[cfe-commits] r169328 - in /cfe/trunk: lib/Driver/Tools.cpp test/Driver/asan-ld.c

[Chandler Carruth]

On Wed, Dec 5, 2012 at 12:13 AM, Kostya Serebryany <kcc at google.com> wrote:

> +asan/tsan/msan folks
>
> That's not as simple as this, I afraid.
> In *san there are two different kinds of interceptors.
> 1. foo from libc/libstc++ is completely replaced with foo from asan.
> Example: malloc, operator new
> 2. foo from libc/libstc++ is wrapped, such that when a user calls foo it
> calls the asan copy, but then the asan function calls the original foo.
> Example: pthread_create, __cxa_throw
>
> This change allows to use -static-libstdc++ with asan w/o link failures,
> but asan is still broken for -static-libstdc++ in a subtle way (since the
> __cxa_throw is not intercepted, asan will have rare false positives in
> presence of exceptions).
>

Can you describe the rare false positive? What would be needed to fully fix
this?


> Tsan also intercepts __cxa_guard in the similar way, so it will have false
> positives on function scope statics.
>
> Do we really care that much about linking asan with static libstdc++?
>

In my opinion, yes. We already have too much that is special about linking
with asan....


>
> --kcc
>
>
> On Wed, Dec 5, 2012 at 2:54 AM, Chandler Carruth <chandlerc at gmail.com>wrote:
>
>> Author: chandlerc
>> Date: Tue Dec  4 16:54:37 2012
>> New Revision: 169328
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=169328&view=rev
>> Log:
>> Add -whole-archive around the ASan runtime archive in the link command.
>>
>> This ensures that even though it comes first, we pick up its .o files.
>> Note that if we can use this (or something similar / equivalent) on
>> other platforms, we could potentially remove
>> ReplaceOperatorsNewAndDelete from the ASan runtimes.
>>
>> We should probably do something similar for TSan and MSan as well.
>>
>> Modified:
>>     cfe/trunk/lib/Driver/Tools.cpp
>>     cfe/trunk/test/Driver/asan-ld.c
>>
>> Modified: cfe/trunk/lib/Driver/Tools.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=169328&r1=169327&r2=169328&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Driver/Tools.cpp (original)
>> +++ cfe/trunk/lib/Driver/Tools.cpp Tue Dec  4 16:54:37 2012
>> @@ -1524,8 +1524,14 @@
>>        // 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));
>> +      // strategy of inserting it at the front of the link command. It
>> also
>> +      // needs to be forced to end up in the executable, so wrap it in
>> +      // whole-archive.
>> +      SmallVector<const char*, 3> PrefixArgs;
>> +      PrefixArgs.push_back("-whole-archive");
>> +      PrefixArgs.push_back(Args.MakeArgString(LibAsan));
>> +      PrefixArgs.push_back("-no-whole-archive");
>> +      CmdArgs.insert(CmdArgs.begin(), PrefixArgs.begin(),
>> PrefixArgs.end());
>>        CmdArgs.push_back("-lpthread");
>>        CmdArgs.push_back("-ldl");
>>        CmdArgs.push_back("-export-dynamic");
>>
>> Modified: cfe/trunk/test/Driver/asan-ld.c
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/asan-ld.c?rev=169328&r1=169327&r2=169328&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Driver/asan-ld.c (original)
>> +++ cfe/trunk/test/Driver/asan-ld.c Tue Dec  4 16:54:37 2012
>> @@ -19,7 +19,7 @@
>>  //
>>  // CHECK-LINUX-CXX: "{{.*}}ld{{(.exe)?}}"
>>  // CHECK-LINUX-CXX-NOT: "-lc"
>> -// CHECK-LINUX-CXX: libclang_rt.asan-i386.a"
>> +// CHECK-LINUX-CXX: "-whole-archive" "{{.*}}libclang_rt.asan-i386.a"
>> "-no-whole-archive"
>>  // CHECK-LINUX-CXX: "-lpthread"
>>  // CHECK-LINUX-CXX: "-ldl"
>>  // CHECK-LINUX-CXX: "-export-dynamic"
>> @@ -32,7 +32,7 @@
>>  //
>>  // 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: "-whole-archive"
>> "{{.*}}libclang_rt.asan-i386.a" "-no-whole-archive"
>>  // CHECK-LINUX-CXX-STATIC: stdc++
>>
>>  // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
>>
>>
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