Date: Fri, 16 Jan 2009 02:44:27 -0800 From: Garrett Cooper <yanefbsd@gmail.com> To: Christoph Mallon <christoph.mallon@gmx.de> Cc: Christian Kandeler <christian.kandeler@hob.de>, freebsd-hackers@freebsd.org Subject: Re: Confused by segfault with legitimate call to strerror(3) on amd64 / sysctl (3) setting `odd' errno's Message-ID: <7d6fde3d0901160244r6d72a3f1k5c27ea03fbc37ef5@mail.gmail.com> In-Reply-To: <7d6fde3d0901160235o6aa1f096q11c5096b70f3577@mail.gmail.com> References: <7d6fde3d0901160041n55466290l55f737d274a40895@mail.gmail.com> <49704AEC.3080709@gmx.de> <200901161039.00232.christian.kandeler@hob.de> <49705FA2.2020605@gmx.de> <7d6fde3d0901160235o6aa1f096q11c5096b70f3577@mail.gmail.com>
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On Fri, Jan 16, 2009 at 2:35 AM, Garrett Cooper <yanefbsd@gmail.com> wrote:
> On Fri, Jan 16, 2009 at 2:21 AM, Christoph Mallon
> <christoph.mallon@gmx.de> wrote:
>> Christian Kandeler schrieb:
>>>
>>> On Friday 16 January 2009 09:53, Christoph Mallon wrote:
>>>
>>>>> int
>>>>> main() {
>>>>>
>>>>> int mib[4];
>>>>>
>>>>> size_t len;
>>>>>
>>>>> if (sysctlnametomib("kern.ipc.shmmax", mib, &len) != 0) {
>>>>> printf("Errno: %d\n", errno);
>>>>> errx(errno, "Error: %s", strerror(errno));
>>>>
>>>> The use of errno is wrong. printf might change errno.
>>>
>>> I don't think printf() can set errno. And even if it could, it
>>
>> Of course it can. See ISO/IEC 9899:1999 (E) §7.5:3.
>>
>>> wouldn't matter, because C has call-by-value semantics.
>>
>> This has nothing to do with call-by-value. errno is read (even twice!)
>> *after* the call to printf().
>
> Ok, I just installworld'ed, recompiled the program with the
> following modifications, and I still get segfaults. And the question
> of the night is: why amd64 on a VERY recent CURRENT?
> I'm going to try the same app on an amd64 freebsd VMware instance
> with RELENG_7.
> Remember: just because a bunch of other people aren't reporting
> issues with CURRENT/amd64 doesn't mean that it isn't environmental,
> related to my hardware or compile options ;).
> Cheers,
> -Garrett
Ugh... I pasted it twice by accident. Sorry.
-Garrett
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