In shorten_unambiguous_ref, we build and cache a reverse-map of the
rev-parse rules like this:
static char **scanf_fmts;
static int nr_rules;
if (!nr_rules) {
for (; ref_rev_parse_rules[nr_rules]; nr_rules++)
... generate scanf_fmts ...
}
where ref_rev_parse_rules is terminated with a NULL pointer.
Compiling with gcc -O2 -Wall does not cause any problems, but
compiling with -O3 -Wall generates:
$ make CFLAGS='-O3 -Wall' refs.o
refs.c: In function ‘shorten_unambiguous_ref’:
refs.c:3379:29: warning: array subscript is above array bounds
[-Warray-bounds]
for (; ref_rev_parse_rules[nr_rules]; nr_rules++)
Curiously, we can silence this by explicitly nr_rules to 0
in the beginning of the loop, even though the compiler
should be able to tell that we follow this code path only
when nr_rules is already 0.
Signed-off-by: Jeff King p...@peff.net
---
I've convinced myself that this is a gcc bug and not some weird
undefined behavior or extra analysis that gcc can do due to inlined
functions. The fact that what should be a noop makes the warning go away
makes me very suspicious.
You can also silence it by declaring ref_rev_parse_rules as:
const char * const ref_rev_parse_rules[];
to make both the strings themselves and the pointers in the list
constant. And that may be worth doing instead, because it really is
a constant list for us. The downside is that it's a little uglier to
read, and it carries over to pointers we use to access it, like:
const char * const *p;
for (p = ref_rev_parse_rules; *p; p++)
...
refs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/refs.c b/refs.c
index ad5d66c..c1cc98a 100644
--- a/refs.c
+++ b/refs.c
@@ -3376,7 +3376,7 @@ char *shorten_unambiguous_ref(const char *refname, int
strict)
size_t total_len = 0;
/* the rule list is NULL terminated, count them first */
- for (; ref_rev_parse_rules[nr_rules]; nr_rules++)
+ for (nr_rules = 0; ref_rev_parse_rules[nr_rules]; nr_rules++)
/* no +1 because strlen(%s) strlen(%.*s) */
total_len += strlen(ref_rev_parse_rules[nr_rules]);
--
1.8.4.1.4.gf327177
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