[LTP] [PATCH] Avoid compiler optimisation of malloc calls

[Chris Dearman <chris@mips.com>]

clang understands the malloc library call and can optimise calls to
it. In particular it will avoid calling malloc completely if it
detects that the result is not used.

Signed-off-by: Chris Dearman <chris@mips.com>
---
  .../conformance/interfaces/pthread_cond_init/4-1.c |   19 
++++++++++++-------
  1 files changed, 12 insertions(+), 7 deletions(-)

diff --git 
a/testcases/open_posix_testsuite/conformance/interfaces/pthread_cond_init/4-1.c 
b/testcases/open_posix_testsuite/conformance/interfaces/pthread_cond_init/4-1.c
index 287fda1..7932ec2 100644
--- 
a/testcases/open_posix_testsuite/conformance/interfaces/pthread_cond_init/4-1.c
+++ 
b/testcases/open_posix_testsuite/conformance/interfaces/pthread_cond_init/4-1.c
@@ -50,7 +50,7 @@
  #define ERR_MSG(f, rc) printf("Failed: func: %s rc: %s (%u)\n", \
  			f, strerror(rc), rc);
  -/* Max memory for child is 81B */
+/* Max memory for child is 1MB */
  #define MAX_MEM	((1<<20))
   /*
@@ -59,8 +59,8 @@
   */
  static void child(void)
  {
-	char *curr;
-	char *prev = NULL;
+	void *curr;
+	void *prev = NULL;
  	struct rlimit rl;
  	pthread_cond_t cond;
  	pthread_condattr_t attr;
@@ -76,10 +76,15 @@ static void child(void)
  		exit(PTS_UNRESOLVED);
  	}
  -	/* Consume all memory we can */
-	do {
-		curr = malloc(1);
-	} while (curr);
+	/*
+	 * Consume all memory we can
+	 * It's important to use the malloc() return value in a
+	 * meaningful way to bypass potential compiler optimisations.
+	 */
+	while ((curr = malloc(sizeof(void *)))) {
+		*(void **)curr = prev;
+		prev = curr;
+	}
  	if (errno != ENOMEM) {
  		ERR_MSG("malloc()", errno);
  		exit(PTS_UNRESOLVED);
-- 
1.7.1


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