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

[Alexey Samsonov]

On Fri, Jul 11, 2014 at 12:05 PM, Timur Iskhodzhanov <timurrrr at google.com>
wrote:

> On Windows, we currently have two RTLs -- the "full" one, linked to the
> app; and a mini dll_thunk one, delegating ASan interface calls to the main
> one.
>

Yes, I understand your goal, I have concerns about the way you reach it
(SANITIZER_DLL_THUNK, see comment about compile definitons in public
sanitizer_common headers).
If you need _some_ stuff from sanitizer_common headers for building your
special asan_dll_thunk.cc, it would probably be better to add

// Interceptors in dll thunk don't need interface attribute because ....
#undef SANITIZER_INTERFACE_ATTRIBUTE
#define SANITIZER_INTERFACE_ATTRIBUTE

to the .cc file


> The dllexport attribute should only be applied to interface functions
> exported by the full/main one.
>


> 11 июля 2014 г. 22:28 пользователь "Alexey Samsonov" <vonosmas at gmail.com>
> написал:
>
>
>> 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)
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>
>>
>>
>>
>> --
>> Alexey Samsonov
>> vonosmas at gmail.com
>>
>


-- 
Alexey Samsonov
vonosmas at gmail.com
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