Re: Libtool, SWIG and testing

[Gavin Smith]

On 28 July 2015 at 16:58, Guillaume Marcais <address@hidden> wrote:
> On Sat, Jul 25, 2015 at 9:41 AM, Gavin Smith <address@hidden>
> wrote:
>
>>
>> I'd suggest not hard-coding the name of the shared library in the Perl
>> code. It could be extracted from the *.la file. That would likely
>> improve portability. I don't see any way to avoid looking in .libs.
>>
>>
> Thank you for your answer.
>
> In this case, the Perl code that loads the shared library is generated by
> SWIG (mummer.pm). It does use DynaLoader and calls "bootstrap mummer;". The
> Makefile.am part that builds this library reads:
>
> perlextdir = $(PERL_EXT_LIB)
> perlext_SCRIPTS = perl5/mummer.pm
> perlext_LTLIBRARIES = perl5/mummer.la
> perl5_mummer_la_SOURCES = perl5/swig_wrap.cpp $(SWIG_SRC)
>
> plus some other flags set in _CPPFLAGS, _LDFLAGS etc. Could really LIBTOOL
> build a shared object in the .libs directory that could not be loaded by
> "bootstrap mummer;"?

>From DynaLoader manpage:

 dl_findfile()
           Syntax:

               @filepaths = dl_findfile(@names)

           Determine the full paths (including file suffix) of one or more
           loadable files given their generic names and optionally one or more
           directories.  Searches directories in @dl_library_path by default
           and returns an empty list if no files were found.

           Names can be specified in a variety of platform independent forms.
           Any names in the form -lname are converted into libname.*, where .*
           is an appropriate suffix for the platform.

       bootstrap()
           Syntax:

           bootstrap($module [...])

           This is the normal entry point for automatic dynamic loading in
           Perl.

           It performs the following actions:

           ·       locates an auto/$module directory by searching @INC

           ·       uses dl_findfile() to determine the filename to load


so this relies on libtool creating the file and calling it
"mummer.so.0" or similar. That's reasonably likely; I was being safe
because I figured that libtool added the "dlname" line to the *.la
file for a reason, for example:

# The name that we can dlopen(3).
dlname='mummer.so.0'


> In other words, for testing, I would rather use the Perl code that is
> generated by SWIG and that will ultimately will be installed, rather than
> having to write my own loader. So far it seems to work by only tweaking the
> environment with only the name ".libs" being really hard coded here. The
> name of the library is coming from the Makefile.am (perl5/mummer.la).

There are two library files, the *.la file and the actual file that is
dlopen'd, which could be a *.so file.

Does SWIG know anything about libtool?

Maybe you could ask on the libtool mailing list whether you can rely
on the library file being placed in .libs.