diff --git a/AUTHORS b/AUTHORS
index ea7de2fb..3686cbb5 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -8,8 +8,12 @@ lib/libc.c (fopen)
 Han-Wen Nienhuys <hanwen@xs4all.nl>
 lib/libc+tcc.c (_memmem, memmem)
 
+
 List of imported files
 
+D A Gwyn
+lib/alloca.c
+
 Based on Guile ECMAScript
 module/language/c/lexer.mes
 
diff --git a/include/stdlib.h b/include/stdlib.h
index 36c21d8d..230291f2 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -34,6 +34,11 @@
 typedef unsigned long size_t;
 #endif
 
+#if _ALLOCA_UNSIGNED
+void * alloca (unsigned size);
+#else
+void * alloca (size_t size);
+#endif
 int atoi (char const *s);
 void * calloc (size_t nmemb, size_t size);
 void exit (int);
@@ -55,6 +60,9 @@ unsigned long long strtoull (char const *nptr, char **endptr, int base);
 #define EXIT_FAILURE 1
 #define EXIT_SUCCESS 0
 
+#ifndef NULL
+#define NULL 0
+#endif
 
 #if __MESC__
 typedef int (*comparison_fn_t) (void const *, void const *);
diff --git a/lib/alloca.c b/lib/alloca.c
new file mode 100644
index 00000000..53dbdc8a
--- /dev/null
+++ b/lib/alloca.c
@@ -0,0 +1,98 @@
+/* alloca.c -- allocate automatically reclaimed memory
+   (Mostly) portable public-domain implementation -- D A Gwyn
+
+   This implementation of the PWB library alloca function,
+   which is used to allocate space off the run-time stack so
+   that it is automatically reclaimed upon procedure exit,
+   was inspired by discussions with J. Q. Johnson of Cornell.
+
+   There are some preprocessor constants that can
+   be defined when compiling for your specific system, for
+   improved efficiency; however, the defaults should be okay.
+
+   The general concept of this implementation is to keep
+   track of all alloca-allocated blocks, and reclaim any
+   that are found to be deeper in the stack than the current
+   invocation.  This heuristic does not reclaim storage as
+   soon as it becomes invalid, but it will do so eventually.
+
+   As a special case, alloca(0) reclaims storage without
+   allocating any.  It is a good idea to use alloca(0) in
+   your main control loop, etc. to force garbage collection.  */
+
+#include <unistd.h>
+
+#define ALIGN_SIZE 4
+#define ADDRESS_FUNCTION(arg) &(arg)
+#define STACK_DIR -1
+
+union alloca_header
+{
+  char align[ALIGN_SIZE];	/* To force sizeof(union alloca_header).  */
+  struct
+    {
+      union alloca_header *next;		/* For chaining headers.  */
+      char *deep;		/* For stack depth measure.  */
+    } h;
+};
+
+static union alloca_header *last_alloca_header = NULL;	/* -> last alloca header.  */
+
+/* Return a void * to at least SIZE bytes of storage,
+   which will be automatically reclaimed upon exit from
+   the procedure that called alloca.  Originally, this space
+   was supposed to be taken from the current stack frame of the
+   caller, but that method cannot be made to work for some
+   implementations of C, for example under Gould's UTX/32.  */
+
+void *
+alloca (size_t size)
+{
+  char probe;		/* Probes stack depth: */
+  char *depth = ADDRESS_FUNCTION (probe);
+
+  /* Reclaim garbage, defined as all alloca'd storage that
+     was allocated from deeper in the stack than currently.  */
+
+  {
+    union alloca_header *hp;	/* Traverses linked list.  */
+
+    for (hp = last_alloca_header; hp != NULL;)
+      if ((STACK_DIR > 0 && hp->h.deep > depth)
+	  || (STACK_DIR < 0 && hp->h.deep < depth))
+	{
+	  union alloca_header *np = hp->h.next;
+
+	  free ((void *) hp);	/* Collect garbage.  */
+
+	  hp = np;		/* -> next header.  */
+	}
+      else
+	break;			/* Rest are not deeper.  */
+
+    last_alloca_header = hp;	/* -> last valid storage.  */
+
+  }
+
+  if (size == 0)
+    return NULL;		/* No allocation required.  */
+
+  /* Allocate combined header + user data storage.  */
+
+  {
+    void * new = malloc (sizeof (union alloca_header) + size);
+    /* Address of header.  */
+
+    if (new == 0)
+      abort();
+
+    ((union alloca_header *) new)->h.next = last_alloca_header;
+    ((union alloca_header *) new)->h.deep = depth;
+
+    last_alloca_header = (union alloca_header *) new;
+
+    /* User storage begins just after header.  */
+
+    return (void *) ((char *) new + sizeof (union alloca_header));
+  }
+}
diff --git a/lib/libc+gnu.c b/lib/libc+gnu.c
index 5cd48c23..abdedd34 100644
--- a/lib/libc+gnu.c
+++ b/lib/libc+gnu.c
@@ -23,4 +23,5 @@
 #include <m4.c>
 #include <binutils.c>
 #include <gcc.c>
+#include <alloca.c>
 #include <glibc.c>
diff --git a/lib/m4.c b/lib/m4.c
index f1e4ae7d..b4ff9c2e 100644
--- a/lib/m4.c
+++ b/lib/m4.c
@@ -19,7 +19,7 @@
  */
 
 int
-abort (int x)
+abort ()
 {
   eputs ("abort stub\n");
   return 0;