[Bug c/69982] missing warning when using __thread with -std=c99 -pedantic

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69982

--- Comment #3 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Jakub Jelinek from comment #2)
> [...] and __thread uses the implementation namespace, [...]

Is this really the implementation namespace?

The C standard says: "All identifiers that begin with an underscore and either
an uppercase letter or another underscore are always reserved for any use." so
that there doesn't seem to be a difference between __thread (underscore +
underscore) and _Thread_local (underscore + uppercase letter).

What if the C committee decided to choose __thread instead of _Thread_local?