rules for __builtin_types_compatible_p??

Matthew Woehlke
Tue Nov 11 18:22:00 GMT 2008

Kevin P. Fleming wrote:
> Matthew Woehlke wrote:
>> ...but this ("typeof(&((b)[0]))") seems like it might work, assuming
>> that "b" is a string literal, a [const] char*, or a [const] char[].
> Yes, in fact, this does seem to work:
> #define S_OR(a, b) ({typeof(&((a)[0])) __x = (a); ast_strlen_zero(__x) ?
> (b) : __x;})

Ah, simplification ;-).

> This macro appears to work fine, compiles in all our existing usage
> situations (combinations of char *, char [], const vs. non-const) and
> provides the side-effect-safe evaluation of its arguments I was looking
> for in the first place. Thanks!

You're welcome! (Now, if only I knew why that odd incantation is 
needed... :-) )

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