[RFC PATCH 03/15] reftable: don't memset() a NULL from failed malloc()

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Return NULL instead of possibly feeding a NULL to memset() in
reftable_calloc(). This issue was noted by GCC 12's -fanalyzer:

	reftable/publicbasics.c: In function ‘reftable_calloc’:
	reftable/publicbasics.c:43:9: error: use of possibly-NULL ‘p’ where non-null expected [CWE-690] [-Werror=analyzer-possible-null-argument]
	   43 |         memset(p, 0, sz);
	      |         ^~~~~~~~~~~~~~~~
	[...]

This bug has been with us ever since this code was added in
ef8a6c62687 (reftable: utility functions, 2021-10-07).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 reftable/publicbasics.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/reftable/publicbasics.c b/reftable/publicbasics.c
index 0ad7d5c0ff2..a18167f5ab7 100644
--- a/reftable/publicbasics.c
+++ b/reftable/publicbasics.c
@@ -40,6 +40,8 @@ void reftable_free(void *p)
 void *reftable_calloc(size_t sz)
 {
 	void *p = reftable_malloc(sz);
+	if (!p)
+		return NULL;
 	memset(p, 0, sz);
 	return p;
 }
-- 
2.36.1.1124.g577fa9c2ebd