From cedda2084d2f6b331ba0a73e05f0b77ee7995c86 Mon Sep 17 00:00:00 2001
From: Stephen Dolan <mu@netsoc.tcd.ie>
Date: Mon, 24 Dec 2012 17:11:18 +0000
Subject: Sneaky valgrind trick to detect stack memory issues.

After something is popped from a stack, we overwrite the memory
with uninitialised data (if JQ_DEBUG is on). This means that
valgrind reports use-after-pop as an uninitialised memory error.
---
 jv_alloc.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'jv_alloc.h')

diff --git a/jv_alloc.h b/jv_alloc.h
index 0613d587..b4e72c0d 100644
--- a/jv_alloc.h
+++ b/jv_alloc.h
@@ -3,6 +3,17 @@
 
 #include <stddef.h>
 
+#if JQ_DEBUG
+extern volatile char jv_mem_uninitialised;
+#endif
+
+static void jv_mem_invalidate(void* mem, size_t n) {
+#if JQ_DEBUG
+  char* m = mem;
+  while (n--) *m++ ^= jv_mem_uninitialised ^ jv_mem_uninitialised;
+#endif
+}
+
 void* jv_mem_alloc(size_t);
 void jv_mem_free(void*);
 __attribute__((warn_unused_result)) void* jv_mem_realloc(void*, size_t);
-- 
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