SYNOPSIS

       h2xs [OPTIONS ...] [headerfile ... [extra_libraries]]

       h2xs -h|-?|--help


DESCRIPTION

       h2xs builds a Perl extension from C header files.  The
       extension will include functions which can be used to
       retrieve the value of any #define statement which was in
       the C header files.

       The module_name will be used for the name of the exten­
       sion.  If module_name is not supplied then the name of the
       first header file will be used, with the first character
       capitalized.

       If the extension might need extra libraries, they should
       be included here.  The extension Makefile.PL will take
       care of checking whether the libraries actually exist and
       how they should be loaded.  The extra libraries should be
       specified in the form -lm -lposix, etc, just as on the cc
       command line.  By default, the Makefile.PL will search
       through the library path determined by Configure.  That
       path can be augmented by including arguments of the form
       -L/another/library/path in the extra-libraries argument.


OPTIONS

       -A, --omit-autoload
            Omit all autoload facilities.  This is the same as -c
            but also removes the "use AutoLoader" statement from
            the .pm file.

       -B, --beta-version
            Use an alpha/beta style version number.  Causes ver­
            sion number to be "0.00_01" unless -v is specified.

       -C, --omit-changes
            Omits creation of the Changes file, and adds a HIS­
            TORY section to the POD template.

       -F, --cpp-flags=addflags
            Additional flags to specify to C preprocessor when
            scanning header for function declarations.  Writes
            these options in the generated Makefile.PL too.

       -M, --func-mask=regular expression
            selects functions/macros to process.

       -O, --overwrite-ok
            Allows a pre-existing extension directory to be over­
            written.

            (and return the new value) if called with an addi­
            tional argument. Embedded structures and unions are
            returned as a pointer rather than the complete struc­
            ture, to facilitate chained calls.

            These methods all apply to the Ptr type for the
            structure; additionally two methods are constructed
            for the structure type itself, "_to_ptr" which
            returns a Ptr type pointing to the same structure,
            and a "new" method to construct and return a new
            structure, initialised to zeroes.

       -b, --compat-version=version
            Generates a .pm file which is backwards compatible
            with the specified perl version.

            For versions < 5.6.0, the changes are.
                - no use of 'our' (uses 'use vars' instead)
                - no 'use warnings'

            Specifying a compatibility version higher than the
            version of perl you are using to run h2xs will have
            no effect.  If unspecified h2xs will default to com­
            patibility with the version of perl you are using to
            run h2xs.

       -c, --omit-constant
            Omit "constant()" from the .xs file and corresponding
            specialised "AUTOLOAD" from the .pm file.

       -d, --debugging
            Turn on debugging messages.

       -f, --force
            Allows an extension to be created for a header even
            if that header is not found in standard include
            directories.

       -g, --global
            Include code for safely storing static data in the
            .xs file.  Extensions that do no make use of static
            data can ignore this option.

       -h, -?, --help
            Print the usage, help and version for this h2xs and
            exit.

       -k, --omit-const-func
            For function arguments declared as "const", omit the
            const attribute in the generated XS code.

       -m, --gen-tied-var
            This may be useful since, say, types which are "type­
            def"-equivalent to integers may represent OS-related
            handles, and one may want to work with these handles
            in OO-way, as in "$handle->do_something()".  Use "-o
            ." if you want to handle all the "typedef"ed types as
            opaque types.

            The type-to-match is whitewashed (except for commas,
            which have no whitespace before them, and multiple
            "*" which have no whitespace between them).

       -p, --remove-prefix=prefix
            Specify a prefix which should be removed from the
            Perl function names, e.g., -p sec_rgy_ This sets up
            the XS PREFIX keyword and removes the prefix from
            functions that are autoloaded via the "constant()"
            mechanism.

       -s, --const-subs=sub1,sub2
            Create a perl subroutine for the specified macros
            rather than autoload with the constant() subroutine.
            These macros are assumed to have a return type of
            char *, e.g., -s sec_rgy_wildcard_name,sec_rgy_wild­
            card_sid.

       -t, --default-type=type
            Specify the internal type that the constant() mecha­
            nism uses for macros.  The default is IV (signed
            integer).  Currently all macros found during the
            header scanning process will be assumed to have this
            type.  Future versions of "h2xs" may gain the ability
            to make educated guesses.

       --use-new-tests
            When --compat-version (-b) is present the generated
            tests will use "Test::More" rather than "Test" which
            is the default for versions before 5.7.2 .
            "Test::More" will be added to PREREQ_PM in the gener­
            ated "Makefile.PL".

       --use-old-tests
            Will force the generation of test code that uses the
            older "Test" module.

       --skip-exporter
            Do not use "Exporter" and/or export any symbol.

       --skip-ppport
            Do not use "Devel::PPPort": no portability to older
            version.

       --skip-autoloader

       -x, --autogen-xsubs
            Automatically generate XSUBs basing on function dec­
            larations in the header file.  The package "C::Scan"
            should be installed. If this option is specified, the
            name of the header file may look like "NAME1,NAME2".
            In this case NAME1 is used instead of the specified
            string, but XSUBs are emitted only for the declara­
            tions included from file NAME2.

            Note that some types of arguments/return-values for
            functions may result in XSUB-declara­
            tions/typemap-entries which need hand-editing. Such
            may be objects which cannot be converted from/to a
            pointer (like "long long"), pointers to functions, or
            arrays.  See also the section on "LIMITATIONS of -x".


EXAMPLES

               # Default behavior, extension is Rusers
               h2xs rpcsvc/rusers

               # Same, but extension is RUSERS
               h2xs -n RUSERS rpcsvc/rusers

               # Extension is rpcsvc::rusers. Still finds <rpcsvc/rusers.h>
               h2xs rpcsvc::rusers

               # Extension is ONC::RPC.  Still finds <rpcsvc/rusers.h>
               h2xs -n ONC::RPC rpcsvc/rusers

               # Without constant() or AUTOLOAD
               h2xs -c rpcsvc/rusers

               # Creates templates for an extension named RPC
               h2xs -cfn RPC

               # Extension is ONC::RPC.
               h2xs -cfn ONC::RPC

               # Makefile.PL will look for library -lrpc in
               # additional directory /opt/net/lib
               h2xs rpcsvc/rusers -L/opt/net/lib -lrpc

               # Extension is DCE::rgynbase
               # prefix "sec_rgy_" is dropped from perl function names
               h2xs -n DCE::rgynbase -p sec_rgy_ dce/rgynbase

               # Extension is DCE::rgynbase
               # prefix "sec_rgy_" is dropped from perl function names
               # subroutines are created for sec_rgy_wildcard_name and sec_rgy_wildcard_sid
               h2xs -n DCE::rgynbase -p sec_rgy_ \
               -s sec_rgy_wildcard_name,sec_rgy_wildcard_sid dce/rgynbase

               # Same with function declaration in proto.h as visible from perl.h.
               h2xs -xAn perl2 perl.h,proto.h

               # Same but select only functions which match /^av_/
               h2xs -M '^av_' -xAn perl2 perl.h,proto.h

               # Same but treat SV* etc as "opaque" types
               h2xs -o '^[S]V \*$' -M '^av_' -xAn perl2 perl.h,proto.h

       Extension based on .h and .c files

       Suppose that you have some C files implementing some func­
       tionality, and the corresponding header files.  How to
       create an extension which makes this functionality access­
       able in Perl?  The example below assumes that the header
       files are interface_simple.h and interface_hairy.h, and
       you want the perl module be named as "Ext::Ension".  If
       you need some preprocessor directives and/or linking with
       external libraries, see the flags "-F", "-L" and "-l" in
       "OPTIONS".

       Find the directory name
           Start with a dummy run of h2xs:

             h2xs -Afn Ext::Ension

           The only purpose of this step is to create the needed
           directories, and let you know the names of these
           directories.  From the output you can see that the
           directory for the extension is Ext/Ension.

       Copy C files
           Copy your header files and C files to this directory
           Ext/Ension.

       Create the extension
           Run h2xs, overwriting older autogenerated files:

             h2xs -Oxan Ext::Ension interface_simple.h interface_hairy.h

           h2xs looks for header files after changing to the
           extension directory, so it will find your header files
           OK.

       Archive and test
           As usual, run

             cd Ext/Ension
             perl Makefile.PL
             make dist
             make

           Consider this section as a guideline only, some other
           options of h2xs may better suit your needs.


ENVIRONMENT

       No environment variables are used.


AUTHOR

       Larry Wall and others


SEE ALSO

       perl, perlxstut, ExtUtils::MakeMaker, and AutoLoader.


DIAGNOSTICS

       The usual warnings if it cannot read or write the files
       involved.


LIMITATIONS of -x

       h2xs would not distinguish whether an argument to a C
       function which is of the form, say, "int *", is an input,
       output, or input/output parameter.  In particular, argu­
       ment declarations of the form

           int
           foo(n)
               int *n

       should be better rewritten as

           int
           foo(n)
               int &n

       if "n" is an input parameter.

       Additionally, h2xs has no facilities to intuit that a
       function

          int
          foo(addr,l)
               char *addr
               int   l

       takes a pair of address and length of data at this
       address, so it is better to rewrite this function as

           int
           foo(sv)
                   SV *addr
               PREINIT:
                   STRLEN len;
                   char *s;

               return foo(s, len);
           }

           MODULE = foo        PACKAGE = foo   PREFIX = my_

           int
           foo(sv)
               SV *sv

       See perlxs and perlxstut for additional details.



perl v5.8.0                 2003-03-13                    H2XS(1)

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