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authorMichael Biebl <mbiebl@gmail.com>2016-07-27 05:32:37 +0200
committerZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2016-07-26 23:32:37 -0400
commitb6b609dbc202e5645fc58e87b8a7d46426ee4bb7 (patch)
tree6bb47c6c386bffcb1de3b12a24aaa335c0e4d3ca /src
parent5a8ff0e61dd8094b2b5d0b35df2ca13b489e0dfa (diff)
string-util: rework memory_erase() to not use GCC optimize attribute (#3812)
"#pragma GCC optimize" is merely a convenience to decorate multiple functions with attribute optimize. And the manual has this to say about this attribute: This attribute should be used for debugging purposes only. It is not suitable in production code. Some versions of GCC also seem to have a problem with this pragma in combination with LTO, resulting in ICEs. So use a different approach (indirect the memset call via a volatile function pointer) as implemented in openssl's crypto/mem_clr.c. Closes: #3811
Diffstat (limited to 'src')
-rw-r--r--src/basic/string-util.c26
1 files changed, 11 insertions, 15 deletions
diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index e9856b90d3..5d4510e1b3 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -22,6 +22,7 @@
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
+#include <string.h>
#include "alloc-util.h"
#include "gunicode.h"
@@ -822,25 +823,20 @@ int free_and_strdup(char **p, const char *s) {
return 1;
}
-#pragma GCC push_options
-#pragma GCC optimize("O0")
+/*
+ * Pointer to memset is volatile so that compiler must de-reference
+ * the pointer and can't assume that it points to any function in
+ * particular (such as memset, which it then might further "optimize")
+ * This approach is inspired by openssl's crypto/mem_clr.c.
+ */
+typedef void *(*memset_t)(void *,int,size_t);
-void* memory_erase(void *p, size_t l) {
- volatile uint8_t* x = (volatile uint8_t*) p;
-
- /* This basically does what memset() does, but hopefully isn't
- * optimized away by the compiler. One of those days, when
- * glibc learns memset_s() we should replace this call by
- * memset_s(), but until then this has to do. */
-
- for (; l > 0; l--)
- *(x++) = 'x';
+static volatile memset_t memset_func = memset;
- return p;
+void* memory_erase(void *p, size_t l) {
+ return memset_func(p, 'x', l);
}
-#pragma GCC pop_options
-
char* string_erase(char *x) {
if (!x)