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From:	"Gerald S. Williams" <gsw AT agere DOT com>
To:	"Andrew T. Schnable" <schnable AT enteract DOT com>,
	"Robert Collins" <robert DOT collins AT itdomain DOT com DOT au>, <cygwin AT cygwin DOT com>
Subject:	RE: sem_trywait returns EAGAIN (rather than returning -1 and setting errno)
Date:	Mon, 4 Mar 2002 11:06:02 -0500
Message-ID:	<GBEGLOMMCLDACBPKDIHFGEFLCHAA.gsw@agere.com>
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Andrew T. Schnable [mailto:schnable AT enteract DOT com] wrote:
> I think all the sem_* functions are broken similarly. [ ... ]

I just came across this myself while working on enabling
Cygwin Python threads. You may find the following function
helpful:

static int
fix_status(int status)
{
	return (status == -1) ? errno : status;
}

I defined it as a routine rather than a macro so that you
can use it on a single line without mistakenly calling
the function twice. E.g.,
	status = fix_status(sem_wait(thelock));

This should work for any function that returns 0 for success
and -1 for failure (putting the error code in errno), since
0 is never a legal errno code. You may find it useful if you
are using pthreads and semaphore code at the same time and
want the return codes to work the same.

-Jerry

-O Gerald S. Williams, 22Y-103GA : mailto:gsw AT agere DOT com O-
-O AGERE SYSTEMS, 555 UNION BLVD : office:610-712-8661  O-
-O ALLENTOWN, PA, USA 18109-3286 : mobile:908-672-7592  O-


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