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Date: Tue, 04 Oct 2011 15:30:47 -0400
From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
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Subject: Re: ANSI C header files
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On 04/10/2011 9:05 AM, Kåre Edvardsen wrote:
> On Tue, Oct 4, 2011 at 12:13 PM, Marco Atzeri  wrote:
> (snip)
>> Kare,
>> in addition to the TOFU advise,
>>
>> running configure of grib_api-1.9.9_libtool.tar.gz
>> on my XP-SP3 gave no problem.
>>
>> "Configuration completed."
>>
>> The ANSI C test is a basic one
>>
>> configure:6808: checking for ANSI C header files
>> configure:6828: gcc -c -g -O2  conftest.c>&5
>> configure:6828: $? = 0
>> configure:6901: gcc -o conftest.exe -g -O2   conftest.c>&5
>> configure:6901: $? = 0
>> configure:6901: ./conftest.exe
>> configure:6901: $? = 0
>> configure:6912: result: yes
>>
>> I reproduced the hang on my Cygwin CYGWIN_NT-6.0  1.7.9(0.237/5/3)
>> 2011-03-29 10:10 i686 Cygwin
>> and gcc version 4.5.3
>>
>> This appears to be the critical spot (line 6820-6828)
>>
>> if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
>>    $EGREP "memchr">/dev/null 2>&1; then
>>    :
>> else
>>    ac_cv_header_stdc=no
>> fi
>>
>> It tries to run the preprocessor and pipe its output into egrep.
>> Unfortunately, the EGREP variable appears to be empty, so the end
>> result is similar to:
>>
>> gcc -E conftest.c | memchr
>>
>> Trying the above from the bash prompt (in both mintty and classic
>> Cygwin prompt) results in an (unkillable from Cygwin) cc1.exe which is
>> perpetually waiting for output:
>>
>> $ ps
>>        PID    PPID    PGID     WINPID  TTY  UID    STIME COMMAND
>>       4484       1    4484       4752  con 539771   Oct  3 /usr/bin/XWin
>>       7848       1    7848       7848    ? 539771 14:03:11 /usr/bin/mintty
>>       6468    7848    6468       7460    1 539771 14:03:11 /usr/bin/bash
>>       6692       1    6692       6692    ? 539771 10:12:37 /usr/bin/mintty
>>       4600    6692    4600       7156    3 539771 10:12:37 /usr/bin/ssh
>>       6272    6468    6272       6356    1 539771 13:08:43 /usr/bin/gcc-4
>> O    7492    6272    6272       6856    1 539771 13:08:43
>> /usr/lib/gcc/i686-pc-cygwin/4.5.3/cc1
>>       7404    6468    7404        524    1 539771 13:08:46 /usr/bin/ps
>>
>>
>> So, the workaround is to replace $EGREP with egrep in configure; then
>> configure runs successfully.
>>
>> This seems to be some peculiarity of Cygwin's current GCC 4.5.3;
>> neither GCC 3.4.4 in Cygwin 1.7 nor GCC 4.3.4 in Cygwin 1.7 nor GCC
>> 4.3.2 in Cygwin 1.5 exhibit this hang.
>>
>> Csaba
> Csaba&  Marco.
>
> Marco: Your try on the XP-SP3 gave no problem. My try on Win 7 Pro
> hangs, but as Csaba points out: This seems to be some peculiarity of
> Cygwin's current GCC 4.5.3
>
> Csaba: Replacing $EGREP with egrep in configure did make the difference!
>
> Thanx to both of you for excellent help.
It wouldn't surprise me at all if the real problem were an earlier fork 
failure that caused $EGREP to come up blank. Why gcc would then hang on 
the resulting broken pipeline is a different question, tho...

Ryan


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