42401: workaround for gcc -foptimize-strlen oddit.

Use realloc(NULL, ...) instead of malloc in zsh-mem calloc().

2 files changed, 10 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 099f5ce90..b2054f4f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2018-02-26  Peter Stephenson  <p.w.stephenson@ntlworld.com>
 
+	* Joey Pabalinas: 42401: Src/mem.c: replace malloc with use of
+	realloc to work around crash with gcc using -foptimize-strlen.
+
 	* users/23169: Completion/Base/Completer/_expand: treat ~[...]
 	the same way is other forms of tilde expansion: only expand
 	if accept-exact is set.
diff --git a/Src/mem.c b/Src/mem.c
index 840bbb6e4..f1208197b 100644
--- a/Src/mem.c
+++ b/Src/mem.c
@@ -1719,7 +1719,13 @@ calloc(MALLOC_ARG_T n, MALLOC_ARG_T size)
     if (!(l = n * size))
 	return (MALLOC_RET_T) m_high;
 
-    r = malloc(l);
+    /*
+     * use realloc() (with a NULL `p` argument it behaves exactly the same
+     * as malloc() does) to prevent an infinite loop caused by sibling-call
+     * optimizations (the malloc() call would otherwise be replaced by an
+     * unconditional branch back to line 1719 ad infinitum).
+     */
+    r = realloc(NULL, l);
 
     memset(r, 0, l);