Re: atomic accesses

[rridge at csclub dot uwaterloo dot ca (Ross Ridge)]

Segher Boessenkool writes:
>... People are relying on this undocumented GCC behaviour already,
>and when things break, chaos ensues.

GCC has introduced many changes over the years that have broken many
programs that have relied on undocumented or unspecified behaviour.
You won't find much sympathy for who people assume that GCC must behave
in some way where there is no requirement for it to do so. 

>If we change this to be documented behaviour, at least it is clear
>where the problem lies (namely, with the compiler), and things can be
>fixed easily.

I don't think you'll find any support for imposing a requirement on GCC
that would always require it to use an "atomic" instruction when there
is alternative instruction or sequence of instructions that would be
faster and/or shorter.  I think your best bet a long these lines would
be adding __sync_fetch() and __sync_store() builtins, but doing so would
be more difficult than a simple documentation change.

					Ross Ridge