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Date: Tue, 25 Oct 2016 22:50:50 +0200
From: "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
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To: djgpp AT delorie DOT com
Subject: Re: A grep 2.26 test fails because fopen sets errno to EACCES when
 openning an existing directory.
References: <580BCAA5 DOT 2000304 AT gmx DOT de> <83d1irppmj DOT fsf AT gnu DOT org> <580D0638 DOT 8080605 AT gmx DOT de> <numomu$png$1 AT gioia DOT aioe DOT org>
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Reply-To: djgpp AT delorie DOT com

Am 25.10.2016 06:57, schrieb Martin Str|mberg (ams AT ludd DOT luth DOT se) [via djgpp AT delorie DOT com]:
> "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via djgpp AT delorie DOT com]"<djgpp AT delorie DOT com>  wrote:
>> I have compiled grep-2.26 with cygwin, debian 8.2.0 and openSUSE 11.4 (my linux box).
>> They all return EISDIR for the failing fread.  These seems to indicate that
>> EISDIR is the defacto value that have been choosen for this fread failure.
>
> How about looking at the documentation?
>
> fread() isn't documented to use errno (not in C99 (sorry that's the
> latest I have, nor in the latest man page for linux
> <http://man7.org/linux/man-pages/man3/fread.3.html>  (I arrived there
> from<https://www.kernel.org/doc/man-pages/>)), so you've found a bug
> in the test suite as in that case it's plainly wrong to look at errno.
>
>
> However, you are one of the few maintaining poor DJGPP, so you're
> welcome to do what you see fit.
>
>

IMHO, there is neither an error in grep nor in the testsuite.  They simple
expect a posix comforming behavior of fopen and fread.  According to the
man pages of my almost 10-year old linux box the following shall hold for
a posix conforming fread (verbatim copy):

RETURN VALUE
        Upon  successful  completion,  fread() shall return the number of ele-
        ments successfully read which is less than nitems only if a read error
        or  end-of-file  is encountered. If size or nitems is 0, fread() shall
        return 0 and the contents of the array and the  state  of  the  stream
        remain unchanged. Otherwise, if a read error occurs, the error indica-
        tor for the stream shall be set,  and errno shall be set  to  indicate
        the error.

I have also inspected http://pubs.opengroup.org/onlinepubs/009695399/functions/fread.html
and it states the same.  Unfortunately nobody says what the errnos are.

But I fear that the issue is far more complicated.  The errno itself is not
really important.  Important is the exit value of grep and this should be 2
but it is 1 for the DJGPP port.  The test issues the following command:
   ./grep -f a/ < /dev/null
and a/ is an empty directory.  The directory is open using fopen and read
using fread.  On linux and djgpp fread returns with a value of zero and the
error status is indagated using ferror.  The linux port returns with some error
and terminates the program immediately with grep status = 2 meanwhile the djgpp
port sees no error at all an continues running until it finishes with grep
status = 1 making the check fail.  I still have not figured out what is going
on here.  I will see how to fix all this.

Regards,
Juan M. Guerrero