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Re: Building cpan module that links with proprietary libs

Hi Andrew,

On Thu, May 29, 2014 at 4:12 AM, Andrew DeFaria  wrote:
> I'm attempting to build a cpan module (well actually it's not a cpan module
> but rather a module that uses MakeMaker and has the familiar perl
> Makefile.PL, make, make test, make install installation procedure.
> Additionally I need to link it to a set of proprietary libs that I am given
> only the .lib files for. If you must know this is for Perforce's P4Perl
> which I'd like to get working with Cygwin's Perl natively.
> I download the P4API bundle (the package that has include files and the .lib
> files pre-compiled).

The C++ P4 API is platform-specific; which platform did you choose?
If it really contains .lib files (not .a), those are not recognized by
Cygwin's gcc.

> Next I need to do:
> $ perl Makefile.PL --api-dir /.../path/to/unzipped/p4api
> This works fine and I procedure with the make. This fails with things like:
> make[1]: Leaving directory '/cygdrive/a/perl/P4Perl.Cygwin/lib'
> g++ -c  -I/cygdrive/a/perl/ -Ilib -x c++
> -DUSEIMPORTLIB -O3   -DVERSION=\"2014.1\" -DXS_VERSION=\"2014.1\"
> "-I/usr/lib/perl5/5.14/x86_64-cygwin-threads/CORE"
> -DID_OS="\"CYGWIN17THREAD\"" -DID_REL="\"2014.1\"" -DID_PATCH="\"842847\""
> -DID_Y="\"2014\"" -DID_M="\"05\"" -DID_D="\"06\"" -DOS_CYGWIN -DOS_CYGWIN17
> -DID_API="\"2014.1/821990\"" P4.c
> Running Mkbootstrap for P4 ()
> chmod 644
> rm -f blib/arch/auto/P4/P4.dll
> g++  -shared P4.o  -o blib/arch/auto/P4/P4.dll lib/libp4.a      \
>   /usr/lib/perl5/5.14/x86_64-cygwin-threads/CORE/cygperl5_14.dll        \
> P4.o:P4.c:(.text+0x45ac): undefined reference to `ClientApi::SetClient(char
> const*)'
> P4.o:P4.c:(.text+0x45ac): relocation truncated to fit: R_X86_64_PC32 against
> undefined symbol `ClientApi::SetClient(char const*)'
> P4.o:P4.c:(.text+0x4a9c): undefined reference to `ClientApi::SetHost(char
> const*)'
> Notice that it removes P4.dll, so it seems to know it's working with dll's,
> but then it calls g++ with a -o for libp4.a!

No it doesn't. The argument to -o is blib/arch/auto/P4/P4.dll
lib/libp4.a is the next input file. What does the following say?

nm lib/libp4.a | c++filt

> Meantime it fails with many undefined references. I think I might need to do
> perl Makefile.PL with other opts to tell it that while it's using Cygwin and
> can be very Linux-like, it needs to produce .dll's and not .a's or .o's.

It seems to be on the right track; "g++ -shared -o P4.dll" sounds good to me.

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The Tao of math: The numbers you can count are not the real numbers.
Life is complex, with real and imaginary parts.
"Ok, it boots. Which means it must be bug-free and perfect. " -- Linus Torvalds
"People disagree with me. I just ignore them." -- Linus Torvalds

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