Hi Peff,
On Tue, 9 Dec 2014, Jeff King wrote:
> On Mon, Dec 08, 2014 at 05:38:59PM +0100, Johannes Schindelin wrote:
>
> > At least on this developer's MacOSX (Snow Leopard, gcc-4.2.1), GCC prints
> > a warning that 'hash' may be used uninitialized when compiling
> > test-hashmap that 'hash' may be used uninitialized (but GCC 4.6.3 on this
> > developer's Ubuntu server does not report this problem).
> >
> > Since hash() is called from perf_hashmap() which accepts an unchecked
> > integer value from the command line, the warning appears to be legitimate,
> > even if the test-hashmap command is only called from the test suite.
>
> I think the older gcc is wrong;
Thanks for pointing to the older thread. It just happened to make it
inconvenient to develop the rather huge fsck api topic branch I submitted
yesterday because my vi kept jumping to test-hashmap.c because of that
compiler warning (and as you know, not everybody has the luxury of being
able to upgrade their gcc *cough* *Xcode* *cough* *Snow Leopard*).
> we are switching on "method & 3", which must be in the range 0-3 (and we
> cover all cases).
That is of course correct, but still does not address the compiler
warning.
Junio, you said that you would prefer the useless initialization, so here
goes:
-- snipsnap --
Subject: [PATCH] Avoid gcc compiler warning
At least on this developer's MacOSX (Snow Leopard, gcc-4.2.1), GCC prints
a warning that 'hash' may be used uninitialized when compiling
test-hashmap that 'hash' may be used uninitialized (but GCC 4.6.3 on this
developer's Ubuntu server does not report this problem).
The old compiler is wrong, of course, as the switch(method & 3) statement
already handles all the possible cases, but that does not help in a
scenario where it is hard or impossible to upgrade to a newer compiler
(e.g. being stuck on an older MacOSX and having to rely on Xcode).
So let's just initialize the variable and be done with it, it is hardly a
crucial part of the code because it is only used by the test suite and
invisible to the end users.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
test-hashmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/test-hashmap.c b/test-hashmap.c
index 07aa7ec..cc2891d 100644
--- a/test-hashmap.c
+++ b/test-hashmap.c
@@ -47,7 +47,7 @@ static struct test_entry *alloc_test_entry(int hash,
char *key, int klen,
static unsigned int hash(unsigned int method, unsigned int i, const char
*key)
{
- unsigned int hash;
+ unsigned int hash = 0;
switch (method & 3)
{
case HASH_METHOD_FNV:
--
2.0.0.rc3.9669.g840d1f9
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