types checking signal/callback functions revisited

[Trog <trog gtk org>]

I've been thinking about the problem of checking the types expected
by callback functions, and those actually declared by the function
itself. For example, the declaration of the function used in a call
to:

gint gdk_input_add( gint              source,
                    GdkInputCondition condition,
                    GdkInputFunction  function,
                    gpointer          data );

should be declared like:

void input_callback( gpointer          data,
                     gint              source, 
                     GdkInputCondition condition );

but there are no compile- or run-time checks that this is done
correctly.

Now, the only way I can think of actually getting the compiler to
check this is at function declaration. So, if we defined a macro
like:

#define GTK_INPUT_FUNC(f) void f( gpointer, gint, GdkInputCondition )

we could then forward declare our callback function with:

GTK_INPUT_FUNC(input_callback);

which would allow the compiler to perform a check that the
declaration and the definition match.

Similar things can be done with all the signal callbacks, and still 
allow us to keep the simplicity of using gtk_signal_connect.

Any thoughts or better ways of doing this?

Thanks

Tony


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