On 08/03/2017 01:38 PM, Greg Kurz wrote:
> The following code snippet spits a warning with gcc-7.1.1-3.fc26 and -Wall on
> ppc64le AND x86_64:
>
> int foo(void)
> {
> char empty_array[] = { };
> int i, ret = 0;
>
> for (i = 0; i < (int) (sizeof(empty_array) / sizeof(empty_array[0]));
> i++) {
> ret = empty_array[i];
> }
>
> return ret;
> }Confirmed. No idea why the cast makes gcc think i is uninitialized. > > If I drop the (int), the warning goes away... and so does the build break > of qemu-system-ppc64 on my ppc64le host. > > I don't have 4.7.1 or 4.6 compilers around but I could check 4.8.5 > is okay with that change FWIW. I tested with gcc 4.4.7 on RHEL 6, but -Wtype-limits there didn't warn whether or not the (int) was present; it's possible that we still need to test with 4.6 or 4.7.1 to see whether it makes a difference. > >> Ok so let's stop losing time about compiler incoherent warnings, using >> -Wno-type-limits for GCC < 5... >> So we can keep a sane/understandable codebase, using size_t and no (int) >> cast. That's also a possibility, if we still hit old compilers that require the (int). >> > > If I also convert 'int i' to 'size_t i' then I get the same error as > in commit 61c7bbd2: > > error: comparison of unsigned expression < 0 is always > false [-Werror=type-limits] Confirmed with newer gcc, whether or not the (int) cast is present. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature
