[compiler-rt] r212815 - [ASan/Win] Don't apply dllexport to __asan_init in the DLL thunk

[Timur Iskhodzhanov]

Reid, Hans,

I have a hard time writing a simple LIT test that would fail before the fix.

Here's a small standalone repro:
---- f.cc ----
#if CONFIG==1
extern "C" __declspec(dllexport) int f1() {
  int x = 0;
  return 1;
}
#else
extern "C" __declspec(dllexport) int f2() {
  int x = 0;
  return 2;
}
#endif
--------------

I can repro the failure @r212814 invoking link.exe directly (similar
to what Chromium does):
$ clang-cl -fsanitize=address -DCONFIG=1 f.cc -c -Fo1.obj && clang-cl
-fsanitize=address -DCONFIG=2 f.cc -c -Fo2.obj
$ link /DLL 1.obj
%LLVM_BUILD%\lib\clang\3.5.0\lib\windows\clang_rt.asan_dll_thunk-i386.lib
&& \
   link /DLL 2.obj 1.lib
%LLVM_BUILD%\lib\clang\3.5.0\lib\windows\clang_rt.asan_dll_thunk-i386.lib
...
clang_rt.asan_dll_thunk-i386.lib(asan_dll_thunk.cc.obj) : error
LNK2005: ___asan_init_v4 already defined in 1.lib(1.dll)

OK, cool, now I want to get the same error without invoking link.exe
directly and without knowing the path to the RTL:
[using the 1.lib generated by the previous link.exe command]
$ clang-cl -fsanitize=address -LD -DCONFIG=2 f.cc 1.lib -Fe2.dll && echo OOPS
   Creating library 2.lib and object 2.exp
OOPS

?!?!

Adding -### reveals that clang-cl calls link.exe with the following
args at the end of the command line:
... "...\clang_rt.asan_dll_thunk-i386.lib" "blablabla.obj" "1.lib"
and link.exe seems to be sensitive to the order in which the RTL and
1.lib appear on the command line!   8)
$ link /nologo /DLL 2.obj
%LLVM_BUILD%\lib\clang\3.5.0\lib\windows\clang_rt.asan_dll_thunk-i386.lib
1.lib && echo OOPS
OOPS
$ link /nologo /DLL 2.obj 1.lib
%LLVM_BUILD%\lib\clang\3.5.0\lib\windows\clang_rt.asan_dll_thunk-i386.lib
clang_rt.asan_dll_thunk-i386.lib(asan_dll_thunk.cc.obj) : error
LNK2005: ___asan_init_v4 already defined in 1.lib(1.dll)

I was unable to pass the lib and the RTL in the order required to
repro the bug using clang-cl, as clang-cl overrides the order of stuff
I pass via "-link".
Any ideas?
Or maybe it's Chromium/GYP that's doing something wrong?

--
Tim

2014-07-11 17:46 GMT+04:00 Timur Iskhodzhanov <timurrrr at google.com>:
> Author: timurrrr
> Date: Fri Jul 11 08:46:05 2014
> New Revision: 212815
>
> URL: http://llvm.org/viewvc/llvm-project?rev=212815&view=rev
> Log:
> [ASan/Win] Don't apply dllexport to __asan_init in the DLL thunk
>
> This fixes '___asan_init_v4 already defined' errors when linking some of Chromium DLLs.
> Looks like one of the DLL is using a .lib produced while linking another DLL and it exploded after r212699.
> I'm trying to come up with a small testcase...
>
> Modified:
>     compiler-rt/trunk/lib/asan/CMakeLists.txt
>     compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h
>
> Modified: compiler-rt/trunk/lib/asan/CMakeLists.txt
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/CMakeLists.txt?rev=212815&r1=212814&r2=212815&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/asan/CMakeLists.txt (original)
> +++ compiler-rt/trunk/lib/asan/CMakeLists.txt Fri Jul 11 08:46:05 2014
> @@ -179,7 +179,7 @@ else()
>        add_compiler_rt_runtime(clang_rt.asan_dll_thunk-${arch} ${arch} STATIC
>          SOURCES asan_dll_thunk.cc
>                  $<TARGET_OBJECTS:RTInterception.${arch}>
> -        CFLAGS ${ASAN_CFLAGS} -DASAN_DLL_THUNK
> +        CFLAGS ${ASAN_CFLAGS} -DASAN_DLL_THUNK -DSANITIZER_DLL_THUNK
>          DEFS ${ASAN_COMMON_DEFINITIONS})
>        add_dependencies(asan clang_rt.asan_dll_thunk-${arch})
>      endif()
>
> Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h
> URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h?rev=212815&r1=212814&r2=212815&view=diff
> ==============================================================================
> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h (original)
> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_internal_defs.h Fri Jul 11 08:46:05 2014
> @@ -17,7 +17,11 @@
>
>  // Only use SANITIZER_*ATTRIBUTE* before the function return type!
>  #if SANITIZER_WINDOWS
> -# define SANITIZER_INTERFACE_ATTRIBUTE __declspec(dllexport)
> +# if defined(SANITIZER_DLL_THUNK)
> +#  define SANITIZER_INTERFACE_ATTRIBUTE
> +# else
> +#  define SANITIZER_INTERFACE_ATTRIBUTE __declspec(dllexport)
> +# endif
>  // FIXME find out what we need on Windows, if anything.
>  # define SANITIZER_WEAK_ATTRIBUTE
>  #elif defined(SANITIZER_GO)
>
>
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