[llvm] r301007 - [libFuzzer] Changing thread_local to __thread in libFuzzer

[Kostya Serebryany via llvm-commits]

On Fri, Apr 21, 2017 at 11:46 AM, George Karpenkov <ekarpenkov at apple.com>
wrote:

> Hi Kostya,
>
> Additionally, on one of the windows buildbots libfuzzer compilation fails
> due to __builtin_bswapX not available.
>
I guess we are not compiling libFuzzer with clang there.


> Would it be a good idea to #ifdef around that and do a manual slower
> implementation otherwise?
>
That's fine, but every time we do such things there is a risk to lose
performance w/o noticing.
So, please double-check that the main use case actually keeps using the
proper intrinsic

>
> As for the thread_local replacement, I’ll look into that, seems easiest to
> only apply the replacement for older Apple machines.
>

ok


> I’m more surprised it worked in the first place, since IIRC C++11 standard
> does not allow redefining keywords.
>

But you only need to ifdef for the compilers that don't treat thread_local
is the keyword, right?


>
> George
>
> On Apr 21, 2017, at 11:22 AM, Kostya Serebryany <kcc at google.com> wrote:
>
> yes, see it. thanks!
>
> On Fri, Apr 21, 2017 at 11:22 AM, Kuba Mracek <mracek at apple.com> wrote:
>
>> We've reverted the patch that tries to build libFuzzer by default.
>>
>> We'll look into that.
>>
>> Kuba
>>
>> On 21 Apr 2017, at 11:17, Kostya Serebryany via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>> Breaks on windows.
>>
>> In file included from C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\yvals.h:7:
>> C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\xkeycheck.h(250,5):  error: The C++ Standard Library forbids macroizing keywords. Enable warning C4005 to find the forbidden macro.
>>    #error The C++ Standard Library forbids macroizing keywords. Enable warning C4005 to find the forbidden macro.
>>     ^
>>
>> http://lab.llvm.org:8011/builders/sanitizer-windows/builds/10026/steps/build%20LLVMFuzzer/logs/stdio
>>
>>
>> Why did the cmake check on windows decide to use the -D hack?
>>
>>
>>
>>
>> On Fri, Apr 21, 2017 at 10:39 AM, Kuba Mracek via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: kuba.brecka
>>> Date: Fri Apr 21 12:39:50 2017
>>> New Revision: 301007
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=301007&view=rev
>>> Log:
>>> [libFuzzer] Changing thread_local to __thread in libFuzzer
>>>
>>> Old Apple compilers do not support thread_local keyword. This patch adds
>>> -Dthread_local=__thread when the compiler doesn't support thread_local.
>>>
>>> Differential Revision: https://reviews.llvm.org/D32312
>>>
>>>
>>> Modified:
>>>     llvm/trunk/lib/Fuzzer/CMakeLists.txt
>>>
>>> Modified: llvm/trunk/lib/Fuzzer/CMakeLists.txt
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Fuzzer/CM
>>> akeLists.txt?rev=301007&r1=301006&r2=301007&view=diff
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Fuzzer/CMakeLists.txt (original)
>>> +++ llvm/trunk/lib/Fuzzer/CMakeLists.txt Fri Apr 21 12:39:50 2017
>>> @@ -1,3 +1,16 @@
>>> +include(CheckCXXSourceCompiles)
>>> +
>>> +CHECK_CXX_SOURCE_COMPILES("
>>> +    static thread_local int blah;
>>> +    int main() {
>>> +      return 0;
>>> +    }
>>> +    " HAS_THREAD_LOCAL)
>>> +
>>> +if( NOT HAS_THREAD_LOCAL )
>>> +    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Dthread_local=__thread")
>>> +endif()
>>> +
>>>  set(LIBFUZZER_FLAGS_BASE "${CMAKE_CXX_FLAGS}")
>>>  # Disable the coverage and sanitizer instrumentation for the fuzzer
>>> itself.
>>>  set(CMAKE_CXX_FLAGS "${LIBFUZZER_FLAGS_BASE}
>>> -fno-sanitize-coverage=trace-pc-guard,edge,trace-cmp,indirect-calls,8bit-counters
>>> -Werror")
>>>
>>>
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>>
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