oracular (3) ExtUtils::Builder::Conf.3pm.gz
NAME
ExtUtils::Builder::Conf - Configure-time utilities for using C headers, libraries, or OS features
VERSION
version 0.020
SYNOPSIS
load_module("ExtUtils::Builder::Conf");
assert_compile_run(diag => 'no PF_MOONLASER', source => <<'EOF');
#include <stdio.h>
#include <sys/socket.h>
int main(int argc, char *argv[]) {
printf("PF_MOONLASER is %d\n", PF_MOONLASER);
return 0;
}
EOF
DESCRIPTION
Often Perl modules are written to wrap functionality found in existing C headers, libraries, or to use
OS-specific features. It is useful to check for the existance of these requirements before attempting to
actually build the module.
Objects in this class provide an extension around ExtUtils::Builder::Compiler to simplify the creation of
a .c file, compiling, linking and running it, to test if a certain feature is present.
It may also be necessary to search for the correct library to link against, or for the right include
directories to find header files in. This class also provides assistance here.
DELEGATES
try_compile_run
$success = try_compile_run(%args);
$success = try_compile_run($source);
Try to compile, link, and execute a C program whose source is given. Returns true if the program compiled
and linked, and exited successfully. Returns false if any of these steps fail.
Takes the following named arguments. If a single argument is given, that is taken as the source string.
source => STRING
The source code of the C program to try compiling, building, and running.
extra_compiler_flags => ARRAY
Optional. If specified, pass extra flags to the compiler.
extra_linker_flags => ARRAY
Optional. If specified, pass extra flags to the linker.
define => STRING
Optional. If specified, then the named symbol will be defined if the program ran successfully. This
will either on the C compiler commandline (by passing an option "-DSYMBOL"), in the "defines" method,
or via the "write_defines" method.
assert_compile_run
assert_compile_run(%args);
Calls "try_compile_run". If it fails, die with an "OS unsupported" message. Useful to call from Build.PL
or Makefile.PL.
Takes one extra optional argument:
diag => STRING
If present, this string will be appended to the failure message if one is generated. It may provide
more useful information to the user on why the OS is unsupported.
try_find_cflags_for
$success = try_find_cflags_for(%args);
Try to compile, link and execute the given source, using extra compiler flags.
When a usable combination is found, the flags are stored in the object for use in further compile
operations, or returned by "extra_compiler_flags". The method then returns true.
If no usable combination is found, it returns false.
Takes the following extra arguments:
source => STRING
Source code to compile
cflags => ARRAY of ARRAYs
Gives a list of sets of flags. Each set of flags should be strings in its own array reference.
define => STRING
Optional. If specified, then the named symbol will be defined if the program ran successfully. This
will either on the C compiler commandline (by passing an option "-DSYMBOL"), in the "defines" method,
or via the "write_defines" method.
try_find_include_dirs_for
$success = try_find_include_dirs_for(%args);
Try to compile, link and execute the given source, using extra include directories.
When a usable combination is found, the directories required are stored in the object for use in further
compile operations, or returned by "include_dirs". The method then returns true.
If no a usable combination is found, it returns false.
Takes the following arguments:
source => STRING
Source code to compile
dirs => ARRAY of ARRAYs
Gives a list of sets of dirs. Each set of dirs should be strings in its own array reference.
define => STRING
Optional. If specified, then the named symbol will be defined if the program ran successfully. This
will either on the C compiler commandline (by passing an option "-DSYMBOL"), in the "defines" method,
or via the "write_defines" method.
try_find_libraries_for
$success = try_find_libraries_for(%args);
Try to compile, link and execute the given source, when linked against a given set of extra libraries.
When a usable combination is found, the libraries required are stored in the object for use in further
link operations, or returned by "libraries". The method then returns true.
If no usable combination is found, it returns false.
Takes the following arguments:
source => STRING
Source code to compile
libs => ARRAY of STRINGs
Gives a list of sets of libraries. Each set of libraries should be space-separated.
define => STRING
Optional. If specified, then the named symbol will be defined if the program ran successfully. This
will either on the C compiler commandline (by passing an option "-DSYMBOL"), in the "defines" method,
or via the "write_defines" method.
try_find_library_dirs_for
$success = try_find_library_dirs_for(%args);
Try to compile, link and execute the given source, using extra library directories.
When a usable combination is found, the directories required are stored in the object for use in further
compile operations, or returned by "library_dirs". The method then returns true.
If no a usable combination is found, it returns false.
Takes the following arguments:
source => STRING
Source code to compile
dirs => ARRAY of ARRAYs
Gives a list of sets of dirs. Each set of dirs should be strings in its own array reference.
define => STRING
Optional. If specified, then the named symbol will be defined if the program ran successfully. This
will either on the C compiler commandline (by passing an option "-DSYMBOL"), in the "defines" method,
or via the "write_defines" method.
find_cflags_for
find_cflags_for(%args);
find_include_dirs_for
find_include_dirs_for(%args);
find_libraries_for
find_libraries_for(%args);
Calls "try_find_cflags_for", "try_find_include_dirs_for" or "try_find_libraries_for" respectively. If it
fails, die with an "OS unsupported" message.
Each method takes one extra optional argument:
diag => STRING
If present, this string will be appended to the failure message if one is generated. It may provide
more useful information to the user on why the OS is unsupported.
include_dirs
$dirs = include_dirs;
Returns the currently-configured include directories as an array.
library_dirs
$dirs = library_dirs;
Returns the currently-configured library directories as an array.
libraries
$libs = libraries;
Returns the currently-configured libraries as an array.
extra_compiler_flags
$flags = extra_compiler_flags;
Returns the currently-configured extra compiler flags as an array.
extra_linker_flags
$flags = extra_linker_flags;
Returns the currently-configured extra linker flags as an array.
push_include_dirs
push_include_dirs(@dirs);
Adds more include directories
push_library_dirs
push_library_dirs(@dirs);
Adds more library directories
push_libraries
push_libraries(@libs);
Adds more libraries
push_extra_compiler_flags
push_extra_compiler_flags(@flags);
Adds more compiler flags
push_extra_linker_flags
push_extra_linker_flags(@flags);
Adds more linker flags
define
define($symbol);
Adds a new defined symbol directly; either by appending to the compiler flags or writing it into the
defines file.
EXAMPLES
Socket Libraries
Some operating systems provide the BSD sockets API in their primary libc. Others keep it in a separate
library which should be linked against. The following example demonstrates how this would be handled.
find_libraries_for(
diag => 'no socket()',
libs => [ [], ['socket', 'nsl' ]],
source => q[
#include <sys/socket.h>
int main(int argc, char *argv) {
int fd = socket(PF_INET, SOCK_STREAM, 0);
if (fd < 0)
return 1;
return 0;
}
]);
Testing For Optional Features
Sometimes a function or ability may be optionally provided by the OS, or you may wish your module to be
useable when only partial support is provided, without requiring it all to be present. In these cases it
is traditional to detect the presence of this optional feature in the Build.PL script, and define a
symbol to declare this fact if it is found. The XS code can then use this symbol to select between
differing implementations. For example, the Build.PL:
try_compile_run(
define => 'HAVE_MANGO',
source => <<'EOF');
#include <mango.h>
#include <unistd.h>
int main(void) {
if (mango() != 0)
exit(1);
exit(0);
}
EOF
If the C code compiles and runs successfully, and exits with a true status, the symbol "HAVE_MANGO" will
be defined on the compiler commandline. This allows the XS code to detect it, for example
int
mango()
CODE:
#ifdef HAVE_MANGO
RETVAL = mango();
#else
croak("mango() not implemented");
#endif
OUTPUT:
RETVAL
This module will then still compile even if the operating system lacks this particular function. Trying
to invoke the function at runtime will simply throw an exception.
Linux Kernel Headers
Operating systems built on top of the Linux kernel often share a looser association with their kernel
version than most other operating systems. It may be the case that the running kernel is newer,
containing more features, than the distribution's libc headers would believe. In such circumstances it
can be difficult to make use of new socket options, ioctl()s, etc.. without having the constants that
define them and their parameter structures, because the relevant header files are not visible to the
compiler. In this case, there may be little choice but to pull in some of the kernel header files, which
will provide the required constants and structures.
The Linux kernel headers can be found using the /lib/modules directory. A fragment in Build.PL like the
following, may be appropriate.
chomp(my $uname_r = `uname -r);
my @dirs = (
[],
[ "/lib/modules/$uname_r/source/include" ],
);
find_include_dirs_for(
diag => "no PF_MOONLASER",
dirs => \@dirs,
source => <<'EOF');
#include <sys/socket.h>
#include <moon/laser.h>
int family = PF_MOONLASER;
struct laserwl lwl;
int main(int argc, char *argv[]) {
return 0;
}
EOF
This fragment will first try to compile the program as it stands, hoping that the libc headers will be
sufficient. If it fails, it will then try including the kernel headers, which should make the constant
and structure visible, allowing the program to compile.
AUTHOR
Leon Timmermans <fawaka@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by Leon Timmermans.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
programming language system itself.