@findex #error
The directive @samp{#error} causes the preprocessor to report a fatal
error. The rest of the line that follows @samp{#error} is used as the
-error message.
+error message. The line must consist of complete tokens.
You would use @samp{#error} inside of a conditional that detects a
combination of parameters which you know the program does not properly
@smallexample
@group
#ifdef __vax__
-#error Won't work on Vaxen. See comments at get_last_object.
+#error "Won't work on Vaxen. See comments at get_last_object."
#endif
@end group
@end smallexample