Re: [PATCH] Avoid gcc compiler warning
- From
Johannes Schindelin <johannes.schindelin@gmx.de>
- Date
- Dec 9, 2014, 09:48 UTC
- Message-ID
- <alpine.DEB.1.00.1412091039130.13845@s15462909.onlinehome-server.info>
- In-Reply-To
- <20141209084728.GA13123@peff.net>
Hi Peff,
On Tue, 9 Dec 2014, Jeff King wrote:
Show 12 quoted lines
> 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@gmx.de> --- 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