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>
<para>
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:
</para>
<informalexample><programlisting>
mainlib_dep = declare_dependency(sources: marshal_files[1], link_with: mainlib)
</programlisting></informalexample>
<para>
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
<ulink url="https://mesonbuild.com/FAQ.html#how-do-i-tell-meson-that-my-sources-use-generated-headers">
corresponding Meson FAQ entry</ulink>.
</para>
<para>
For more information on how to use the method, see the
<ulink url="https://mesonbuild.com/Gnome-module.html#gnomegenmarshal">Meson
documentation for <literal>gnome.genmarshal()</literal></ulink>.
</para>
</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>