In C you can return a struct, however a better approach is to use a context object which also contains error information, like:

    ctx_t* ctx = ctx_new();
    if (!ctx) ... fail ...
    if (!ctx_parse(ctx, code)) {
        show_error_message(ctx_erline(ctx), ctx_ercol(ctx));
        ... more fail ...
        ctx_free(ctx); /* often done in a goto'd section to avoid missing frees*/
    }

This also allows you to extend the APIs functionality, error information, etc in the future while remaining backwards compatible.