I had a problem recently in a gtkd program i wrote. The program could only find a certain shared library (libatk) if the environment variable GTK_BASEPATH was set; otherwise, it would throw an exception before main() started.

I did not want to set that environment variable, or any environment variable, either on the command line or in a shell initialization script. Instead i wanted to set it from within the executable.

I did not have a solution for this, but Rikki Cattermole told me about pragma crtconstructor. So now i have a short function which runs after the c-runtime is setup but before the d-runtime is, and it sets GTKBASEPATH. Right now, it looks like this:

pragma( crt_constructor ) extern( C ) void _env_setup( ) {
  import core.sys.posix.stdlib : getenv, putenv;
  auto val = getenv( cast( const char * ) "GTK_BASEPATH".ptr );
  if ( val ) {
    writeln( "GTK_BASEPATH already has a value, not setting" );
  } else {
    writeln( "Setting GTK_BASEPATH to /opt/local/lib" );

This works, at least for dmd (and given a std.stdio import for the writeln), but actually it's not really doing all i want.

I would like to write an arbitrary amount of d code, including routines that require GC, that runs before gtkd does. (For the crt_constructor code, one is limited in what can be written. Nothing that requires GC can be written, because the d runtime has not yet been set up.)

In some cases, for example if the program gets a --version or a --help argument, i would not want to run gtkd at all, but just exit(0) out; in these cases, lack of a shared library does not matter.

And if a shared library is missing, maybe the software might query the user directly on where to find it (using stdout/stdin question/response).

So, are there any pre-initialization hooks in gtkd that i can assign that will be guaranteed to be called before any serious initialization is run (especially before any shared libraries are loaded)?

Or are there other alternatives to the crt_constructor pragma?

This is not urgent, since Rikki's code works for me, but on the d language forum it was suggested that i check with the gtkd forum also.