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Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value)
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value) |
Date: |
Fri, 28 Oct 2011 09:49:52 +0100 |
On Fri, Oct 28, 2011 at 8:40 AM, Markus Armbruster <address@hidden> wrote:
> Stefan Hajnoczi <address@hidden> writes:
>
>> On Mon, Oct 24, 2011 at 10:18:43PM +0200, Stefan Weil wrote:
>>> For compilations with -DNDEBUG, the default case did not return
>>> a value which caused a compiler warning.
>>>
>>> Signed-off-by: Stefan Weil <address@hidden>
>>> ---
>>> hw/ppce500_spin.c | 11 ++++++++---
>>> 1 files changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/hw/ppce500_spin.c b/hw/ppce500_spin.c
>>> index cccd940..5b5ffe0 100644
>>> --- a/hw/ppce500_spin.c
>>> +++ b/hw/ppce500_spin.c
>>> @@ -168,17 +168,22 @@ static uint64_t spin_read(void *opaque,
>>> target_phys_addr_t addr, unsigned len)
>>> {
>>> SpinState *s = opaque;
>>> uint8_t *spin_p = &((uint8_t*)s->spin)[addr];
>>> + uint64_t result = 0;
>>>
>>> switch (len) {
>>> case 1:
>>> - return ldub_p(spin_p);
>>> + result = ldub_p(spin_p);
>>> + break;
>>> case 2:
>>> - return lduw_p(spin_p);
>>> + result = lduw_p(spin_p);
>>> + break;
>>> case 4:
>>> - return ldl_p(spin_p);
>>> + result = ldl_p(spin_p);
>>> + break;
>>> default:
>>> assert(0);
>>
>> I would replace assert(3) with abort(3). If this ever happens the
>> program is broken - returning 0 instead of an undefined value doesn't
>> help.
>
> Why is it useful to make failed assertions stop the program regardless
> of NDEBUG only when the assertion happens to be "can't reach"?
My point is that it should not be an assertion. The program has a
control flow path which should never be taken. In any "safe"
programming environment the program will terminate with a diagnostic.
That's exactly what we need to do here too. assert(3) is the wrong
tool for this; we're not even asserting anything.
Stefan
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), (continued)
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Stefan Hajnoczi, 2011/10/26
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), introduce qemu_abort?, Stefan Weil, 2011/10/26
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), introduce qemu_abort?, Blue Swirl, 2011/10/26
- [Qemu-devel] [RFC] Introduce qemu_abort? (was: Fix compiler warning (always return a value)), Stefan Weil, 2011/10/26
- Re: [Qemu-devel] [RFC] Introduce qemu_abort? (was: Fix compiler warning (always return a value)), Blue Swirl, 2011/10/26
- Re: [Qemu-devel] [RFC] Introduce qemu_abort? (was: Fix compiler warning (always return a value)), Peter Maydell, 2011/10/26
- Re: [Qemu-devel] [RFC] Introduce qemu_abort?, Markus Armbruster, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), introduce qemu_abort?, Stefan Hajnoczi, 2011/10/27
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), introduce qemu_abort?, Alexander Graf, 2011/10/27
Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Markus Armbruster, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value),
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Markus Armbruster, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Stefan Hajnoczi, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Markus Armbruster, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Stefan Hajnoczi, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Markus Armbruster, 2011/10/28
- Re: [Qemu-devel] [PATCH] Fix compiler warning (always return a value), Paolo Bonzini, 2011/10/28