[Bug other/59039] New: Undocumented __builtin_longjmp/__builtin_setjmp

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59039

            Bug ID: 59039
           Summary: Undocumented __builtin_longjmp/__builtin_setjmp
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com

cilk_fiber-unix.cpp has

#pragma GCC push_options
#pragma GCC optimize ("-O0")
NORETURN cilk_fiber_sysdep::run()
{

It fails when compiled with any optimization.  This function has
__builtin_setjmp and __builtin_longjmp within the same function.
When __builtin_longjmp is put in a separate function, optimization
works.  But there is no documentation on how __builtin_longjmp
and __builtin_setjmp should be used, like the jump buffer size
and fields as well as any limitation.

If it is true that __builtin_setjmp and __builtin_longjmp can't be
used within the same function, GCC should issue an error, at least
a warning.