Hello,
I'd like to report a configuration bug in perl. The problem arises when a 3-rd
party module tries to build an extension using perl configuration with a
gcc-specific library.
Generally perl extensions don't have a way to specify library to link with
directly, they do that through ExtUtils::MakeMaker, the standard tool for that.
Which in turn tries to resolve '-llibname' using its own
compile-time-configured internal list of lib paths. Everything works so far
libraries are found in perl's libpth (see by running 'perl -V:libpth') which is
/usr/lib on my machine. The problem arises when I need to link together with
libgomp, which is not found there, being a gcc-version-specific library.
For example, the following minimal Makefile.PL configure script
use ExtUtils::MakeMaker;
WriteMakefile(NAME => 'foo', LIBS => '-lgomp');
will emit a warning
Warning (mostly harmless): No library found for -lgomp
and removes -lgomp from the linker command, resulting in perl extension not
being able to compile.
The problem is confirmed, when, if I edit perl configuration file
/usr/lib/perl5/5.22/i686-cygwin-threads-64int/Config.pm, everything works:
ldlibpthname => 'PATH',
- libpth => '/usr/lib',
+ libpth => '/usr/lib /usr/lib/gcc/i686-pc-cygwin/5.3.0',
osname => 'cygwin',
I believe perl needs to be built with the properly set/found libpth in advance.
The diff below is the closest thing resembling a patch for the perl source
package I could come with:
--- Configure.0 2016-06-03 17:45:43.102008000 +0200
+++ Configure 2016-06-03 17:46:10.077558700 +0200
@@ -4948,6 +4948,16 @@
*) libpth="$libpth $j";;
esac
fi
+ # add gcc-specific libpath
+ if echo "$i" | grep -q "/usr/lib/gcc/"; then
+ j="`$echo $i|$sed 's,/include$,,'`"
+ if $test -d $j; then
+ case " $libpth " in
+ *" $j "*) ;;
+ *) libpth="$libpth $j";;
+ esac
+ fi
+ fi
done
libpth="`$echo $libpth|$sed 's/^ //'`"
for xxx in $libpth $loclibpth $plibpth $glibpth; do
The idea for the patch is taken from strawberry perl, which has the gcc libpath
included in configuration. I couldn't find though exactly how they manage to
include the path, during the configuration or when building, but it seems they
somehow add it explicitly, using a custom tool for the MinGW perl build:
https://github.com/StrawberryPerl/Perl-Dist-Strawberry/blob/master/share/portable/portable.perl.32#L60-L65
Hopefully this makes sense.
--
Sincerely,
Dmitry Karasik
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