NAME¶
Glib::version - Library Versioning Utilities
SYNOPSIS¶
# require at least version 1.021 of the Glib module
use Glib '1.021';
# g_set_application_name() was introduced in GLib 2.2.0, and
# first supported by version 1.040 of the Glib Perl module.
if ($Glib::VERSION >= 1.040 and Glib->CHECK_VERSION (2,2,0)) {
Glib::set_application_name ('My Cool Program');
}
DESCRIPTION¶
Both the Glib module and the GLib C library are works-in-progress, and their
interfaces grow over time. As more features are added to each, and your code
uses those new features, you will introduce version-specific dependencies, and
naturally, you'll want to be able to code around them. Enter the versioning
API.
For simple Perl modules, a single version number is sufficient; however, Glib is
a binding to another software library, and this introduces some complexity. We
have three versions that fully specify the API available to you.
- Perl Bindings Version
- Perl modules use a version number, and Glib is no
exception. $Glib::VERSION is the version of the
current Glib module. By ad hoc convention, gtk2-perl modules generally use
version numbers in the form x.yyz, where even yy values denote stable
releases and z is a patchlevel.
$Glib::VERSION
use Glib 1.040; # require at least version 1.040
- Compile-time ("Bound") Library Version
- This is the version of the GLib C library that was
available when the Perl module was compiled and installed. These version
constants are equivalent to the version macros provided in the GLib C
headers. GLib uses a major.minor.micro convention, where even minor
versions are stable. (gtk2-perl does not officially support unstable
versions.)
Glib::MAJOR_VERSION
Glib::MINOR_VERSION
Glib::MICRO_VERSION
Glib->CHECK_VERSION($maj,$min,$mic)
- Run-time ("Linked") Library Version
- This is the version of the GLib C library that is available
at run time; it may be newer than the compile-time version, but should
never be older. These are equivalent to the version variables exported by
the GLib C library.
Glib::major_version
Glib::minor_version
Glib::micro_version
Which one do I use when?¶
Where do you use which version? It depends entirely on what you're doing. Let's
explain by example:
- o Use the Perl module version for bindings support
issues
- You need to register a new enum for use as the type of an
object property. This is something you can do with all versions of the
underlying C library, but which wasn't supported in the Glib Perl module
until $Glib::VERSION >= 1.040.
- o Use the bound version for library features
- You want to call Glib::set_application_name to set a
human-readable name for your application (which is used by various parts
of Gtk2 and Gnome2). g_set_application_name() (the underlying C
function) was added in version 2.2.0 of glib, and support for it was
introduced into the Glib Perl module in Glib version 1.040. However, you
can build the Perl module against any stable 2.x.x version of glib, so you
might not have that function available even if your Glib module is new
enough!
Thus, you need to check two things to see if the this function is
available:
if ($Glib::VERSION >= 1.040 && Glib->CHECK_VERSION (2,2,0)) {
# it's available, and we can call it!
Glib::set_application_name ('My Cool Application');
}
Now what happens if you installed the Perl module when your system had glib
2.0.6, and you upgraded glib to 2.4.1? Wouldn't
g_set_application_name() be available? Well, it's there, under the
hood, but the bindings were compiled when it wasn't there, so you won't be
able to call it! That's why we check the "bound" or compile-time
version. By the way, to enable support for the new function, you'd need to
reinstall (or upgrade) the Perl module.
- o Use the linked version for runtime work-arounds
- Suppose there's a function whose API did not change, but
whose implementation had a bug in one version that was fixed in another
version. To determine whether you need to apply a workaround, you would
check the version that is actually being used at runtime.
if (Glib::major_version == 2 &&
Glib::minor_version == 2 &&
Glib::micro_version == 1) {
# work around bug that exists only in glib 2.2.1.
}
In practice, such situations are very rare.
METHODS¶
boolean = Glib->CHECK_VERSION ($required_major,
$required_minor, $required_micro)¶
- •
- $required_major (integer)
- •
- $required_minor (integer)
- •
- $required_micro (integer)
Provides a mechanism for checking the version information that Glib was compiled
against. Essentially equvilent to the macro GLIB_CHECK_VERSION.
(MAJOR, MINOR, MICRO) = Glib->GET_VERSION_INFO¶
Shorthand to fetch as a list the glib version for which Glib was compiled. See
"Glib::MAJOR_VERSION", etc.
integer = Glib::MAJOR_VERSION¶
Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MAJOR_VERSION.
integer = Glib::MICRO_VERSION¶
Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MICRO_VERSION.
integer = Glib::MINOR_VERSION¶
Provides access to the version information that Glib was compiled against.
Essentially equivalent to the #define's GLIB_MINOR_VERSION.
integer = Glib::major_version¶
Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_major_version.
integer = Glib::micro_version¶
Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_micro_version.
integer = Glib::minor_version¶
Provides access to the version information that Glib is linked against.
Essentially equivalent to the global variable glib_minor_version.
SEE ALSO¶
Glib
COPYRIGHT¶
Copyright (C) 2003-2011 by the gtk2-perl team.
This software is licensed under the LGPL. See Glib for a full notice.