NAME

glib-genmarshal - C code marshaller generation utility for GLib closures

SYNOPSIS

glib-genmarshal [OPTION...] [FILE...]

DESCRIPTION

glib-genmarshal is a small utility that generates C code marshallers for callback functions of the GClosure mechanism in the GObject sublibrary of GLib. The marshaller functions have a standard signature, they get passed in the invoking closure, an array of value structures holding the callback function parameters and a value structure for the return value of the callback. The marshaller is then responsible to call the respective C code function of the closure with all the parameters on the stack and to collect its return value.

glib-genmarshal takes a list of marshallers to generate as input. The marshaller list is either read from files passed as additional arguments on the command line; or from standard input, by using - as the input file.

Marshaller list format

The marshaller lists are processed line by line, a line can contain a comment in the form of

or a marshaller specification of the form

RTYPE:PTYPE
RTYPE:PTYPE,PTYPE
RTYPE:PTYPE,PTYPE,PTYPE

The RTYPE part specifies the callback's return type and the PTYPEs right to the colon specify the callback's parameter list, except for the first and the last arguments which are always pointers.

Parameter types

Currently, the following types are supported:

VOID

indicates no return type, or no extra parameters. If VOID is used as the parameter list, no additional parameters may be present.

BOOLEAN

for boolean types (gboolean)

CHAR

for signed char types (gchar)

UCHAR

for unsigned char types (guchar)

INT

for signed integer types (gint)

UINT

for unsigned integer types (guint)

LONG

for signed long integer types (glong)

ULONG

for unsigned long integer types (gulong)

INT64

for signed 64bit integer types (gint64)

UINT64

for unsigned 64bit integer types (guint64)

ENUM

for enumeration types (gint)

FLAGS

for flag enumeration types (guint)

FLOAT

for single-precision float types (gfloat)

DOUBLE

for double-precision float types (gdouble)

STRING

for string types (gchar*)

BOXED

for boxed (anonymous but reference counted) types (GBoxed*)

PARAM

for GParamSpec or derived types (GParamSpec*)

POINTER

for anonymous pointer types (gpointer)

OBJECT

for GObject or derived types (GObject*)

VARIANT

for GVariant types (GVariant*)

NONE

deprecated alias for VOID

BOOL

deprecated alias for BOOLEAN

OPTIONS

--header

Generate header file contents of the marshallers. This option is mutually exclusive with the --body option.

--body

Generate C code file contents of the marshallers. This option is mutually exclusive with the --header option.

--prefix=PREFIX

Specify marshaller prefix. The default prefix is `g_cclosure_user_marshal'.

--skip-source

Skip source location remarks in generated comments.

--stdinc

Use the standard marshallers of the GObject library, and include glib-object.h in generated header files. This option is mutually exclusive with the --nostdinc option.

--nostdinc

Do not use the standard marshallers of the GObject library, and skip glib-object.h include directive in generated header files. This option is mutually exclusive with the --stdinc option.

--internal

Mark generated functions as internal, using G_GNUC_INTERNAL.

--valist-marshallers

Generate valist marshallers, for use with g_signal_set_va_marshaller().

-v, --version

Print version information.

--g-fatal-warnings

Make warnings fatal, that is, exit immediately once a warning occurs.

-h, --help

Print brief help and exit.

-v, --version

Print version and exit.

--output=FILE

Write output to FILE instead of the standard output.

--prototypes

Generate function prototypes before the function definition in the C source file, in order to avoid a missing-prototypes compiler warning. This option is only useful when using the --body option.

--pragma-once

Use the once pragma instead of an old style header guard when generating the C header file. This option is only useful when using the --header option.

--include-header=HEADER

Adds a #include directive for the given file in the C source file. This option is only useful when using the --body option.

-D SYMBOL[=VALUE]

Adds a #define C pre-processor directive for SYMBOL and its given VALUE, or "1" if the value is unset. You can use this option multiple times; if you do, all the symbols will be defined in the same order given on the command line, before the symbols undefined using the -U option. This option is only useful when using the --body option.

-U SYMBOL

Adds a #undef C pre-processor directive to undefine the given SYMBOL. You can use this option multiple times; if you do, all the symbols will be undefined in the same order given on the command line, after the symbols defined using the -D option. This option is only useful when using the --body option.

--quiet

Minimizes the output of glib-genmarshal, by printing only warnings and errors. This option is mutually exclusive with the --verbose option.

--verbose

Increases the verbosity of glib-genmarshal, by printing debugging information. This option is mutually exclusive with the --quiet option.

USING GLIB-GENMARSHAL WITH MESON

Meson supports generating closure marshallers using glib-genmarshal out of the box in its "gnome" module.

In your meson.build file you will typically call the gnome.genmarshal() method with the source list of marshallers to generate:

gnome = import('gnome')
marshal_files = gnome.genmarshal('marshal',
  sources: 'marshal.list',
  internal: true,
)

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

•a build target for the source file

•a build target for the header file

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:

mainlib = library('project',
  sources: project_sources + marshal_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:

mainlib_dep = declare_dependency(sources: marshal_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[1].

For more information on how to use the method, see the Meson documentation for gnome.genmarshal()[2].

USING GLIB-GENMARSHAL WITH AUTOTOOLS

In order to use glib-genmarshal 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.

PKG_PROG_PKG_CONFIG([0.28])
PKG_CHECK_VAR([GLIB_GENMARSHAL], [glib-2.0], [glib_genmarshal])

In your Makefile.am file you will typically need very simple rules to generate the C files needed for the build.

marshal.h: marshal.list
        $(AM_V_GEN)$(GLIB_GENMARSHAL) \
                --header \
                --output=$@ \
                $<
marshal.c: marshal.list marshal.h
        $(AM_V_GEN)$(GLIB_GENMARSHAL) \
                --include-header=marshal.h \
                --body \
                --output=$@ \
                $<
BUILT_SOURCES += marshal.h marshal.c
CLEANFILES += marshal.h marshal.c
EXTRA_DIST += marshal.list

In the example above, the first rule generates the header file and depends on a marshal.list file in order to regenerate the result in case the marshallers list is updated. The second rule generates the source file for the same marshal.list, and includes the file generated by the header rule.

EXAMPLE

To generate marshallers for the following callback functions:

void   foo (gpointer data1,
            gpointer data2);
void   bar (gpointer data1,
            gint     param1,
            gpointer data2);
gfloat baz (gpointer data1,
            gboolean param1,
            guchar   param2,
            gpointer data2);

The marshaller.list file has to look like this:

VOID:VOID
VOID:INT
FLOAT:BOOLEAN,UCHAR

and you call glib-genmarshal like this:

glib-genmarshal --header marshaller.list > marshaller.h
glib-genmarshal --body marshaller.list > marshaller.c

The generated marshallers have the arguments encoded in their function name. For this particular list, they are

g_cclosure_user_marshal_VOID__VOID(...),
g_cclosure_user_marshal_VOID__INT(...),
g_cclosure_user_marshal_FLOAT__BOOLEAN_UCHAR(...).

They can be used directly for GClosures or be passed in as the GSignalCMarshaller c_marshaller; argument upon creation of signals:

GClosure *cc_foo, *cc_bar, *cc_baz;
cc_foo = g_cclosure_new (NULL, foo, NULL);
g_closure_set_marshal (cc_foo, g_cclosure_user_marshal_VOID__VOID);
cc_bar = g_cclosure_new (NULL, bar, NULL);
g_closure_set_marshal (cc_bar, g_cclosure_user_marshal_VOID__INT);
cc_baz = g_cclosure_new (NULL, baz, NULL);
g_closure_set_marshal (cc_baz, g_cclosure_user_marshal_FLOAT__BOOLEAN_UCHAR);

NOTES

1.: corresponding Meson FAQ entry

https://mesonbuild.com/FAQ.html#how-do-i-tell-meson-that-my-sources-use-generated-headers

2.: Meson documentation for gnome.genmarshal()

https://mesonbuild.com/Gnome-module.html#gnomegenmarshal