diff --git a/include/ChangeLog b/include/ChangeLog
index 8eb61e64a..21ce68446 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,8 @@
+2001-03-06  Zack Weinberg  <zackw@stanford.edu>
+
+	* libiberty.h: Prototype C_alloca; define alloca to either
+	__builtin_alloca or C_alloca as appropriate.
+	
 2001-03-01  John David Anglin  <dave@hiauly1.hia.nrc.ca>
 
 	* safe-ctype.h (_sch_test): Cast enum bit to unsigned short int for pcc
diff --git a/include/libiberty.h b/include/libiberty.h
index 64d072be3..e4fc2af20 100644
--- a/include/libiberty.h
+++ b/include/libiberty.h
@@ -206,6 +206,20 @@ extern int vasprintf PARAMS ((char **, const char *, va_list))
 
 #define ARRAY_SIZE(a) (sizeof (a) / sizeof ((a)[0]))
 
+/* Drastically simplified alloca configurator.  If we're using GCC,
+   we use __builtin_alloca; otherwise we use the C alloca.  The C
+   alloca is always available.  You can override GCC by defining
+   USE_C_ALLOCA yourself.  */
+extern PTR C_alloca PARAMS((size_t));
+#undef alloca
+#if GCC_VERSION >= 2000 && !defined USE_C_ALLOCA
+# define alloca(x) __builtin_alloca(x)
+#else
+# define alloca(x) C_alloca(x)
+# undef USE_C_ALLOCA
+# define USE_C_ALLOCA 1
+#endif
+
 #ifdef __cplusplus
 }
 #endif