using XS with C++

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

Hi. My question concerns how one defines in XS that one has a C++ class. The only docs I can find on the subject of using XS with C++ is in the XS reference manual so I am trying to run their example but it is failing on "make" and the error indicates that the compiler is not recognizing the language as C++, so it doesn't recognize the class. This would make sense since it is compiling a .c file, namely myclass.c. I am confused. No matter what I do, it seems that xsubpp generates a .c file and never a .cc file. But if this is the case, then how will it ever recognize class declarations? Or is it saying that I have not supplied a class definition? What am I missing? Here's the output of "make":

cc -c   -O     -DVERSION=\"0.01\"  -DXS_VERSION=\"0.01\" -Kpic -I/usr/
+local/lib/
perl5/sun4-solaris/5.00405/CORE  myclass.c
"/home/judyf/perlwork/myclass/myclass.h", line 9: undefined or not a t
+ype: class
"/home/judyf/perlwork/myclass/myclass.h", line 9: syntax error before 
+or at: col
or
"/home/judyf/perlwork/myclass/myclass.h", line 9: undefined or not a t
+ype: color
"/home/judyf/perlwork/myclass/myclass.h", line 15: syntax error before
+ or at: /
"/home/judyf/perlwork/myclass/myclass.h", line 23: syntax error before
+ or at: in
t
"/home/judyf/perlwork/myclass/myclass.h", line 24: cannot recover from
+ previous
errors
cc: acomp failed for myclass.c
*** Error code 2
make: Fatal error: Command failed for target `myclass.o'
[download]

Here's the class declaration from the myclass.h file:

class  color {
        public:
        color();
        ~color();
        int blue();
        int set_blue( int );

        private:
        int c_blue;
};
[download]

Here's the relevant .xs code:

int
color::blue()

void
color::set_blue( val )
        int val
[download]

My instinct would be, in the myclass.xs file, to create a new package within the one module (called "color") but based on the reference manual doc, I refrained from doing this and kept the class method declaration under the one package (with same name as module). hence, in myclass.xs:

MODULE = myclass                PACKAGE = myclass
[download]

Here's the relevant portion of typemap file:

color *                 O_OBJECT

OUTPUT
# The Perl object is blessed into 'CLASS', which should be a
# char* having the name of the package for the blessing.
O_OBJECT
        sv_setref_pv( $arg, CLASS, (void*)$var );

INPUT
O_OBJECT
        if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) )
                $var = ($type)SvIV((SV*)SvRV( $arg ));
        else{
                warn( \"${Package}::$func_name() -- $var is not a bles
+sed SV ref
erence\" );
                XSRETURN_UNDEF;
        }
[download]

Here's Makefile.PL (where I set 'XSOPT' to tell it I'm using C++):

use ExtUtils::MakeMaker;
WriteMakefile(
    'NAME'      => 'myclass',
    'VERSION_FROM' => 'myclass.pm', # finds $VERSION
    'LIBS'      => [''],   # e.g., '-lm'
    'DEFINE'    => '',     # e.g., '-DHAVE_SOMETHING'
    'INC'       => '',     # e.g., '-I/usr/include/other'
    'XSOPT'     => '-C++',
);
[download]

Thanks for your help.

Comment on using XS with C++ Select or Download Code

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Re: using XS with C++ by qi3ber (Scribe) on Jul 21, 2000 at 19:32 UTC
I haven't tried this myself, but what you need to do to get this to go, is add another entry to your WriteMakefile() call, it should look like this: `WriteMakefile( 'NAME' => 'myclass', 'VERSION_FROM' => 'myclass.pm', # finds $VERSION 'LIBS' => [''], # e.g., '-lm' 'DEFINE' => '', # e.g., '-DHAVE_SOMETHING' 'INC' => '', # e.g., '-I/usr/include/other' 'XSOPT' => '-C++', 'XS' => {'myclass.xs' => 'myclass.cc'}, );` [download] And you might need to add another line requesting that it clean up the .cc file when a make clean is run. The man page is a bit sketchy on that point, so the extra line you might need to add will look like this: `'clean' => {FILES => "*.cc"}` [download]	[reply] [d/l] [select]
RE: Re: using XS with C++ by juda (Initiate) on Jul 21, 2000 at 21:57 UTC
Thanks. I tried what you suggested. One problem is that the Makefile is still setting CC = cc so it still tries to compile with the C compiler. Here's the output: judyf: betaman.portsoft.com.138> make mkdir ./blib mkdir ./blib/lib mkdir ./blib/arch mkdir ./blib/arch/auto mkdir ./blib/arch/auto/myclass mkdir ./blib/lib/auto mkdir ./blib/lib/auto/myclass mkdir ./blib/man3 cp myclass.pm ./blib/lib/myclass.pm AutoSplitting ./blib/lib/myclass.pm (./blib/lib/auto/myc cc -c -O -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" perl5/sun4-solaris/5.00405/CORE myclass.cc cc: No input file specified, no output generated *** Error code 1 make: Fatal error: Command failed for target `myclass.o' [download] I did an 'ls' and it turns out that myclass.cc does not exist. Neither does myclass.c for that matter. Then, I took out the line: 'XS' => {'myclass.xs' => 'myclass.cc'}, in Makefile.PL. Then did a 'make clean' and reran ' perl Makefile.PL', then 'make'. Here's the output: <CODE> judyf: betaman.portsoft.com.138> make mkdir ./blib mkdir ./blib/lib mkdir ./blib/arch mkdir ./blib/arch/auto mkdir ./blib/arch/auto/myclass mkdir ./blib/lib/auto mkdir ./blib/lib/auto/myclassmkdir ./blib/man3 cp myclass.pm ./blib/lib/myclass.pm AutoSplitting ./blib/lib/myclass.pm (./blib/lib/auto/myclass) /bin/perl -I/usr/local/lib/perl5/sun4-solaris/5.00405 -I/usr/local/lib +/perl5 /us r/local/lib/perl5/ExtUtils/xsubpp -C++ -typemap /usr/local/lib/perl5/ +ExtUtils/t ypemap -typemap typemap myclass.xs >myclass.tc && mv myclass.tc myclas +s.c Please specify prototyping behavior for myclass.xs (see perlxs manual) cc -c -O -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" -Kpic -I/usr/ +local/lib/ perl5/sun4-solaris/5.00405/CORE myclass.c "/home/judyf/perlwork/myclass/myclass.h", line 9: undefined or not a type: class ... (and so on with rest of errors) [download] Not sure why it's missing these lines in Makefile when it's in C++ mode. Also, I edited Makefile and these lines are still set to: <CODE> CC = cc LD = cc <CODE> I'll keep looking into it but if you have any further suggestions, I'm all ears. Thanks.	[reply] [d/l] [select]
RE: RE: Re: using XS with C++ by tye (Sage) on Jul 22, 2000 at 07:43 UTC
I'm pretty sure that the `XSOPT=>'-C++'` option is only partially implemented. It only does (at most) one of something like 3 things that it should do. Now, I think the direction C and C++ compilers have moved is that you use "cc" to compile both C and C++ files and the compiler determines what type of code it is compiling by whether the file name ends in .c or one of .cc, .cpp, .c++, .cxx, etc., where each compiler recognizes about two different extensions for C++ code. So the `CC=cc` is probably not a problem. The problem is that it is generating a file named myclass.c instead of myclass.cxx. I managed to use C++ in XS as part of some other strange work I was doing (see the latest versions of Win32API::File, for example). I used .cxx and wrote my own rules out with `sub MY::postamble`. At least the latest MakeMaker knows how to compile a .cxx file if you ask it to.	[reply] [d/l] [select]