[st][PATCH] externalpipe sigaction

This patch should be applied on top of the externalpipe patch. It
prevents the reset of the signal handler set on SIGCHILD, when the
forked process that executes the external process exits. I opted for
switching from signal to sigaction instead of rearming the signal in the
sigchld function, just because it is the recommended function (although I
tried both ways and both worked).

README.md

@@ -15,7 +15,7 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
 
 ### Changelog:
 
-2020-04-20 - Added the force redraw on pselect after key is pressed patch
+2020-04-20 - Added the force redraw on pselect after key is pressed patch and the externalpipe sigaction patch
 
 2020-03-29 - Added invert and workingdir patches
 
@@ -60,6 +60,9 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
    - [externalpipe](https://st.suckless.org/patches/externalpipe/)
       - this patch allows for eading and writing st's screen through a pipe, e.g. to pass info to dmenu
 
+   - [externalpipe-sigaction](https://lists.suckless.org/hackers/2004/17216.html)
+      - this patch prevents the reset of the signal handler set on SIGCHILD, when the forked process that executes the external process exits
+
    - [~fixime~](https://st.suckless.org/patches/fix_ime/)
       - adds better Input Method Editor (IME) support
       - (included in the base as per [35f7db](https://git.suckless.org/st/commit/e85b6b64660214121164ea97fb098eaa4935f7db.html))

patches.def.h

@@ -68,6 +68,13 @@
  */
 #define EXTERNALPIPE_PATCH 0
 
+/* This patch prevents the reset of the signal handler set on SIGCHILD, when
+ * the forked process that executes the external process exits.
+ * This patch depends on EXTERNALPIPE_PATCH being enabled.
+ * https://lists.suckless.org/hackers/2004/17216.html
+ */
+#define EXTERNALPIPE_SIGACTION_PATCH 0
+
 /* This patch allows command line applications to use all the fancy key combinations
  * that are available to GUI applications.
  * https://st.suckless.org/patches/fix_keyboard_input/

st.c

@@ -782,7 +782,11 @@ sigchld(int a)
 	int stat;
 	pid_t p;
 
+	#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+	if ((p = waitpid(-1, &stat, WNOHANG)) < 0)
+	#else
 	if ((p = waitpid(pid, &stat, WNOHANG)) < 0)
+	#endif // EXTERNALPIPE_SIGACTION_PATCH
 		die("waiting for pid %hd failed: %s\n", pid, strerror(errno));
 
 	if (pid != p)
@@ -823,6 +827,9 @@ int
 ttynew(char *line, char *cmd, char *out, char **args)
 {
 	int m, s;
+	#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+	struct sigaction sa;
+	#endif // EXTERNALPIPE_SIGACTION_PATCH
 
 	if (out) {
 		term.mode |= MODE_PRINT;
@@ -878,7 +885,14 @@ ttynew(char *line, char *cmd, char *out, char **args)
 #endif
 		close(s);
 		cmdfd = m;
+		#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+		memset(&sa, 0, sizeof(sa));
+		sigemptyset(&sa.sa_mask);
+		sa.sa_handler = sigchld;
+		sigaction(SIGCHLD, &sa, NULL);
+		#else
 		signal(SIGCHLD, sigchld);
+		#endif // EXTERNALPIPE_SIGACTION_PATCH
 		break;
 	}
 	return cmdfd;