Re: segmentation fault with {1..1234567}

[Bart Schaefer <schaefer@brasslantern.com>]

On Jul 7,  8:33pm, Peter Stephenson wrote:
} Subject: Re: segmentation fault with {1..1234567}
}
} On Sun, 06 Jul 2014 12:46:29 -0700
} Bart Schaefer <schaefer@brasslantern.com> wrote:
} > The question is, do we fix this one instance (your patch), do we redefine
} > VARARR() [possibly conditionally] to change all the usages at once, or do
} > we individually evaluate the 50-odd uses of VARARR()?
} 
} Probably the third option is the right one, but it's the most work.  The
} other possibilities are the pragmatic option of only fixing things when
} they turn out to be buggy, or changing everything to heap allocation (or
} something else known not to be problematic).  The best argument for the
} last one is that it removes quite a lot of variant behaviour between
} systems --- even if using zhalloc() isn't particularly efficient we can
} all see whatever effects there are and are in a better position to fix
} them (e.g. with appropriate heap manipulation commands).  For that
} reason, I'm vaguely wondering if trying out that might not be a
} reasonable start.

Well, that one is easy, as I mentioned earlier; see patch below.  One added
hunk in mem.c for a place where we didn't check the return of malloc, but I
did not attempt to change the usual fatal-error behavior.


diff --git a/Src/mem.c b/Src/mem.c
index a8f0c37..7e0667a 100644
--- a/Src/mem.c
+++ b/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();
 
diff --git a/Src/zsh_system.h b/Src/zsh_system.h
index 601de69..811340d 100644
--- a/Src/zsh_system.h
+++ b/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                                 */
diff --git a/configure.ac b/configure.ac
index 0f87a6c..37f3585 100644
--- a/configure.ac
+++ b/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,