Handle <alloca.h> better

 - Test for existence, assume symbols/functionality provided elsewhere
   if it is missing. Should induce compile time error if this is not
   true.

Author: zbeekman

src/mpi/CMakeLists.txt

@@ -28,6 +28,13 @@ if(CAF_EXPOSE_INIT_FINALIZE)
   add_definitions(-DEXPOSE_INIT_FINALIZE)
 endif()
 
+include(CheckIncludeFile)
+CHECK_INCLUDE_FILE("alloca.h" HAVE_ALLOCA)
+if(NOT HAVE_ALLOCA)
+  add_definitions(-DALLOCA_MISSING)
+  message(WARNING "Could not find <alloca.h>. Assuming functionality is provided elsewhere.")
+endif()
+
 #----------------------------------------------------------------------
 # Test if MPI implementation provides features needed for failed images
 #----------------------------------------------------------------------

src/mpi/mpi_caf.c

@@ -37,7 +37,9 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  */
 #include <stdlib.h>
 #include <string.h>        /* For memcpy.  */
 #include <stdarg.h>        /* For variadic arguments.  */
-#include <alloca.h>
+#ifndef ALLOCA_MISSING
+#include <alloca.h>        /* Assume functionality provided elsewhere if missing */
+#endif
 #include <unistd.h>
 #include <mpi.h>
 #include <pthread.h>