Re: [Vala] Define constant at compile time

[Jan Hudec <bulb ucw cz>]

On Tue, Nov 16, 2010 at 18:36:07 +0100, Andrea Corbellini wrote:
> I want to specify the constant UI_FILE at compile time, but I don't know
> how to do that. In C I would write something like that:
>
>   #ifndef UI_FILE
>   #define UI_FILE "default-path.xml"
>   #endif
>
> and then I would call gcc with the option -DUI_FILE="something". I've
> tried to use the -D option of the Vala compiler, but it doesn't seem to
> work as I expect. Any ideas?

There are two ways:

 1. Define it as 
        static const string UI_FILE = "@ui_file@"
    in a .vala file and have it substituted by autoconf (similar mechanizm
    exists in any other build tool as well).

 2. Define it as
        [CCode(cname="UI_FILE" cheader_filename="defaults.h")]
        extern const string UI_FILE;
    in a .vala file (or in a .vapi file in which case it's extern
    implicitly), put the defines you cited above in this "defaults.h" file
    and optionally pass the -D option to the C compiler. You can pass options
    through vala to the C compiler by prefixing them with -X like:
        vala ... -X -DUI_FILE=\"something\" ...

-- 
                                                 Jan 'Bulb' Hudec <bulb ucw cz>