Description

glib-mkenums is a small utility that parses C code to extract enum definitions and produces enum descriptions based on text templates specified by the user. Typically, you can use this tool to generate enumeration types for the GType type system, for GObject properties and signal marshalling; additionally, you can use it to generate enumeration values of GSettings schemas.

glib-mkenums takes a list of valid C code files as input. The options specified control the text that generated, substituting various keywords enclosed in @ characters in the templates.

Since version 2.74, GLib provides the G_DEFINE_ENUM_TYPE and G_DEFINE_FLAGS_TYPE C pre-processor macros. These macros can be used to define a GType for projects that have few, small enumeration types without going through the complexities of generating code at build time.

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typedef enum
{
  PREFIX_THE_XVALUE    = 1 << 3,
  PREFIX_ANOTHER_VALUE = 1 << 4
} PrefixTheXEnum;

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typedef enum /*< skip >*/
{
  PREFIX_FOO
} PrefixThisEnumWillBeSkipped;
typedef enum /*< flags,prefix=PREFIX,since=1.0 >*/
{
  PREFIX_THE_ZEROTH_VALUE,	/*< skip >*/
  PREFIX_THE_FIRST_VALUE,
  PREFIX_THE_SECOND_VALUE,
  PREFIX_THE_THIRD_VALUE,	/*< nick=the-last-value >*/
} PrefixTheFlagsEnum;

Options

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/*** BEGIN section ***/
/*** END section ***/

Using templates

Instead of passing the various sections of the generated file to the command line of glib-mkenums, it's strongly recommended to use a template file, especially for generating C sources.

A C header template file will typically look like this:

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/*** BEGIN file-header ***/
#pragma once

/* Include the main project header */
#include "project.h"

G_BEGIN_DECLS
/*** END file-header ***/

/*** BEGIN file-production ***/

/* enumerations from "@basename@" */
/*** END file-production ***/

/*** BEGIN value-header ***/
GType @enum_name@_get_type (void) G_GNUC_CONST;
#define @ENUMPREFIX@_TYPE_@ENUMSHORT@ (@enum_name@_get_type ())
/*** END value-header ***/

/*** BEGIN file-tail ***/
G_END_DECLS
/*** END file-tail ***/

A C source template file will typically look like this:

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/*** BEGIN file-header ***/
#include "config.h"
#include "enum-types.h"

/*** END file-header ***/

/*** BEGIN file-production ***/
/* enumerations from "@basename@" */
/*** END file-production ***/

/*** BEGIN value-header ***/
GType
@enum_name@_get_type (void)
{
  static gsize static_g_@type@_type_id;

  if (g_once_init_enter (&static_g_@type@_type_id))
    {
      static const G@Type@Value values[] = {
/*** END value-header ***/

/*** BEGIN value-production ***/
            { @VALUENAME@, "@VALUENAME@", "@valuenick@" },
/*** END value-production ***/

/*** BEGIN value-tail ***/
            { 0, NULL, NULL }
      };

      GType g_@type@_type_id =
        g_@type@_register_static (g_intern_static_string ("@EnumName@"), values);

      g_once_init_leave (&static_g_@type@_type_id, g_@type@_type_id);
    }
  return static_g_@type@_type_id;
}

/*** END value-tail ***/

Template files are easier to modify and update, and can be used to generate various types of outputs using the same command line or tools during the build.

Using glib-mkenums with Meson

Meson supports generating enumeration types using glib-mkenums out of the box in its "gnome" module.

In your meson.build file you will typically call the gnome.mkenums_simple() method to generate idiomatic enumeration types from a list of headers to inspect:

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project_headers = [
  'project-foo.h',
  'project-bar.h',
  'project-baz.h',
]

gnome = import('gnome')
enum_files = gnome.mkenums_simple('enum-types',
  sources: project_headers,
)

The enum_files variable will contain an array of two elements in the following order:

You should use the returned objects to provide a dependency on every other build target that references the source or header file; for instance, if you are using the source to build a library:

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mainlib = library('project',
  sources: project_sources + enum_files,
  ...
)

Additionally, if you are including the generated header file inside a build target that depends on the library you just built, you must ensure that the internal dependency includes the generated header as a required source file:

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mainlib_dep = declare_dependency(sources: enum_files[1], link_with: mainlib)

You should not include the generated source file as well, otherwise it will be built separately for every target that depends on it, causing build failures. To know more about why all this is required, please refer to the corresponding Meson FAQ entry.

If you are generating C header and source files that require special templates, you can use gnome.mkenums() to provide those headers, for instance:

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enum_files = gnome.mkenums('enum-types',
  sources: project_headers,
  h_template: 'enum-types.h.in',
  c_template: 'enum-types.c.in',
  install_header: true,
)

For more information, see the Meson documentation for gnome.mkenums().

Using glib-mkenums with Autotools

In order to use glib-mkenums in your project when using Autotools as the build system, you will first need to modify your configure.ac file to ensure you find the appropriate command using pkg-config, similarly as to how you discover the compiler and linker flags for GLib.

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PKG_PROG_PKG_CONFIG([0.28])

PKG_CHECK_VAR([GLIB_MKENUMS], [glib-2.0], [glib_mkenums])

In your Makefile.am file you will typically use rules like these:

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# A list of headers to inspect
project_headers = \
        project-foo.h \
        project-bar.h \
        project-baz.h

enum-types.h: $(project_headers) enum-types.h.in
        $(AM_V_GEN)$(GLIB_MKENUMS) \
                --template=enum-types.h.in \
                --output=$@ \
                $(project_headers)

enum-types.c: $(project_headers) enum-types.c.in enum-types.h
        $(AM_V_GEN)$(GLIB_MKENUMS) \
                --template=enum-types.c.in \
                --output=$@ \
                $(project_headers)

# Build the enum types files before every other target
BUILT_SOURCES += enum-types.h enum-types.c
CLEANFILES += enum-types.h enum-types.c
EXTRA_DIST += enum-types.h.in enum-types.c.in

In the example above, we have a variable called project_headers where we reference all header files we want to inspect for generating enumeration GTypes. In the enum-types.h rule we use glib-mkenums with a template called enum-types.h.in in order to generate the header file; similarly, in the enum-types.c rule we use a template called enum-types.c.in.

See also

glib-genmarshal(1)