision: <a href="tel:169310" value="+49169310">169310</a><br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=169310&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=169310&view=rev</a><br>
Log:<br>
Currently, with -fsanitize=address, the driver appends libclang_rt.asan.a to<br>
the link command. This all works fine when the driver is also responsible for<br>
adding -lstdc++ to the link command. But, if -lstdc++ (or libstdc++.a, etc) is<br>
passed explicitly to the driver, the ASan runtime will appear in the link<br>
command after the standard library, leading to multiple-definition errors for<br>
the global 'operator new' and 'operator delete'. Fix this in a painfully<br>
simple way, by inserting libclang_rt.asan.a at the start of the link command<br>
instead of the end.<br>
<br>
If we need to do something more clever, we can walk the link command looking<br>
for something that resembles libstdc++ and insert libclang_rt.asan.a as late<br>
as possible, but the simple solution works for now.<br>
<br>
Modified:<br>
    cfe/trunk/lib/Driver/Tools.cpp<br>
    cfe/trunk/test/Driver/asan-ld.c<br>
<br>
Modified: cfe/trunk/lib/Driver/Tools.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=169310&r1=169309&r2=169310&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=169310&r1=169309&r2=169310&view=diff</a><br>

==============================================================================<br>
--- cfe/trunk/lib/Driver/Tools.cpp (original)<br>
+++ cfe/trunk/lib/Driver/Tools.cpp Tue Dec  4 15:18:26 2012<br>
@@ -1512,7 +1512,7 @@<br>
     llvm::sys::path::append(LibAsan, "lib", "linux",<br>
         (Twine("libclang_rt.asan-") +<br>
             TC.getArchName() + "-android.so"));<br>
-    CmdArgs.push_back(Args.MakeArgString(LibAsan));<br>
+    CmdArgs.insert(CmdArgs.begin(), Args.MakeArgString(LibAsan));<br>
   } else {<br>
     if (!Args.hasArg(options::OPT_shared)) {<br>
       // LibAsan is "libclang_rt.asan-<ArchName>.a" in the Linux library<br>
@@ -1521,7 +1521,11 @@<br>
       llvm::sys::path::append(LibAsan, "lib", "linux",<br>
                               (Twine("libclang_rt.asan-") +<br>
                                TC.getArchName() + ".a"));<br>
-      CmdArgs.push_back(Args.MakeArgString(LibAsan));<br>
+      // The ASan runtime needs to come before -lstdc++ (or -lc++, libstdc++.a,<br>
+      // etc.) so that the linker picks ASan's versions of the global 'operator<br>
+      // new' and 'operator delete' symbols. We take the extreme (but simple)<br>
+      // strategy of inserting it at the front of the link command.<br>
+      CmdArgs.insert(CmdArgs.begin(), Args.MakeArgString(LibAsan));<br>
       CmdArgs.push_back("-lpthread");<br>
       CmdArgs.push_back("-ldl");<br>
       CmdArgs.push_back("-export-dynamic");<br>
<br>
Modified: cfe/trunk/test/Driver/asan-ld.c<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/asan-ld.c?rev=169310&r1=169309&r2=169310&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/asan-ld.c?rev=169310&r1=169309&r2=169310&view=diff</a><br>

==============================================================================<br>
--- cfe/trunk/test/Driver/asan-ld.c (original)<br>
+++ cfe/trunk/test/Driver/asan-ld.c Tue Dec  4 15:18:26 2012<br>
@@ -24,7 +24,17 @@<br>
 // CHECK-LINUX-CXX: "-ldl"<br>
 // CHECK-LINUX-CXX: "-export-dynamic"<br>
 // CHECK-LINUX-CXX: stdc++<br>
+<br>
+// RUN: %clang -no-canonical-prefixes %s -### -o /dev/null -fsanitize=address \<br>
+// RUN:     -target i386-unknown-linux --sysroot=%S/Inputs/basic_linux_tree \<br>
+// RUN:     -lstdc++ -static 2>&1 \<br>
+// RUN:   | FileCheck --check-prefix=CHECK-LINUX-CXX-STATIC %s<br>
 //<br>
+// CHECK-LINUX-CXX-STATIC: "{{.*}}ld{{(.exe)?}}"<br>
+// CHECK-LINUX-CXX-STATIC-NOT: stdc++<br>
+// CHECK-LINUX-CXX-STATIC: libclang_rt.asan-i386.a"<br>
+// CHECK-LINUX-CXX-STATIC: stdc++<br>
+<br>
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \<br>
 // RUN:     -target arm-linux-androideabi -fsanitize=address \<br>
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \<br>
<br>
<br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div>Alexey Samsonov, MSK</div><br>
</div></div>