Whoops, it's malloc.h, not alloca.h ...

physfs_internal.h

@@ -25,14 +25,10 @@
 #endif
 
 /* !!! FIXME: remove this when revamping stack allocation code... */
-#ifdef _MSC_VER
+#if defined(_MSC_VER) || defined(__MINGW32__)
 #include <malloc.h>
 #endif
 
-#ifdef __MINGW32__
-#include <alloca.h>
-#endif
-
 #ifdef __cplusplus
 extern "C" {
 #endif