On 6/3/2016 12:14 PM, Dmitry Karasik wrote:
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.
I'm no perl expert, but this doesn't strike me as a good solution. It means that a specific gcc version is hard-coded into perl.
It seems to me that the bug is in perl's algorithm (in /usr/lib/perl5/5.22/ExtUtils/Liblist/Kid.pm) for finding libraries of the form -lfoo. There's a special case for Cygwin at line 171 that looks for foo.dll (if it hasn't found libfoo.dll.a), which is wrong for two reasons. First, it should look for cygfoo*.dll instead (or in addition). Second, it should look in the path, or at least in /usr/bin, rather than in libpth.
In the present case of -lgomp, it would have found /usr/bin/cyggomp-1.dll. Ken -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
