[CMake] How to check for a symbol that requires two header files in CMake?

[Martin Sustrik]

Hi all,

I am trying to find out whether getifaddrs function is avialable.

To get symbol getifaddrs defined you have to include both sys/types.h 
and ifaddrs.h. Here's the synopsis of the function from the man page:

        #include <sys/types.h>
        #include <ifaddrs.h>

        int getifaddrs(struct ifaddrs **ifap);

When checking whether the symbol exists, I've tried the following:

set (CMAKE_EXTRA_INCLUDE_FILES sys/types.h)
check_symbol_exists (getifaddrs ifaddrs.h SP_HAVE_IFADDRS)
set (CMAKE_EXTRA_INCLUDE_FILES)

However, the generated test program still includes only ifaddrs.h and 
thus fails to detect the symbol.

How can I force it to include sys/types.h as well?

Martin