Am 07.12.2015 um 21:31 schrieb Junio C Hamano:
Stefan Naewe <stefan.naewe@xxxxxxxxx> writes:
mark_tree_uninteresting dereferences a tree pointer before checking
if the pointer is valid. Fix that by doing the check first.
Signed-off-by: Stefan Naewe <stefan.naewe@xxxxxxxxx>
---
I still have a problem with "dereferences", as "dereference" is
about computing an address and accessing memory based on the result,
and only the first half is happening here. I can live with "The
function does a pointer arithmetic on 'tree' before it makes sure
that 'tree' is not NULL", but in any case, let's queue this as-is
for now and wait for a while to see if others can come up with a
more appropriate phrases.
Don't shoo away language lawyers, because this is a pure C language rule
patch. If this were only about pointer arithmetic, a change would not be
necessary. But it isn't. The patch corrects a case where the compiler
can remove a NULL pointer check that we actually want to remain. The
language rule that gives sufficient room for interpretation to the
compiler is about dereferencing a pointer. It is irrelevant that an
address of an object is taken after the dereference and then only
pointer arithmetic remains---the dereference has already taken place,
and that cannot occur for a NULL pointer in a valid program. So, the
phrase "dereference" is precise and correct here.
-- Hannes
Thanks.
revision.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/revision.c b/revision.c
index 0fbb684..8c569cc 100644
--- a/revision.c
+++ b/revision.c
@@ -135,10 +135,12 @@ static void mark_tree_contents_uninteresting(struct tree *tree)
void mark_tree_uninteresting(struct tree *tree)
{
- struct object *obj = &tree->object;
+ struct object *obj;
if (!tree)
return;
+
+ obj = &tree->object;
if (obj->flags & UNINTERESTING)
return;
obj->flags |= UNINTERESTING;
--
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