[CMake] CheckFunctionExists.c on windows

[nikita kozlov]

Hello,
On windows you need to add some #include to be able to link with some libs.

Example, if i want to check the existence of socket() function, i need 
to link with ws2_32.lib, but i need to include winsock2.h too for some 
defines purpose.

a small cmake example:

if(WIN32)
    set(CMAKE_REQUIRED_LIBRARIES ws2_32.lib)
    set(CMAKE_REQUIRED_FLAGS /FIwinsock2.h)
endif(WIN32)
CHECK_FUNCTION_EXISTS(socket)

A patch proposal :

diff -rU4 CMakeA/Modules/CheckFunctionExists.c 
CMakeB/Modules/CheckFunctionExists.c
--- CMakeA/Modules/CheckFunctionExists.c    2004-04-15 
14:22:19.000000000 +0200
+++ CMakeB/Modules/CheckFunctionExists.c    2009-12-30 
15:29:07.000000000 +0100
@@ -1,15 +1,18 @@
 #ifdef CHECK_FUNCTION_EXISTS
 
+#ifndef _MSC_VER
 char CHECK_FUNCTION_EXISTS();
+#endif /* _MSC_VER */
+
 #ifdef __CLASSIC_C__
 int main(){
   int ac;
   char*av[];
 #else
 int main(int ac, char*av[]){
 #endif
-  CHECK_FUNCTION_EXISTS();
+  static void * p = (void*) CHECK_FUNCTION_EXISTS;
   if(ac > 1000)
     {
     return *av[0];
     }


-- 
nikita
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