On 02/06/2017 07:37 AM, Eli Zaretskii wrote:
> Why is it so important to make sure it doesn't survive the loop?  If
> for optimizations, then I'd expect modern compilers to be smart enough
> to produce the same code whether it does or doesn't survive.

It's not so much compilers as human readers of the code. Admittedly it 
is a minor issue.

> We have similar macros elsewhere, e.g. FOR_EACH_FRAME,
> FOR_EACH_BUFFER, etc.  It's IMO a pity to have this one different.

Good point, I had forgotten about that. I installed the attached patch, 
which changes FOR_EACH_TAIL to act more like these other macros. That 
is. FOR_EACH_TAIL (tail) now updates 'tail' each time through the loop, 
and the caller needs to declare the 'tail' variable outside the loop; 
this is as it was before.