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

[Alexey Samsonov]

On Fri, Jul 11, 2014 at 6:46 AM, Timur Iskhodzhanov <timurrrr at google.com>
wrote:

> 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
>

I find this very confusing. sanitizer_common is not a header-only library,
it's compiled once, and then the same object
files are put inside all sanitizer runtimes (ASan, TSan, MSan). But ASan
runtime #includes headers from sanitizer_common.
If you build some parts of ASan runtime with "-DSANITIZER_FOO=1" and build
sanitizer_common itself with "-DSANITIZER_FOO=0"
you may get all sorts of weird bugs. So I kind of advocate against
"SANITIZER_FOO" macro which are exposed in sanitizer_common headers.

Is it possible to find other solution? What SANITIZER_INTERFACE_ATTRIBUTE
are you trying to get rid of?



>  // FIXME find out what we need on Windows, if anything.
>  # define SANITIZER_WEAK_ATTRIBUTE
>  #elif defined(SANITIZER_GO)
>
>
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-- 
Alexey Samsonov
vonosmas at gmail.com
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