[PATCH] cmake: fix sync_file_range detection

[Vladimir Davydov]

On Mon, Oct 08, 2018 at 06:04:08AM +0300, Alexander Turenko wrote:
> On Sat, Oct 06, 2018 at 05:51:48PM +0300, Vladimir Davydov wrote:
> > sync_file_range is declared only if _GNU_SOURCE macro is defined.
> > Also, in order to be used in a source file, HAVE_SYNC_FILE_RANGE
> > must be present in config.h.cmake.
> > 
> > Fixes commit caae99e5eaa0 ("Refactor xlog writer").
> > ---
> > https://github.com/tarantool/tarantool/commits/dv/cmake-fix-gnu-symbol-detection
> > 
> >  CMakeLists.txt            | 2 ++
> >  src/trivia/config.h.cmake | 1 +
> >  2 files changed, 3 insertions(+)
> > 
> > diff --git a/CMakeLists.txt b/CMakeLists.txt
> > index bf68d187..b26d2abf 100644
> > --- a/CMakeLists.txt
> > +++ b/CMakeLists.txt
> > @@ -69,6 +69,8 @@ include(cmake/profile.cmake)
> >  include(cmake/module.cmake)
> >  include(cmake/thread.cmake)
> >  
> > +list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
> > +
> 
> cmake/os.cmake already has `add_definitions("-D_GNU_SOURCE")`, is that
> not sufficient?

Looks like not. I checked - sync_page_range isn't used on Linux without
this patch.