ExtUtils::Constant(3p) Perl Programmers Reference Guide

ExtUtils::Constant(3p) Perl Programmers Reference Guide #

ExtUtils::Constant(3p) Perl Programmers Reference Guide

NNAAMMEE #

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

SSYYNNOOPPSSIISS #

     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

DDEESSCCRRIIPPTTIIOONN #

 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.

UUSSAAGGEE #

 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 _I_V

 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 _P_V

 SV  A mmoorrttaall 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.

FFUUNNCCTTIIOONNSS #

 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
     _P_A_C_K_A_G_E::constant used by _P_A_C_K_A_G_E::AUTOLOAD to load constants.  This
     XS code is a wrapper around a C subroutine usually generated by
     "C_constant", and usually named "constant".

     _T_Y_P_E_S 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 _X_S___S_U_B_N_A_M_E. The C subroutine it
     calls defaults to the name of the perl visible subroutine, unless you
     give the parameter _C___S_U_B_N_A_M_E.

 autoload PACKAGE, VERSION, AUTOLOADER
     A function to generate the AUTOLOAD subroutine for the module _P_A_C_K_A_G_E
     _V_E_R_S_I_O_N is the perl version the code should be backwards compatible
     with.  It defaults to the version of perl running the subroutine.  If
     _A_U_T_O_L_O_A_D_E_R is true, the AUTOLOAD subroutine falls back on
     AutoLoader::AUTOLOAD for all names that the ccoonnssttaanntt(()) 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___F_I_L_E
         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 _X_S___F_I_L_E
         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 _X_S___S_U_B_N_A_M_E.  Child subroutines have
         "_" and the name length appended, so constants with 10 character
         names would be in "constant_10" with the default _X_S___S_U_B_N_A_M_E.

AAUUTTHHOORR #

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

perl v5.36.3 2019-02-13 ExtUtils::Constant(3p)