NAME
h2xs - convert .h C header files to Perl extensions
SYNOPSIS
hh22xxss [OOPPTTIIOONNSS ...] [headerfile ... [extralibraries]]hh22xxss -hh|-??|--hheellpp
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 modulename will be used for the name of the extension. If mod-
ulename 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 extralibraries 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 augmentedby including arguments of the form -LL//aannootthheerr//lliibbrraarryy//ppaatthh in the
extra-libraries argument.
OOPPTTIIOONNSS-AA, --oommiitt-aauuttoollooaadd
Omit all autoload facilities. This is the same as -cc but also
removes the "use AutoLoader" statement from the .pm file.-BB, --bbeettaa-vveerrssiioonn
Use an alpha/beta style version number. Causes version number tobe "0.0001" unless -vv is specified.
-CC, --oommiitt-cchhaannggeess
Omits creation of the Changes file, and adds a HISTORY section to the POD template.-FF, --ccpppp-ffllaaggss=addflags
Additional flags to specify to C preprocessor when scanning header for function declarations. Writes these options in the generated Makefile.PL too.-MM, --ffuunncc-mmaasskk=regular expression
selects functions/macros to process.-OO, --oovveerrwwrriittee-ookk
Allows a pre-existing extension directory to be overwritten.
-PP, --oommiitt-ppoodd
Omit the autogenerated stub POD section.-XX, --oommiitt-XXSS
Omit the XS portion. Used to generate templates for a modulewhich is not XS-based. "-c" and "-f" are implicitly enabled.
-aa, --ggeenn-aacccceessssoorrss
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; addi-
tionally two methods are constructed for the structure type itself, "toptr" which returns a Ptr type pointing to the samestructure, and a "new" method to construct and return a new struc-
ture, initialised to zeroes.-bb, --ccoommppaatt-vveerrssiioonn=version
Generates a .pm file which is backwards compatible with the speci-
fied 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 perlyou 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.
-cc, --oommiitt-ccoonnssttaanntt
Omit "constant()" from the .xs file and corresponding specialised "AUTOLOAD" from the .pm file.-dd, --ddeebbuuggggiinngg
Turn on debugging messages.-ee, --oommiitt-eennuummss=[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 regularexpression 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.-ff, --ffoorrccee
Allows an extension to be created for a header even if that header is not found in standard include directories.-gg, --gglloobbaall
Include code for safely storing static data in the .xs file. Extensions that do no make use of static data can ignore this option.-hh, -??, --hheellpp
Print the usage, help and version for this h2xs and exit.
-kk, --oommiitt-ccoonnsstt-ffuunncc
For function arguments declared as "const", omit the const attribute in the generated XS code.-mm, --ggeenn-ttiieedd-vvaarr
EExxppeerriimmeennttaall: for each variable declared in the header file(s), declare a perl variable of the same name magically tied to the C variable.-nn, --nnaammee=modulename
Specifies a name to be used for the extension, e.g., -n RPC::DCE
-oo, --ooppaaqquuee-rree=regular expression
Use "opaque" data type for the C types matched by the regularexpression, even if these types are "typedef"-equivalent to types
from typemaps. Should not be used without -xx.
This may be useful since, say, types which are "typedef"-equiva-
lent to integers may represent OS-related handles, and one may
want to work with these handles in OO-way, as in "$han-
dle->dosomething()". 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).-pp, --rreemmoovvee-pprreeffiixx=prefix
Specify a prefix which should be removed from the Perl functionnames, e.g., -p secrgy This sets up the XS PPRREEFFIIXX keyword and
removes the prefix from functions that are autoloaded via the "constant()" mechanism.-ss, --ccoonnsstt-ssuubbss=sub1,sub2
Create a perl subroutine for the specified macros rather than autoload with the constant() subroutine. These macros are assumedto have a return type of cchhaarr **, e.g., -s secrgywild-
cardname,secrgywildcardsid.-tt, --ddeeffaauulltt-ttyyppee=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 havethis type. Future versions of "h2xs" may gain the ability to make
educated guesses.--uussee-nneeww-tteessttss
When --ccoommppaatt-vveerrssiioonn (-bb) 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 PREREQPM in the generated "Makefile.PL".--uussee-oolldd-tteessttss
Will force the generation of test code that uses the older "Test" module.--sskkiipp-eexxppoorrtteerr
Do not use "Exporter" and/or export any symbol.--sskkiipp-ppppppoorrtt
Do not use "Devel::PPPort": no portability to older version.--sskkiipp-aauuttoollooaaddeerr
Do not use the module "AutoLoader"; but keep the constant() func-
tion and "sub AUTOLOAD" for constants.--sskkiipp-ssttrriicctt
Do not use the pragma "strict".--sskkiipp-wwaarrnniinnggss
Do not use the pragma "warnings".-vv, --vveerrssiioonn=version
Specify a version number for this extension. This version number is added to the templates. The default is 0.01, or 0.0001 if"-B" is specified. The version specified should be numeric.
-xx, --aauuttooggeenn-xxssuubbss
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 looklike "NAME1,NAME2". In this case NAME1 is used instead of the
specified string, but XSUBs are emitted only for the declarationsincluded from file NAME2.
Note that some types of arguments/return-values for functions may
result in XSUB-declarations/typemap-entries which need hand-edit-
ing. Such may be objects which cannot be converted from/to a pointer (like "long long"), pointers to functions, or arrays. Seealso the section on "LIMITATIONS of -xx".
EEXXAAMMPPLLEESS# Default behavior, extension is Rusers
h2xs rpcsvc/rusers
# Same, but extension is RUSERS
h2xs -n RUSERS rpcsvc/rusers
# Extension is rpcsvc::rusers. Still finds
h2xs rpcsvc::rusers
# Extension is ONC::RPC. Still finds
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 Lib::Foo which works at least with Perl5.00503.
# 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 Perl5.00503.
# 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 "secrgy" is dropped from perl function names
h2xs -n DCE::rgynbase -p secrgy dce/rgynbase
# Extension is DCE::rgynbase
# prefix "secrgy" is dropped from perl function names
# subroutines are created for secrgywildcardname and
# secrgywildcardsid
h2xs -n DCE::rgynbase -p secrgy \
-s secrgywildcardname,secrgywildcardsid 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
EExxtteennssiioonn bbaasseedd oonn .h aanndd .c ffiilleess Suppose that you have some C files implementing some functionality, and the corresponding header files. How to create an extension which makes this functionality accessable in Perl? The example below assumes that the header files are interfacesimple.h and interfacehairy.h, and youwant the perl module be named as "Ext::Ension". If you need some pre-
processor directives and/or linking with external libraries, see theflags "-F", "-L" and "-l" in "OPTIONS".
Find the directory nameStart 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 extensionRun h2xs, overwriting older autogenerated files:
h2xs -Oxan Ext::Ension interfacesimple.h interfacehairy.h
h2xs looks for header files after changing to the extension direc-
tory, 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 youdecide 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 inventbetter interfaces than what h2xs could guess.
Consider this section as a guideline only, some other options ofh2xs may better suit your needs.
ENVIRONMENT No environment variables are used. AUTHOR Larry Wall and othersSEE ALSO
perl, perlxstut, ExtUtils::MakeMaker, and AutoLoader. DIAGNOSTICS The usual warnings if it cannot read or write the files involved.LLIIMMIITTAATTIIOONNSS ooff -xx
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 parame-
ter. 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 myfoo(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.perl v5.8.6 2009-01-12 H2XS(1)