Index: b/usr/src/head/stdlib.h
===================================================================
--- a/usr/src/head/stdlib.h
+++ b/usr/src/head/stdlib.h
@@ -41,6 +41,11 @@
 #include <sys/wait.h>
 #endif
 
+#if defined(_GNU_SOURCE) || defined(__EXTENSIONS__)
+# include <alloca.h>
+#endif
+
+
 /*
  * Allow global visibility for symbols defined in
  * C++ "std" namespace in <iso/stdlib_iso.h>.