On Tue, Jul 15, 2014 at 02:38:36PM +0200, Michal Privoznik wrote:
Up to now it's possible to do something like this:
const char *ptr;
ptr = strdup("my example string");
VIR_FREE(ptr);
The problem is, const char * pointers should not be modified (and
freeing them is kind of modification). We should avoid this. A little
trick is used: assigning a const pointer into 'void *' triggers
compiler warning about discarding 'const' qualifier from pointer. So
the virFree() function gains new dummy argument, that is not touched
anyhow, just fulfills the const correctness check duty.
Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
src/util/viralloc.c | 6 ++++--
src/util/viralloc.h | 20 ++++++++++++++++----
src/xenapi/xenapi_utils.c | 2 +-
3 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/src/util/viralloc.c b/src/util/viralloc.c
index be9f0fe..0134e67 100644
--- a/src/util/viralloc.c
+++ b/src/util/viralloc.c
[...]
@@ -569,13 +569,15 @@ int virAllocVar(void *ptrptr, /** * virFree: + * @ptr: dummy pointer to check const correctness * @ptrptr: pointer to pointer for address of memory to be freed * * Release the chunk of memory in the pointer pointed to by * the 'ptrptr' variable. After release, 'ptrptr' will be * updated to point to NULL. */ -void virFree(void *ptrptr) +void virFree(void *ptr ATTRIBUTE_UNUSED, + void *ptrptr)
What if you don't add another argument, but just change the void *ptrptr to void **ptrptr. Compiler shouldn't be mad about not knowing the size resulting of de-referencing ptrptr, you get the check you want and keep the macro without side-effects. Martin
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