Date: Fri, 16 Jan 2009 11:21:22 +0100 From: Christoph Mallon <christoph.mallon@gmx.de> To: Christian Kandeler <christian.kandeler@hob.de> Cc: 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: <49705FA2.2020605@gmx.de> In-Reply-To: <200901161039.00232.christian.kandeler@hob.de> References: <7d6fde3d0901160041n55466290l55f737d274a40895@mail.gmail.com> <49704AEC.3080709@gmx.de> <200901161039.00232.christian.kandeler@hob.de>
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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().
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