Re: CHECK_SYMBOL_EXISTS and C++

Looking through SearchForStuff.cmake I've found one more thing:

CHECK_LIBRARY_EXISTS (rt clock_gettime "${PLAYER_EXTRA_LIB_DIRS}" 
HAVE_LIBRT)
SET (CMAKE_REQUIRED_LIBRARIES rt)
CHECK_FUNCTION_EXISTS (clock_gettime HAVE_CLOCK_GETTIME_FUNC)
SET (CMAKE_REQUIRED_LIBRARIES)
IF (HAVE_LIBRT AND HAVE_CLOCK_GETTIME_FUNC)
     SET (HAVE_CLOCK_GETTIME TRUE)
ENDIF (HAVE_LIBRT AND HAVE_CLOCK_GETTIME_FUNC)

On QNX clock_gettime is a part of libc. Due to last if, HAVE_CLOCK_GETTIME 
is set wrong way on QNX and replacement is (successfully at least!) used.

I'll try to prepare patch that correct it soon.

Paul

On Mon, 5 Jul 2010, Paul Osmialowski wrote:

> On Fri, 2 Jul 2010, Rich Mattes wrote:
>
>> There's an example of this in the check for TIMESPEC in
>> cmake/internal/SearchForStuff.cmake.  It's also how CMake does things like
>> CHECK_INCLUDE_FILES internally.
>>
>> http://www.cmake.org/Wiki/CMake:How_To_Write_Platform_Checks might help,
>> CHECK_C_SOURCE_COMPILES is at the bottom.
>>
>> Rich
>
> I looked at SearchForStuff.cmake and found some good examples, however, I
> wonder why in one file two different approaches are used:
>
> 1. CHECK_C_SOURCE_COMPILES (for me it would be CHECK_CXX_SOURCE_COMPILES):
>
>     INCLUDE (CheckCSourceCompiles)
>     SET (CHECK_TIMESPEC_SOURCE_CODE "#include <time.h>
> int main () { struct timespec *tmp; return 0; }")
>     CHECK_C_SOURCE_COMPILES ("${CHECK_TIMESPEC_SOURCE_CODE}"
> HAVE_STRUCT_TIMESPEC)
>
> 2. TRY_COMPILE (how does it know if it is C or C++?!):
>
> SET (testSTLSource ${CMAKE_CURRENT_BINARY_DIR}/CMakeTmp/test_stl.cpp)
> FILE (WRITE ${testSTLSource}
>     "#include <string>\nint main () {std::string a = \"blag\"; return
> 0;}\n")
> TRY_COMPILE (HAVE_STL ${CMAKE_CURRENT_BINARY_DIR} ${testSTLSource})
>
> Personally, I would take CHECK_CXX_SOURCE_COMPILES as it explicitly
> picks the right compiler. Both aproaches seem to be answers for my
> problem.
>
> Paul
>
>>
>> -----Original Message-----
>> From: Geoffrey Biggs [mailto:[email protected]]
>> Sent: Friday, July 02, 2010 2:51 AM
>> To: [email protected]
>> Subject: Re: [Playerstage-developers] CHECK_SYMBOL_EXISTS and C++
>>
>> You can supply CMake with a short program and instruct it to see if it
>> compiles, then based on the result decide if the feature that program
>> uses is supported or not.
>>
>> Geoff
>>
>> On 02/07/10 15:40, Paul Osmialowski wrote:
>>> Is it possible for cmake to check if some C++ stream modifier is defined?
>>> I doubt CHECK_SYMBOL_EXISTS is capable to do that. I'd like to modify
>>> CMakeLists.txt for epuck driver so it could check if std::showbase is
>>> defined in <iostream> (which is not in older g++).
>>>
>>> Paul
>>
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