Digression: use of perror() (Re: High speed serial I/O under system load)

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Article #1157

#1157

From: Peter da Silva
Date: Thu, 18 Jul 1991 14:06

16 lines
2097 bytes

Please respect followups. This digression has nothing to do with write()
problems (though I suspect an interrupted system call).

In article <1991Jul17.174348.24529@world.std.com> jaa@world.std.com (Jerry A Abramson) writes:
>         fprintf(stderr,"\n\rvtko: Write Failure\n\r");
>         perror("vtko");

Suggestion: put the perror() before the fprintf(). It is possible for fprintf
to clobber errno, guaranteeing a bogus response.

Alternative: save errno before the fprintf and restore it afterwards.

Moral: never call perror() except immediately after a failed system call.
-- 
Peter da Silva; Ferranti International Controls Corporation; +1 713 274 5180;
Sugar Land, TX  77487-5012;         `-_-' "Have you hugged your wolf, today?"

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References: <wd.678549611@distel> <1991Jul17.174348.24529@world.std.com>

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From: peter@ficc.ferranti.com (Peter da Silva)
Newsgroups: comp.bugs.sys5,comp.unix.internals,comp.unix.questions,comp.unix.sysv386,biz.sco.opendesktop,comp.lang.c,comp.unix.programmer
Subject: Digression: use of perror() (Re: High speed serial I/O under system load)
Keywords: SVR3, i386, tty, flow control
Message-ID: <QBPCR92@xds13.ferranti.com>
Date: 18 Jul 91 14:06:52 GMT
References: <wd.678549611@distel> <1991Jul17.174348.24529@world.std.com>
Reply-To: peter@ficc.ferranti.com (Peter da Silva)
Followup-To: comp.lang.c,comp.unix.programmer
Organization: Xenix Support, FICC
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