[cfe-dev] User manual, and GCC functions not implemented

[Jeffrey Walton]

http://clang.llvm.org/docs/UsersManual.html#gcc-extensions-not-implemented-yet

"clang does not support nested functions; this is a complex feature..."

That is bitter sweet. I need it because a library I'm building uses
them (but I'd prefer the library not use them).

The devs might consider adding text to the statements: in addition to
being complex, it also breaks No-Exec Stacks because a trampoline is
placed on the stack (assuming Clang would have a similar
implementation to GCC). I think the security posture is more important
than feature complexity ;)

And the devs might consider adding this text to the statements: Clang
has no plans to implement the feature. See Bug 6378,
http://www.llvm.org/bugs/show_bug.cgi?id=6378.