[CMake] compiling single source with different flags

[Michael Wild]

On 29. Dec, 2009, at 21:44 , Eric Noulard wrote:

> 2009/12/29 Richard Wackerbarth <richard at nfsnet.org>:
>> Not as a "real" solution, but more as a "workaround", you could create a "derived source file" which is just a copy of the source file and then you would have two separate files to be compiled with the appropriate flags.
> 
> That's one solution, see below for more information.
> 
>> On Dec 29, 2009, at 2:22 PM, Bart wrote:
>> 
>>> Hi,
>>> 
>>> I'm trying to find a way to build a library with two different instances of the same source file.
>>> for example I would like to compile foo.c with -DDINT into foo_int.o and with -DDLONG into foo_long.o
>>> and have both objects added to the same library libfoo.a
>>> 
>>> I have experimented with custom command to generate the source files (which did not work), and would have still
>>> left me with how to compile them with different -D flags.
> 
> Same kind of question has been asked on the ML recently,
> may be you can re-read the thread
> http://www.cmake.org/pipermail/cmake/2009-December/033813.html
> 

Or you can use CONFIGURE_FILE to create "wrappers" which #include the actual source file. If it's always the same flags, you can do it statically, using something like this:

wrap_foo.c:
/* -------------------------- */
/* clean up */
#ifdef DINT
#undef DINT
#endif
#ifdef DLONG
#undef DLONG
#endif

/* compile for int */
#define DINT
#include "foo.c"
#undef DINT

/* compile for long */
#define DLONG
#include "foo.c"
#endif 
/* -------------------------- */

Michael