On Tue, 3 Apr 2018, Zack Weinberg wrote: > On Tue, Apr 3, 2018 at 5:58 PM, Samuel Thibault <samuel.thiba...@gnu.org> > wrote: > > Joseph Myers, on mar. 03 avril 2018 21:48:32 +0000, wrote: > >> The build for i686-gnu also fails using GCC 6 branch with > >> build-many-glibcs.py: > >> > >> hurdsig.c: In function 'interrupted_reply_port_location.isra.1': > >> hurdsig.c:250:39: error: 'portloc' may be used uninitialized in this > >> function [-Werror=maybe-uninitialized] > >> *(volatile mach_port_t *) portloc = *portloc; > >> ^~~~~~~~ > >> > >> I haven't investigated whether this warning is valid, or whether it's > >> bogus > > > > Well, it's completely bogus: portloc is initialized just above. I don't > > understand why it wouldn't see that. > > I think it thinks the *value pointed-to by portloc* is uninitialized.
This is just after a call to _hurdsig_catch_memory_fault, which is a macro involving a call to setjmp. I think the returns-twice nature of setjmp is confusing the compiler into thinking portloc itself is uninitialized (I don't know why this particular warning) - in fact, the second return of setjmp will never reach the code getting the warning (as setjmp will return nonzero, so _hurdsig_catch_memory_fault will). -- Joseph S. Myers jos...@codesourcery.com
