NetBSD Problem Report #58570

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Date: Sat, 10 Aug 2024 13:54:58 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: ATF_CHECK_ERRNO semantics and/or documentation is confusing
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>Number:         58570
>Category:       bin
>Synopsis:       ATF_CHECK_ERRNO semantics and/or documentation is confusing
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 10 14:00:00 +0000 2024
>Last-Modified:  Sat Aug 10 18:35:01 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The NetATF Errnodation
>Environment:
>Description:
Every time I read or reach for ATF_CHECK_ERRNO or ATF_REQUIRE_ERRNO, I have to look at the documentation to confirm what they mean.  That would be fine, except I don't understand what they are actually checking/requiring from the text in the man page:

     ATF_CHECK_ERRNO() and ATF_REQUIRE_ERRNO() take, first, the error code
     that the check is expecting to find in the errno variable and, second, a
     boolean expression that, if evaluates to true, means that a call failed
     and errno has to be checked against the first value.

So I have to look at the source code to confirm what they mean.

I think (I hope) what they mean is:

    ATF_CHECK_ERRNO(EWOTSIT, foo() == -1) checks that foo() == -1 is true, _and_ that errno == EWOTSIT.
>How-To-Repeat:
read or reach for ATF_CHECK_ERRNO/ATF_REQUIRE_ERRNO
>Fix:
Yes, please!

Clarifying the language in the man page would save me a lot of time.

>Audit-Trail:
From: Christoph Badura <bad@bsd.de>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: bin/58570: ATF_CHECK_ERRNO semantics and/or documentation is
 confusing
Date: Sat, 10 Aug 2024 18:43:30 +0200

 No, it is trying to say that it checks that if foo() == -1, then (errno ==
 EWOTSIT).
 I believe the idea is being able that if something fails, errno has the
 expected value.

 --chris

From: Robert Elz <kre@munnari.OZ.AU>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: bin/58570: ATF_CHECK_ERRNO semantics and/or documentation is confusing
Date: Sun, 11 Aug 2024 01:31:50 +0700

     Date:        Sat, 10 Aug 2024 16:45:02 +0000 (UTC)
     From:        Christoph Badura <bad@bsd.de>
     Message-ID:  <20240810164502.0E8C81A9244@mollari.NetBSD.org>

   |  No, it is trying to say that it checks that if foo() == -1, then (errno ==
   |  EWOTSIT).

 Yes, it tests that, but it also expects that foo() will return -1, and
 if it doesn't, the test has also failed.

   |  I believe the idea is being able that if something fails, errno has the
   |  expected value.

 Yes, but to test that reliably, the something has to actually fail.

 If something is coded (in a test) to fail, one might expect the test
 writer to know why it should fail, and hence which errno value should
 be produced.   Testing something that you expect might work (and hence
 must at least be plausibly correct) would make it difficult most of the
 time to know what might cause the error when it fails, and hence which
 errno value to expect.

 kre

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