Re: [Emacs-diffs] master b7fa6b1 1/4: Simplify use of FOR_EACH_TAIL

[Paul Eggert]

On 02/06/2017 09:38 AM, Davis Herring wrote:
> Did you just mean that you couldn't have that variable declared and 
> also the tortoise integer declared because they were different types 
> (and you didn't want to open a pair of braces in the macro that would 
> have to be closed later)? 

Yes, that sort of thing, although it's not that they are different types.

Portable C99 code cannot declare two or more identifiers in the same 
for-loop, due to an ambiguity in the C99 standard, which says (6.8.5 
para 3) "The declaration part of a for statement shall only declare 
identifiers for objects having storage class auto or register." This 
constraint can be interpreted as meaning (A) when a for-statement 
declares an object's name, the name must have storage class auto or 
register, or (B) all identifiers declared by a for-statement must name 
objects with storage class auto or register. Although I suspect (A) was 
intended and that's what GCC does, (B) is also a plausible 
interpretation and that's what Clang does. Interpretation (B) disallows 
anonymous structs here, as such structs declare member names.