h2xs
convert .h C header files to Perl extensions
Synopsis
h2xs [
OPTIONS ...] [headerfile ...
[extra_libraries]]
h2xs
-h|-?|--help
add an example, a script, a trick and tips
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
# Extension is a pure Perl module with no XS code.
h2xs -X My::Module
# Extension is Lib::Foo which works at least with Perl5.005_03.
# Constants are created for all #defines and enums h2xs can find
# in foo.h.
h2xs -b 5.5.3 -n Lib::Foo foo.h
# Extension is Lib::Foo which works at least with Perl5.005_03.
# Constants are created for all #defines but only for enums
# whose names do not start with 'bar_'.
h2xs -b 5.5.3 -e '^bar_' -n Lib::Foo foo.h
# 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
# Make XS without defines in perl.h, but with function declarations
# visible from perl.h. Name of the extension is perl1.
# When scanning perl.h, define -DEXT=extern -DdEXT= -DINIT(x)=
# Extra backslashes below because the string is passed to shell.
# Note that a directory with perl header files would
# be added automatically to include path.
h2xs -xAn perl1 -F "-DEXT=extern -DdEXT= -DINIT\(x\)=" perl.h
# 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
functionality, and the corresponding header files. How to create
an extension which makes this functionality accessible 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
make test
Hints
It is important to do "make dist" as early as possible.
This way you can easily merge(1) your changes to
autogenerated files if you decide to edit your ".h"
files and rerun h2xs.
Do not forget to edit the documentation in the generated
.pm file.
Consider the autogenerated files as skeletons only, you may
invent better interfaces than what h2xs could guess.
Consider this section as a guideline only, some other options of
h2xs may better suit your needs.
source
* Added IO::CaptureOutput to PREREQ_PM
YVDHOVE::System v1.01
* original version; created by
h2xs 1.23 with options '-AXc -n
YVDHOVE::System'
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
extension. 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.
In spite of its
name, h2xs may also be used to create a skeleton pure
Perl module. See the -X option.
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 version number to be "0.00_01"
unless -v is specified.
-C,
--omit-changes
Omits creation of the
Changes file, and adds a HISTORY
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 overwritten.
-P,
--omit-pod
Omit the autogenerated stub
POD section.
-X,
--omit-XS
Omit the XS
portion. Used to generate a skeleton pure Perl module.
"-c" and
"-f" are implicitly enabled.
-a,
--gen-accessors
Generate an accessor method for
each element of structs and unions. The generated methods
are named after the element name; will return the current
value of the element if called without additional arguments;
and will set the element to the supplied value (and return
the new value) if called with an additional argument.
Embedded structures and unions are returned as a pointer
rather than the complete structure, 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 compatibility 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.
-e,
--omit-enums=[regular
expression]
If regular expression is
not given, skip all constants that are defined in a C
enumeration. Otherwise skip only those constants that are
defined in an enum whose name matches regular
expression.
Since
regular expression is optional, make sure that this
switch is followed by at least one other switch if you omit
regular expression and have some pending arguments
such as header-file names. This is ok:
h2xs -e -n Module::Foo foo.h
This is not
ok:
h2xs -n Module::Foo -e foo.h
In the latter,
foo.h is taken as regular expression.
-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
Experimental: for each
variable declared in the header file(s), declare a perl
variable of the same name magically tied to the C
variable.
-n,
--name=module_name
Specifies a name to be used for
the extension, e.g., -n
RPC::DCE
-o,
--opaque-re=regular
expression
Use "opaque" data
type for the C types matched by the regular expression, even
if these types are
"typedef"-equivalent to types from
typemaps. Should not be used without -x.
This may be
useful since, say, types which are
"typedef"-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_wildcard_sid.
-t,
--default-type=type
Specify the internal type that
the constant() mechanism 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 5.6.2. "Test::More" will be added
to PREREQ_PM in the generated
"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
Do not use the module
"AutoLoader"; but keep the
constant() function and "sub
AUTOLOAD" for constants.
--skip-strict
Do not use the pragma
"strict".
--skip-warnings
Do not use the pragma
"warnings".
-v,
--version=version
Specify a version number for
this extension. This version number is added to the
templates. The default is 0.01, or 0.00_01 if
"-B" is specified. The version
specified should be numeric.
-x,
--autogen-xsubs
Automatically generate XSUBs
basing on function declarations 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 declarations
included from file NAME2 .
Note that some
types of arguments/return-values for functions may
result in XSUB-declarations/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".
diagnostics
The usual warnings if it cannot read or write the files involved.
environment
No environment variables are used.
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, argument
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;
CODE:
s = SvPV(sv,len);
RETVAL = foo(s, len);
OUTPUT:
RETVAL
or alternately
static int
my_foo(SV *sv)
STRLEN len;
char *s = SvPV(sv,len);
return foo(s, len);
MODULE = foo PACKAGE = foo PREFIX = my_
int
foo(sv)
SV *sv
See perlxs and perlxstut for additional details.
see also
perl,
perlxstut, ExtUtils::MakeMaker, and AutoLoader.
author
Larry Wall and
others