glib/docs/reference/gobject/glib-genmarshal.xml

<refentry id="glib-genmarshal" lang="en">

<refentryinfo>
  <title>glib-genmarshal</title>
  <productname>GObject</productname>
  <authorgroup>
    <author>
      <contrib>Developer</contrib>
      <firstname>Emmanuele</firstname>
      <surname>Bassi</surname>
    </author>
    <author>
      <contrib>Original developer</contrib>
      <firstname>Tim</firstname>
      <surname>Janik</surname>
    </author>
  </authorgroup>
</refentryinfo>

<refmeta>
<refentrytitle>glib-genmarshal</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="manual">User Commands</refmiscinfo>
</refmeta>

<refnamediv>
<refname>glib-genmarshal</refname>
<refpurpose>C code marshaller generation utility for GLib closures</refpurpose>
</refnamediv>

<refsynopsisdiv>
<cmdsynopsis>
<command>glib-genmarshal</command>
<arg choice="opt" rep="repeat">OPTION</arg>
<arg choice="opt" rep="repeat">FILE</arg>
</cmdsynopsis>
</refsynopsisdiv>

<refsect1><title>Description</title>
<para><command>glib-genmarshal</command> 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.
</para>

<para><command>glib-genmarshal</command> 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 <literal>-</literal> as the
input file.
</para>

<refsect2><title>Marshaller list format</title>
<para>
The marshaller lists are processed line by line, a line can contain a
comment in the form of
<informalexample><programlisting>
# this is a comment
</programlisting></informalexample>
or a marshaller specification of the form
<programlisting>
<replaceable>RTYPE</replaceable>:<replaceable>PTYPE</replaceable>
<replaceable>RTYPE</replaceable>:<replaceable>PTYPE</replaceable>,<replaceable>PTYPE</replaceable>
<replaceable>RTYPE</replaceable>:<replaceable>PTYPE</replaceable>,<replaceable>PTYPE</replaceable>,<replaceable>PTYPE</replaceable>
</programlisting>
</para>
<para>
The <replaceable>RTYPE</replaceable> part specifies the callback's return
type and the <replaceable>PTYPE</replaceable>s right to the colon specify
the callback's parameter list, except for the first and the last arguments
which are always pointers.
</para>
</refsect2>
<refsect2><title>Parameter types</title>
<para>
Currently, the following types are supported:
<variablelist>
<varlistentry>
<term><replaceable>VOID</replaceable></term>
<listitem><para>
indicates no return type, or no extra parameters.
If <replaceable>VOID</replaceable> is used as the parameter list, no
additional parameters may be present.
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>BOOLEAN</replaceable></term>
<listitem><para>
for boolean types (gboolean)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>CHAR</replaceable></term>
<listitem><para>
for signed char types (gchar)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>UCHAR</replaceable></term>
<listitem><para>
for unsigned char types (guchar)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>INT</replaceable></term>
<listitem><para>
for signed integer types (gint)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>UINT</replaceable></term>
<listitem><para>
for unsigned integer types (guint)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>LONG</replaceable></term>
<listitem><para>
for signed long integer types (glong)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>ULONG</replaceable></term>
<listitem><para>
for unsigned long integer types (gulong)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>INT64</replaceable></term>
<listitem><para>
for signed 64bit integer types (gint64)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>UINT64</replaceable></term>
<listitem><para>
for unsigned 64bit integer types (guint64)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>ENUM</replaceable></term>
<listitem><para>
for enumeration types (gint)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>FLAGS</replaceable></term>
<listitem><para>
for flag enumeration types (guint)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>FLOAT</replaceable></term>
<listitem><para>
for single-precision float types (gfloat)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>DOUBLE</replaceable></term>
<listitem><para>
for double-precision float types (gdouble)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>STRING</replaceable></term>
<listitem><para>
for string types (gchar*)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>BOXED</replaceable></term>
<listitem><para>
for boxed (anonymous but reference counted) types (GBoxed*)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>PARAM</replaceable></term>
<listitem><para>
for GParamSpec or derived types (GParamSpec*)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>POINTER</replaceable></term>
<listitem><para>
for anonymous pointer types (gpointer)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>OBJECT</replaceable></term>
<listitem><para>
for GObject or derived types (GObject*)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>VARIANT</replaceable></term>
<listitem><para>
for GVariant types (GVariant*)
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>NONE</replaceable></term>
<listitem><para>
deprecated alias for <replaceable>VOID</replaceable>
</para></listitem>
</varlistentry>

<varlistentry>
<term><replaceable>BOOL</replaceable></term>
<listitem><para>
deprecated alias for <replaceable>BOOLEAN</replaceable>
</para></listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>

<refsect1><title>Options</title>
<variablelist>

<varlistentry>
<term><option>--header</option></term>
<listitem><para>
Generate header file contents of the marshallers. This option is mutually
exclusive with the <option>--body</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--body</option></term>
<listitem><para>
Generate C code file contents of the marshallers. This option is mutually
exclusive with the <option>--header</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--prefix=<replaceable>PREFIX</replaceable></option></term>
<listitem><para>
Specify marshaller prefix. The default prefix is <literal>`g_cclosure_user_marshal'</literal>.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--skip-source</option></term>
<listitem><para>
Skip source location remarks in generated comments.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--stdinc</option></term>
<listitem><para>
Use the standard marshallers of the GObject library, and include
<filename>glib-object.h</filename> in generated header files. This
option is mutually exclusive with the <option>--nostdinc</option>
option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--nostdinc</option></term>
<listitem><para>
Do not use the standard marshallers of the GObject library, and skip
<filename>glib-object.h</filename> include directive in generated header files.
This option is mutually exclusive with the <option>--stdinc</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--internal</option></term>
<listitem><para>
Mark generated functions as internal, using <literal>G_GNUC_INTERNAL</literal>.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--valist-marshallers</option></term>
<listitem><para>
Generate valist marshallers, for use with <function>g_signal_set_va_marshaller()</function>.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>-v</option>, <option>--version</option></term>
<listitem><para>
Print version information.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--g-fatal-warnings</option></term>
<listitem><para>
Make warnings fatal, that is, exit immediately once a warning occurs.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>-h</option>, <option>--help</option></term>
<listitem><para>
Print brief help and exit.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>-v</option>, <option>--version</option></term>
<listitem><para>
Print version and exit.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--output=FILE</option></term>
<listitem><para>
Write output to <replaceable>FILE</replaceable> instead of the standard output.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--prototypes</option></term>
<listitem><para>
Generate function prototypes before the function definition in the C source
file, in order to avoid a <literal>missing-prototypes</literal> compiler
warning. This option is only useful when using the <option>--body</option>
option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--pragma-once</option></term>
<listitem><para>
Use the <literal>once</literal> pragma instead of an old style header guard
when generating the C header file. This option is only useful when using the
<option>--header</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--include-header=<replaceable>HEADER</replaceable></option></term>
<listitem><para>
Adds a <literal>#include</literal> directive for the given file in the C
source file. This option is only useful when using the <option>--body</option>
option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>-D <replaceable>SYMBOL[=VALUE]</replaceable></option></term>
<listitem><para>
Adds a <literal>#define</literal> C pre-processor directive for
<replaceable>SYMBOL</replaceable> and its given <replaceable>VALUE</replaceable>,
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 <option>-U</option> option. This option is only
useful when using the <option>--body</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>-U <replaceable>SYMBOL</replaceable></option></term>
<listitem><para>
Adds a <literal>#undef</literal> C pre-processor directive to undefine the
given <replaceable>SYMBOL</replaceable>. 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 <option>-D</option> option.
This option is only useful when using the <option>--body</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--quiet</option></term>
<listitem><para>
Minimizes the output of <command>glib-genmarshal</command>, by printing only
warnings and errors. This option is mutually exclusive with the
<option>--verbose</option> option.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--verbose</option></term>
<listitem><para>
Increases the verbosity of <command>glib-genmarshal</command>, by printing
debugging information. This option is mutually exclusive with the
<option>--quiet</option> option.
</para></listitem>
</varlistentry>

</variablelist>
</refsect1>

<refsect1><title>Using <command>glib-genmarshal</command> with Meson</title>
<para>
Meson supports generating closure marshallers using <command>glib-genmarshal</command>
out of the box in its "gnome" module.
</para>

<para>
In your <filename>meson.build</filename> file you will typically call the
<literal>gnome.genmarshal()</literal> method with the source list of marshallers
to generate:
</para>
<informalexample><programlisting>
gnome = import('gnome')
marshal_files = gnome.genmarshal('marshal',
  sources: 'marshal.list',
  internal: true,
)
</programlisting></informalexample>
<para>
The <literal>marshal_files</literal> variable will contain an array of two elements
in the following order:
</para>
<itemizedlist>
  <listitem><para>a build target for the source file</para></listitem>
  <listitem><para>a build target for the header file</para></listitem>
</itemizedlist>
<para>
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:
</para>
<informalexample><programlisting>
mainlib = library('project',
  sources: project_sources + marshal_files,
  ...
)
</programlisting></informalexample>
</refsect1>

<refsect1><title>Using <command>glib-genmarshal</command> with Autotools</title>
<para>
In order to use <command>glib-genmarshal</command> in your project when using
Autotools as the build system, you will first need to modify your
<filename>configure.ac</filename> file to ensure you find the appropriate
command using <command>pkg-config</command>, similarly as to how you discover
the compiler and linker flags for GLib.
</para>
<informalexample><programlisting>
PKG_PROG_PKG_CONFIG([0.28])

PKG_CHECK_VAR([GLIB_GENMARSHAL], [glib-2.0], [glib_genmarshal])
</programlisting></informalexample>
<para>
In your <filename>Makefile.am</filename> file you will typically need very
simple rules to generate the C files needed for the build.
</para>
<informalexample><programlisting>
marshal.h: marshal.list
        $(AM_V_GEN)$(GLIB_GENMARSHAL) \
                --header \
                --output=$@ \
                $&lt;

marshal.c: marshal.list marshal.h
        $(AM_V_GEN)$(GLIB_GENMARSHAL) \
                --include-header=marshal.h \
                --body \
                --output=$@ \
                $&lt;

BUILT_SOURCES += marshal.h marshal.c
CLEANFILES += marshal.h marshal.c
EXTRA_DIST += marshal.list
</programlisting></informalexample>
<para>
In the example above, the first rule generates the header file and depends on
a <filename>marshal.list</filename> file in order to regenerate the result in
case the marshallers list is updated. The second rule generates the source file
for the same <filename>marshal.list</filename>, and includes the file generated
by the header rule.
</para>
</refsect1>

<refsect1><title>Example</title>
<para>
To generate marshallers for the following callback functions:
</para>
<informalexample><programlisting>
void   foo (gpointer data1,
            gpointer data2);
void   bar (gpointer data1,
            gint     param1,
            gpointer data2);
gfloat baz (gpointer data1,
            gboolean param1,
            guchar   param2,
            gpointer data2);
</programlisting></informalexample>
<para>
The <filename>marshaller.list</filename> file has to look like this:
</para>
<programlisting>
VOID:VOID
VOID:INT
FLOAT:BOOLEAN,UCHAR
</programlisting>
<para>
and you call glib-genmarshal like this:
</para>
<programlisting>
glib-genmarshal --header marshaller.list > marshaller.h
glib-genmarshal --body marshaller.list > marshaller.c
</programlisting>
<para>
The generated marshallers have the arguments encoded in their function name.
For this particular list, they are
</para>
<programlisting>
g_cclosure_user_marshal_VOID__VOID(...),
g_cclosure_user_marshal_VOID__INT(...),
g_cclosure_user_marshal_FLOAT__BOOLEAN_UCHAR(...).
</programlisting>
<para>
They can be used directly for GClosures or be passed in as the
GSignalCMarshaller c_marshaller; argument upon creation of signals:
</para>
<informalexample><programlisting>
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);
</programlisting></informalexample>
</refsect1>
<refsect1><title>See also</title>
<para>
<citerefentry>
<refentrytitle>glib-mkenums</refentrytitle>
<manvolnum>1</manvolnum>
</citerefentry>
</para>
</refsect1>
</refentry>