overhaul implementation-internal signal protections

the new approach relies on the fact that the only ways to create
sigset_t objects without invoking UB are to use the sig*set()
functions, or from the masks returned by sigprocmask, sigaction, etc.
or in the ucontext_t argument to a signal handler. thus, as long as
sigfillset and sigaddset avoid adding the "protected" signals, there
is no way the application will ever obtain a sigset_t including these
bits, and thus no need to add the overhead of checking/clearing them
when sigprocmask or sigaction is called.

note that the old code actually *failed* to remove the bits from
sa_mask when sigaction was called.

the new implementations are also significantly smaller, simpler, and
faster due to ignoring the useless "GNU HURD signals" 65-1024, which
are not used and, if there's any sanity in the world, never will be
used.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/signal/sigemptyset.c b/src/signal/sigemptyset.c
index 91f77adf..ca9b8920 100644
--- a/src/signal/sigemptyset.c
+++ b/src/signal/sigemptyset.c
@@ -3,6 +3,7 @@
 
 int sigemptyset(sigset_t *set)
 {
-	memset(set, 0, sizeof *set);
+	set->__bits[0] = 0;
+	if (sizeof(long)==4) set->__bits[1] = 0;
 	return 0;
 }