[cfe-dev] How can I use the result of a void expression? :p

[Chris Lattner]

On Aug 26, 2007, at 4:39 AM, Keith Bauer wrote:

> imac:Desktop keith$ cat > conditionalvoid.c
> extern void foo();
> extern void bar();
> void baz(int c) {
>   c ? foo() : bar();
> }
> imac:Desktop keith$ gcc -fsyntax-only -Wall -Wextra conditionalvoid.c
> imac:Desktop keith$ clang -fsyntax-only conditionalvoid.c
> conditionalvoid.c:4:3: warning: expression result unused
>   c ? foo() : bar();
>   ^~~~~~~~~~~~~~~~~
> 1 diagnostic generated.

Yep, that's a bug, but not because ?: has side effects.  It is  
because that warning should never be emitted for a void expression,  
patch here:
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of- 
Mon-20070820/001680.html

> ( ?: on void is perfectly legal according to C99 6.5.15 )

Sure.  Warnings are for code that is legal but questionable :)

Thanks,

-Chris