commit 08bbce9923aec1eee0e6879c198b06c1b8f87d35
Author:     Jacob Welsh <jfw>
AuthorDate: Mon Oct 27 16:44:23 2025 +0000
Commit:     Jacob Welsh <jfw>
CommitDate: Tue Oct 28 01:16:53 2025 +0000

    busybox: use volatile sig_atomic_t for global written from signal handler, per standard C.
    
    This could fix a theoretical optimization-dependent situation where an applet fails to detect a signal because bb_got_signal isn't refreshed from memory.
    
    Previously noted in: http://jfxpt.com/2022/busybox-microcom-the-code-review/
    
    Text size +18 bytes on amd64, Gales configuration.

diff --git a/base/busybox/include/libbb.h b/base/busybox/include/libbb.h
index a08b3e1..8ef87b7 100644
--- a/base/busybox/include/libbb.h
+++ b/base/busybox/include/libbb.h
@@ -482,7 +482,7 @@ int sigaction_set(int sig, const struct sigaction *act) FAST_FUNC;
 /* SIG_BLOCK/SIG_UNBLOCK all signals: */
 int sigprocmask_allsigs(int how) FAST_FUNC;
 /* Standard handler which just records signo */
-extern smallint bb_got_signal;
+extern volatile sig_atomic_t bb_got_signal;
 void record_signo(int signo); /* not FAST_FUNC! */
 
 
diff --git a/base/busybox/init/init.c b/base/busybox/init/init.c
index 80c5d0f..634168d 100644
--- a/base/busybox/init/init.c
+++ b/base/busybox/init/init.c
@@ -866,7 +866,7 @@ static void exec_restart_action(void)
  */
 static void stop_handler(int sig UNUSED_PARAM)
 {
-	smallint saved_bb_got_signal;
+	int saved_bb_got_signal;
 	int saved_errno;
 
 	saved_bb_got_signal = bb_got_signal;
@@ -959,7 +959,7 @@ static int check_delayed_sigs(void)
 	int sigs_seen = 0;
 
 	while (1) {
-		smallint sig = bb_got_signal;
+		int sig = bb_got_signal;
 
 		if (!sig)
 			return sigs_seen;
diff --git a/base/busybox/libbb/signals.c b/base/busybox/libbb/signals.c
index 5651247..d7eb849 100644
--- a/base/busybox/libbb/signals.c
+++ b/base/busybox/libbb/signals.c
@@ -11,8 +11,8 @@
 
 #include "libbb.h"
 
-/* All known arches use small ints for signals */
-smallint bb_got_signal;
+/* Was smallint (not even volatile) because "all known arches use small ints for signals". Be that as it may, it seems a weak support for venturing into undefined behavior per C89. */
+volatile sig_atomic_t bb_got_signal;
 
 void record_signo(int signo)
 {