iUse sigaction(SA_NOCLDWAIT) for SIGCHLD handling - dwm - dynamic window manager	Err	parazyd.org	70
hgit clone https://git.parazyd.org/dwm	URL:https://git.parazyd.org/dwm	parazyd.org	70
1Log	/git/dwm/log.gph	parazyd.org	70
1Files	/git/dwm/files.gph	parazyd.org	70
1Refs	/git/dwm/refs.gph	parazyd.org	70
1README	/git/dwm/file/README.gph	parazyd.org	70
1LICENSE	/git/dwm/file/LICENSE.gph	parazyd.org	70
i---	Err	parazyd.org	70
1commit 712d6639ff8e863560328131bbb92b248dc9cde7	/git/dwm/commit/712d6639ff8e863560328131bbb92b248dc9cde7.gph	parazyd.org	70
1parent 89f9905714c1c1b2e8b09986dfbeca15b68d8af8	/git/dwm/commit/89f9905714c1c1b2e8b09986dfbeca15b68d8af8.gph	parazyd.org	70
hAuthor: Chris Down <chris@chrisdown.name>	URL:mailto:chris@chrisdown.name	parazyd.org	70
iDate:   Sat, 28 Jan 2023 12:53:48 +0100	Err	parazyd.org	70
i	Err	parazyd.org	70
iUse sigaction(SA_NOCLDWAIT) for SIGCHLD handling	Err	parazyd.org	70
i	Err	parazyd.org	70
isignal() semantics are pretty unclearly specified. For example, depending on OS	Err	parazyd.org	70
ikernel and libc, the handler may be returned to SIG_DFL (hence the inner call	Err	parazyd.org	70
ito read the signal handler). Moving to sigaction() means the behaviour is	Err	parazyd.org	70
iconsistently defined.	Err	parazyd.org	70
i	Err	parazyd.org	70
iUsing SA_NOCLDWAIT also allows us to avoid calling the non-reentrant function	Err	parazyd.org	70
idie() in the handler.	Err	parazyd.org	70
i	Err	parazyd.org	70
iSome addditional notes for archival purposes:	Err	parazyd.org	70
i	Err	parazyd.org	70
i* NRK pointed out errno of waitpid could also theoretically get clobbered.	Err	parazyd.org	70
i* The original patch was iterated on and modified by NRK and Hiltjo:	Err	parazyd.org	70
i  * SIG_DFL was changed to SIG_IGN, this is required, atleast on older systems	Err	parazyd.org	70
i    such as tested on Slackware 11.	Err	parazyd.org	70
i  * signals are not blocked using sigprocmask, because in theory it would	Err	parazyd.org	70
i    briefly for example also ignore a SIGTERM signal. It is OK if waitpid() is (in	Err	parazyd.org	70
i    theory interrupted).	Err	parazyd.org	70
i	Err	parazyd.org	70
iPOSIX reference:	Err	parazyd.org	70
i"Consequences of Process Termination":	Err	parazyd.org	70
ihttps://pubs.opengroup.org/onlinepubs/9699919799/functions/_Exit.html#tag_16_01_03_01	Err	parazyd.org	70
i	Err	parazyd.org	70
iDiffstat:	Err	parazyd.org	70
i  M dwm.c                               |      20 +++++++++-----------	Err	parazyd.org	70
i	Err	parazyd.org	70
i1 file changed, 9 insertions(+), 11 deletions(-)	Err	parazyd.org	70
i---	Err	parazyd.org	70
1diff --git a/dwm.c b/dwm.c	/git/dwm/file/dwm.c.gph	parazyd.org	70
i@@ -205,7 +205,6 @@ static void setmfact(const Arg *arg);	Err	parazyd.org	70
i static void setup(void);	Err	parazyd.org	70
i static void seturgent(Client *c, int urg);	Err	parazyd.org	70
i static void showhide(Client *c);	Err	parazyd.org	70
i-static void sigchld(int unused);	Err	parazyd.org	70
i static void spawn(const Arg *arg);	Err	parazyd.org	70
i static void tag(const Arg *arg);	Err	parazyd.org	70
i static void tagmon(const Arg *arg);	Err	parazyd.org	70
i@@ -1543,9 +1542,16 @@ setup(void)	Err	parazyd.org	70
i         int i;	Err	parazyd.org	70
i         XSetWindowAttributes wa;	Err	parazyd.org	70
i         Atom utf8string;	Err	parazyd.org	70
i+        struct sigaction sa;	Err	parazyd.org	70
i 	Err	parazyd.org	70
i-        /* clean up any zombies immediately */	Err	parazyd.org	70
i-        sigchld(0);	Err	parazyd.org	70
i+        /* do not transform children into zombies when they terminate */	Err	parazyd.org	70
i+        sigemptyset(&sa.sa_mask);	Err	parazyd.org	70
i+        sa.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT | SA_RESTART;	Err	parazyd.org	70
i+        sa.sa_handler = SIG_IGN;	Err	parazyd.org	70
i+        sigaction(SIGCHLD, &sa, NULL);	Err	parazyd.org	70
i+	Err	parazyd.org	70
i+        /* clean up any zombies (inherited from .xinitrc etc) immediately */	Err	parazyd.org	70
i+        while (waitpid(-1, NULL, WNOHANG) > 0);	Err	parazyd.org	70
i 	Err	parazyd.org	70
i         /* init screen */	Err	parazyd.org	70
i         screen = DefaultScreen(dpy);	Err	parazyd.org	70
i@@ -1639,14 +1645,6 @@ showhide(Client *c)	Err	parazyd.org	70
i }	Err	parazyd.org	70
i 	Err	parazyd.org	70
i void	Err	parazyd.org	70
i-sigchld(int unused)	Err	parazyd.org	70
i-{	Err	parazyd.org	70
i-        if (signal(SIGCHLD, sigchld) == SIG_ERR)	Err	parazyd.org	70
i-                die("can't install SIGCHLD handler:");	Err	parazyd.org	70
i-        while (0 < waitpid(-1, NULL, WNOHANG));	Err	parazyd.org	70
i-}	Err	parazyd.org	70
i-	Err	parazyd.org	70
i-void	Err	parazyd.org	70
i spawn(const Arg *arg)	Err	parazyd.org	70
i {	Err	parazyd.org	70
i         if (arg->v == dmenucmd)	Err	parazyd.org	70
.