Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
ExtUtils::Constant(3)  Perl Programmers	Reference Guide	 ExtUtils::Constant(3)

NAME
       ExtUtils::Constant - generate XS	code to	import C header	constants

SYNOPSIS
	   use ExtUtils::Constant qw (WriteConstants);
	   WriteConstants(
	       NAME => 'Foo',
	       NAMES =>	[qw(FOO	BAR BAZ)],
	   );
	   # Generates wrapper code to make the	values of the constants	FOO BAR	BAZ
	   #  available	to perl

DESCRIPTION
       ExtUtils::Constant facilitates generating C and XS wrapper code to
       allow perl modules to AUTOLOAD constants	defined	in C library header
       files.  It is principally used by the "h2xs" utility, on	which this
       code is based.  It doesn't contain the routines to scan header files to
       extract these constants.

USAGE
       Generally one only needs	to call	the "WriteConstants" function, and
       then

	   #include "const-c.inc"

       in the C	section	of "Foo.xs"

	   INCLUDE: const-xs.inc

       in the XS section of "Foo.xs".

       For greater flexibility use "constant_types()", "C_constant" and
       "XS_constant", with which "WriteConstants" is implemented.

       Currently this module understands the following types. h2xs may only
       know a subset. The sizes	of the numeric types are chosen	by the
       "Configure" script at compile time.

       IV  signed integer, at least 32 bits.

       UV  unsigned integer, the same size as IV

       NV  floating point type,	probably "double", possibly "long double"

       PV  NUL terminated string, length will be determined with "strlen"

       PVN A fixed length thing, given as a [pointer, length] pair. If you
	   know	the length of a	string at compile time you may use this
	   instead of PV

       SV  A mortal SV.

       YES Truth.  ("PL_sv_yes")  The value is not needed (and ignored).

       NO  Defined Falsehood.  ("PL_sv_no")  The value is not needed (and
	   ignored).

       UNDEF
	   "undef".  The value of the macro is not needed.

FUNCTIONS
       constant_types
	   A function returning	a single scalar	with "#define" definitions for
	   the constants used internally between the generated C and XS
	   functions.

       XS_constant PACKAGE, TYPES, XS_SUBNAME, C_SUBNAME
	   A function to generate the XS code to implement the perl subroutine
	   PACKAGE::constant used by PACKAGE::AUTOLOAD to load constants.
	   This	XS code	is a wrapper around a C	subroutine usually generated
	   by "C_constant", and	usually	named "constant".

	   TYPES should	be given either	as a comma separated list of types
	   that	the C subroutine "constant" will generate or as	a reference to
	   a hash. It should be	the same list of types as "C_constant" was
	   given.  [Otherwise "XS_constant" and	"C_constant" may have
	   different ideas about the number of parameters passed to the	C
	   function "constant"]

	   You can call	the perl visible subroutine something other than
	   "constant" if you give the parameter	XS_SUBNAME. The	C subroutine
	   it calls defaults to	the name of the	perl visible subroutine,
	   unless you give the parameter C_SUBNAME.

       autoload	PACKAGE, VERSION, AUTOLOADER
	   A function to generate the AUTOLOAD subroutine for the module
	   PACKAGE VERSION is the perl version the code	should be backwards
	   compatible with.  It	defaults to the	version	of perl	running	the
	   subroutine.	If AUTOLOADER is true, the AUTOLOAD subroutine falls
	   back	on AutoLoader::AUTOLOAD	for all	names that the constant()
	   routine doesn't recognise.

       WriteMakefileSnippet
	   WriteMakefileSnippet	ATTRIBUTE => VALUE [, ...]

	   A function to generate perl code for	Makefile.PL that will
	   regenerate the constant subroutines.	 Parameters are	named as
	   passed to "WriteConstants", with the	addition of "INDENT" to
	   specify the number of leading spaces	(default 2).

	   Currently only "INDENT", "NAME", "DEFAULT_TYPE", "NAMES", "C_FILE"
	   and "XS_FILE" are recognised.

       WriteConstants ATTRIBUTE	=> VALUE [, ...]
	   Writes a file of C code and a file of XS code which you should
	   "#include" and "INCLUDE" in the C and XS sections respectively of
	   your	module's XS code.  You probably	want to	do this	in your
	   "Makefile.PL", so that you can easily edit the list of constants
	   without touching the	rest of	your module.  The attributes supported
	   are

	   NAME
	       Name of the module.  This must be specified

	   DEFAULT_TYPE
	       The default type	for the	constants.  If not specified "IV" is
	       assumed.

	   BREAKOUT_AT
	       The names of the	constants are grouped by length.  Generate
	       child subroutines for each group	with this number or more names
	       in.

	   NAMES
	       An array	of constants' names, either scalars containing names,
	       or hashrefs as detailed in "C_constant".

	   PROXYSUBS
	       If true,	uses proxy subs. See ExtUtils::Constant::ProxySubs.

	   C_FH
	       A filehandle to write the C code	to.  If	not given, then	C_FILE
	       is opened for writing.

	   C_FILE
	       The name	of the file to write containing	the C code.  The
	       default is "const-c.inc".  The "-" in the name ensures that the
	       file can't be mistaken for anything related to a	legitimate
	       perl package name, and not naming the file ".c" avoids having
	       to override Makefile.PL's ".xs" to ".c" rules.

	   XS_FH
	       A filehandle to write the XS code to.  If not given, then
	       XS_FILE is opened for writing.

	   XS_FILE
	       The name	of the file to write containing	the XS code.  The
	       default is "const-xs.inc".

	   XS_SUBNAME
	       The perl	visible	name of	the XS subroutine generated which will
	       return the constants. The default is "constant".

	   C_SUBNAME
	       The name	of the C subroutine generated which will return	the
	       constants.  The default is XS_SUBNAME.  Child subroutines have
	       "_" and the name	length appended, so constants with 10
	       character names would be	in "constant_10" with the default
	       XS_SUBNAME.

AUTHOR
       Nicholas	Clark <nick@ccl4.org> based on the code	in "h2xs" by Larry
       Wall and	others

perl v5.32.0			  2020-06-14		 ExtUtils::Constant(3)

NAME | SYNOPSIS | DESCRIPTION | USAGE | FUNCTIONS | AUTHOR

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=ExtUtils::Constant&sektion=3&manpath=FreeBSD+12.2-RELEASE+and+Ports>

home | help