32853: redefine VARARR() to use heap rather than stack allocation

enable old behavior via "configure --with-stack-allocation"

ChangeLog

@@ -1,5 +1,9 @@
 2014-07-24  Barton E. Schaefer  <schaefer@zsh.org>
 
+	* 32853: configure.ac, Src/mem.c, Src/zsh_system.h: redefine
+	the VARARR() macro to use heap rather than stack allocation;
+	enable old behavior via "configure --with-stack-allocation"
+
 	* unposted (see 32892): Src/builtins.c: 'fc -I' is an error
 
 	* 32903: Src/Modules/parameter.c: new empty (unset) elements in

Src/mem.c

@@ -950,7 +950,10 @@ zrealloc(void *ptr, size_t size)
 	ptr = NULL;
     } else {
 	/* If ptr is NULL, then behave like malloc */
-	ptr = malloc(size);
+        if (!(ptr = (void *) malloc(size))) {
+            zerr("fatal error: out of memory");
+            exit(1);
+        }
     }
     unqueue_signals();
 

Src/zsh_system.h

@@ -286,11 +286,15 @@ struct timezone {
 # include <limits.h>
 #endif
 
+#ifdef USE_STACK_ALLOCATION
 #ifdef HAVE_VARIABLE_LENGTH_ARRAYS
 # define VARARR(X,Y,Z)	X (Y)[Z]
 #else
 # define VARARR(X,Y,Z)	X *(Y) = (X *) alloca(sizeof(X) * (Z))
 #endif
+#else
+# define VARARR(X,Y,Z)	X *(Y) = (X *) zhalloc(sizeof(X) * (Z))
+#endif
 
 /* we should handle unlimited sizes from pathconf(_PC_PATH_MAX) */
 /* but this is too much trouble                                 */

configure.ac

@@ -140,6 +140,16 @@ AC_HELP_STRING([--enable-zsh-hash-debug], [turn on debugging of internal hash ta
   AC_DEFINE(ZSH_HASH_DEBUG)
 fi])
 
+dnl Do you want to dynamically allocate memory on the stack where possible?
+ifdef([stack-allocation],[undefine([stack-allocation])])dnl
+AH_TEMPLATE([USE_STACK_ALLOCATION],
+[Define to 1 if you want to allocate stack memory e.g. with `alloca'.])
+AC_ARG_ENABLE(stack-allocation,
+AC_HELP_STRING([--enable-stack-allocation], [allocate stack memory e.g. with `alloca']),
+[if test x$enableval = xyes; then
+  AC_DEFINE(USE_STACK_ALLOCATION)
+fi])
+
 dnl Pathnames for global zsh scripts
 ifdef([etcdir],[undefine([etcdir])])dnl
 AC_ARG_ENABLE(etcdir,