[FFmpeg-devel] [PATCH 1/3] configure: use c++11 and fallback to c++0x for c++ files

Marton Balint cus at passwd.hu
Sun Mar 26 13:22:35 EEST 2017


On Sat, 25 Mar 2017, James Almer wrote:

> On 3/25/2017 8:51 PM, Marton Balint wrote:
>> Needed for the C+11 atomics. Also change add_cxxflags to check_cxxflags.
>> 
>> Signed-off-by: Marton Balint <cus at passwd.hu>
>> ---
>>  configure | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/configure b/configure
>> index c1aeb6e..6823894 100755
>> --- a/configure
>> +++ b/configure
>> @@ -4648,7 +4648,7 @@ fi
>>
>>  add_cppflags -D_ISOC99_SOURCE
>>  add_cxxflags -D__STDC_CONSTANT_MACROS
>> -add_cxxflags -std=c++98
>> +check_cxxflags -std=c++11 || check_cxxflags -std=c++0x
>
> Do compilers that support setting --std=c++0x (Old provisional name for C++11)
> have actual support for std::atomic? They have by definition experimental and
> incomplete support for the standard in question.

Yes, gcc supports it since 4.4.
https://gcc.gnu.org/projects/cxx-status.html

Also MSVC 2012 (which AFAIK does not even support -std) has support for it:
https://msdn.microsoft.com/en-us/library/hh874894(v=vs.110).aspx

Clang since 3.1:
https://clang.llvm.org/cxx_status.html

> Maybe an actual check for it would be needed if --std=c++11 isn't available.

Well, only decklink_enc needs this, so if we really want to check this, 
and fail, if not, then it should be done somewhere after checking for 
decklink stuff. I don't particularly think that is very useful, but can do 
it if you think so.

Regards,
Marton


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