From 61e06f3b12afe464c3b4fcd23d4a3a07251c50ac Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Sat, 3 Sep 2022 10:22:33 +0000
Subject:  Include mitigation for BSD disease in sigaction wrapper

Signed-off-by: Laurent Bercot <ska@appnovation.com>
---
 src/libstddjb/sig_catch.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/libstddjb/sig_catch.c b/src/libstddjb/sig_catch.c
index 5195d4b..a11e317 100644
--- a/src/libstddjb/sig_catch.c
+++ b/src/libstddjb/sig_catch.c
@@ -2,14 +2,28 @@
 
 /* MT-unsafe */
 
+#include <skalibs/nonposix.h>
+#include <skalibs/bsdsnowflake.h>
+
 #include <signal.h>
+#include <errno.h>
 
 #include <skalibs/functypes.h>
 #include <skalibs/sig.h>
+#include <skalibs/nsig.h>
+
+ /*
+   BSD fails sigaction() with EINVAL on non-catchable signals, whereas
+   every reasonable OS succeeds and simply ignores the signal handler.
+ */
 
 int sig_catch (int sig, sig_func_ref f)
 {
   struct sigaction action = { .sa_handler = f, .sa_flags = SA_RESTART | SA_NOCLDSTOP } ;
   sigfillset(&action.sa_mask) ;
-  return sigaction(sig, &action, 0) >= 0 ;
+  return sigaction(sig, &action, 0) >= 0
+#ifdef SKALIBS_BSD_SUCKS
+ || (errno == EINVAL && sig >= 1 && sig <= NSIG)
+#endif
+ ;
 }
-- 
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