Anyone on ANSI standard C - (nf)

Guy Harris guy at rlgvax.UUCP
Fri Feb 10 15:17:46 AEST 1984

> I have a question about the effects of specifying parameter types in
> the ANSI C standard.  What will the exact effect be when the type of an
> actual parameter differs from the type given in the declaration?  Seems to
> me that while silently casting is usually the right thing, in some cases
> the compiler should issue warnings because the odds are good the
> user is making a mistake.  I think the compiler should cast silently
> if the declared and actual types are both arithmetic, regardless of
> length or signed/unsigned distinctions (leave warnings about lost
> accuracy to lint), or if the declared type is a pointer of any type and the
> actual parameter is the constant 0, but warn the user about everything
> else (e.g., using an int or char* where a FILE* was expected).

That's actually an implementation question to some degree; the Portable C
Compiler already issues warnings for the implicit conversions you mention.
I.e., if you have

	int foo;
	char *bar;
	FILE *bletch;

	foo = bar;
	bletch = bar;

you will get "Illegal combination of pointer and integer" for the first and
"Illegal pointer combination" for the second.  Any PCC-based implementation
of ANSI C would probably do exactly this, which is what you suggest.

	Guy Harris

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