llancet has asked for the wisdom of the Perl Monks concerning the following question:

I'm writing a module with XS and C++. After tried XSPP, I found it lack some important functions such as "PPCODE", so I decided to write XS code by my hand.

Though that, the Module::Build::WithXSpp is still very handful, as it automatically find and set C++ flags to compilers, and it calls TypeMap modules automatically. However, when I masked my .xsp files and set up my .xs files, the builder failed to build them into a single .so file. Instead, it compiles the code generated from my .xs files into blib/arch/auto/xs/XXX, and the code automatically generated by M::B::WithXSpp into blib/arch/auto/XXX.

......
cc -shared -L/usr/local/lib -fstack-protector -o blib/arch/auto/xs/Gen
+oEye_Page/GenoEye_Page.so xs/GenoEye_Page.o -lcairo -lstdc++ -lGenoEy
+e -lboost_regex
......
cc -shared -L/usr/local/lib -fstack-protector -o blib/arch/auto/GenoEy
+e/GenoEye.so buildtmp/GenoEye.o -lcairo -lstdc++ -lGenoEye -lboost_re
+gex

[download]

As a result, the generated .so file under the correct location is a null one. how could this happen?

This is the layout of my project: 
Build  Build.PL  Changes  ignore.txt  MANIFEST
MANIFEST.skip  MYMETA.json  MYMETA.yml  README

lib:
GenoEye.pm

src:
ppport.h

t:
00-load.t  01-page.t  boilerplate.t
manifest.t  pod-coverage.t  pod.t

xs:
GenoEye_Page.c  GenoEye_Page.o
GenoEye_Page.xs  typemap.map

[download]
Thanks!!

Replies are listed 'Best First'.
Re: Module::Build::WithXSpp does not correctly handle XS files correctly?
by Anonymous Monk on Jan 09, 2014 at 16:18 UTC
[reply]
[d/l]
      First, to use PPCODE, Wx embeds pure XS in "{% %}". So why don't I write XS code directly?

      Second, Wx use ExtUtils::MakeMaker, but not M::B or M::B::WithXSpp.
[reply]

        First, to use PPCODE, Wx embeds pure XS in "{% %}". So why don't I write XS code directly?

        Because xspp saves you typing because it is "thin" layer over xs?

        Second, Wx use ExtUtils::MakeMaker, but not M::B or M::B::WithXSpp.

        I don't see how this matters, both call INCLUDE_COMMAND...xspp... which works exactly the same way in both versions

[reply]
Re: Module::Build::WithXSpp does not correctly handle XS files correctly? ( module_name.xs )
by Anonymous Monk on Jan 10, 2014 at 11:13 UTC

    ok, I'm back and caffeinated :) If you go to http://p3rl.org/Module::Build::WithXSpp and look at https://metacpan.org/pod/Module::Build::WithXSpp#FEATURES-AND-CONVENTIONS it says

    By default, Module::Build::WithXSpp will automatically generate a main XS file for your module which includes all XS++ files and does the correct incantations to support C++.

    If Module::Build::WithXSpp detects any XS files in your module, it will skip the generation of this default file and assume that you wrote a custom main XS file.

    So I think that answers that

    If you go to https://metacpan.org/pod/Module::Build::WithXSpp#JUMP-START-FOR-THE-IMPATIENT it describes the expected layout

    So if your module_name is GenoEye (GenoEye.pm) and you have some .xs files (GenoEye_Page.xs) but you don't have GenoEye.xs, then GenoEye.xs (module_name.xs) won't be generated for you (because of GenoEye_Page.xs)

    So what you're missing is a GenoEye.xs (module_name.xs) which you need to create , something like WithIntAndString.xs something that uses

    INCLUDE_COMMAND: $^X -S xsubpp -- GenoEye_Page.xs

    I prefer running examples to reading docs, easier to figure out what docs to read instead of reading all the docs

[reply]
      I looked at the source code of M::B::WithXSpp, and it indeed has a bug. In function ACTION_generate_main_xs: 
      ...
  if (keys(%$xs_files) > 1) {
    # user knows what she's doing, do not generate XS
    $self->log_info("Found custom XS files. Not auto-generating main X
+S file...\n");
    return 1;
  }
...

      [download]

      The HashRef $xs_files contain all user-write XS files, but also contain the auto generated buildtmp/main.xs. And, it tests whether there are more than 1 xs files. This logic causes two issues:

      1. If I have only one manually-written XS file, the builder will still auto-generate the main.xs, which is not the expected behavior.

      2. If I run the builder, it will generate a main.xs. Thus the builder's behavior will change unexpectedly, as now the XS file amount is changed.

      This logic should be revised, and it looks like the plain XS support of M::B::WithXSpp is not extensively tested. Where can I report this issue?

[reply]
[d/l]
[reply]
Re: Module::Build::WithXSpp does not correctly handle XS files correctly?
by bulk88 (Priest) on Jan 09, 2014 at 23:48 UTC
    If you were using EUMM, i'd say try putting ".o" files into OBJECT key name for WriteMakefile, but you are not using EUMM. You can also try #xs room on irc.perl.org.
[reply]

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