[qwertyuiop924]

I'm not sure it is. As junke pointed out below, however, some of this can be achieved through other, less intrusive methods, such as environments, which are actually used by the sc macro mechanism. You don't get it all, but it's usually enough to know that the error was triggered in the expansion of a macro on line <n>. That's dramatically better than most C error messages already. :-D