Evaluations of conditions SHOULD be handled through case statement. A
catch-all is only required, if the
Error messages should follow the indentation level of the wrapping function call statement. Code readability takes precedence, since we gain more code readability, than we loose error discoverability. It will "just" look a little weird, but I could swear I've seen other people doing it in their configure.ac and it wasn't too weird too me.