#elsif

[Joern Rennecke]

>    Date: Tue, 7 Apr 1998 12:08:20 +0200 (MET DST)
>    From: "Philippe De Muyter" <phdm@macqel.be>
> 
>    #if defined(A)
> 	   printf("A defined\n");
>    #elsif  defined(B)
> 	   printf("B undefined\n");
>    #else   /* nor A nor B */
> 	   printf("nor A nor B defined\n");
>    #endif
> 
> As I read the C standard, if A is not defined, then GCC is required to
> accept that program fragment, though I admit the standard's wording is
> not entirely clear.
> 
> It might be useful for cpp to warn about skipped, unknown directives
> if -W or -Wall is specified.

IIRC the standard allows any number of warnings, no matter how bogus they
are.  So why not always warn about #elsif - it seems an obvious enough
typo to warn about even if we don't want to warn about unknown directives
in general.