Re: CHECK_SYMBOL_EXISTS and C++

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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