Re: [bug-gawk] coprocess pseudo-tty bug

[arnold]

address@hidden wrote:

> Root cause is that Linux requires the slave to be opened and configured
> in the parent, before the child process is forked.
>
> AIX can't hack that, which is what broke Linux. It's gonna take a
> more serious fix, which I'll work on over the next day or so.

Fix is below.

Thanks,

Arnold
-----------------------------------
diff --git a/io.c b/io.c
index 7314d8e..7a0151b 100644
--- a/io.c
+++ b/io.c
@@ -1892,6 +1892,233 @@ strictopen:
        return openfd;
 }
 
+/* fork_and_open_slave_pty --- handle forking the child and slave pty setup */
+
+/*
+ * January, 2018:
+ * This is messy. AIX and HP-UX require that the slave pty be opened and
+ * set up in the child.  Everything else wants it to be done in the parent,
+ * before the fork.  Thus we have two different versions of the routine that
+ * do the same thing, but in different orders.  This is not pretty, but it
+ * seems to be the simplest thing to do.
+ */
+
+#if defined _AIX || defined __hpux
+static bool
+fork_and_open_slave_pty(const char *slavenam, int master, const char *command, 
pid_t *pid)
+{
+       struct termios st;
+       int slave;
+       int save_errno;
+
+       /*
+        * We specifically open the slave only in the child. This allows
+        * certain, er, "limited" systems to work.  The open is specifically
+        * without O_NOCTTY in order to make the slave become the controlling
+        * terminal.
+        */
+
+       switch (*pid = fork()) {
+       case 0:
+               /* Child process */
+               setsid();
+
+               if ((slave = open(slavenam, O_RDWR)) < 0) {
+                       close(master);
+                       fatal(_("could not open `%s', mode `%s'"),
+                               slavenam, "r+");
+               }
+
+#ifdef I_PUSH
+               /*
+                * Push the necessary modules onto the slave to
+                * get terminal semantics.  Check that they aren't
+                * already there to avoid hangs on said "limited" systems.
+                */
+#ifdef I_FIND
+               if (ioctl(slave, I_FIND, "ptem") == 0)
+#endif
+                       ioctl(slave, I_PUSH, "ptem");
+#ifdef I_FIND
+               if (ioctl(slave, I_FIND, "ldterm") == 0)
+#endif
+                       ioctl(slave, I_PUSH, "ldterm");
+#endif
+               tcgetattr(slave, & st);
+
+               st.c_iflag &= ~(ISTRIP | IGNCR | INLCR | IXOFF);
+               st.c_iflag |= (ICRNL | IGNPAR | BRKINT | IXON);
+               st.c_oflag &= ~OPOST;
+               st.c_cflag &= ~CSIZE;
+               st.c_cflag |= CREAD | CS8 | CLOCAL;
+               st.c_lflag &= ~(ECHO | ECHOE | ECHOK | NOFLSH | TOSTOP);
+               st.c_lflag |= ISIG;
+
+               /* Set some control codes to default values */
+#ifdef VINTR
+               st.c_cc[VINTR] = '\003';        /* ^c */
+#endif
+#ifdef VQUIT
+               st.c_cc[VQUIT] = '\034';        /* ^| */
+#endif
+#ifdef VERASE
+               st.c_cc[VERASE] = '\177';       /* ^? */
+#endif
+#ifdef VKILL
+               st.c_cc[VKILL] = '\025';        /* ^u */
+#endif
+#ifdef VEOF
+               st.c_cc[VEOF] = '\004'; /* ^d */
+#endif
+
+#ifdef TIOCSCTTY
+               /*
+                * This may not necessary anymore given that we
+                * open the slave in the child, but it doesn't hurt.
+                */
+               ioctl(slave, TIOCSCTTY, 0);
+#endif
+               tcsetattr(slave, TCSANOW, & st);
+
+               if (close(master) == -1)
+                       fatal(_("close of master pty failed (%s)"), 
strerror(errno));
+               if (close(1) == -1)
+                       fatal(_("close of stdout in child failed (%s)"),
+                               strerror(errno));
+               if (dup(slave) != 1)
+                       fatal(_("moving slave pty to stdout in child failed 
(dup: %s)"), strerror(errno));
+               if (close(0) == -1)
+                       fatal(_("close of stdin in child failed (%s)"),
+                               strerror(errno));
+               if (dup(slave) != 0)
+                       fatal(_("moving slave pty to stdin in child failed 
(dup: %s)"), strerror(errno));
+               if (close(slave))
+                       fatal(_("close of slave pty failed (%s)"), 
strerror(errno));
+
+               /* stderr does NOT get dup'ed onto child's stdout */
+
+               set_sigpipe_to_default();
+
+               execl("/bin/sh", "sh", "-c", command, NULL);
+               _exit(errno == ENOENT ? 127 : 126);
+
+       case -1:
+               save_errno = errno;
+               close(master);
+               errno = save_errno;
+               return false;
+
+       default:
+               return true;
+       }
+}
+#else
+static bool
+fork_and_open_slave_pty(const char *slavenam, int master, const char *command, 
pid_t *pid)
+{
+       struct termios st;
+       int slave;
+       int save_errno;
+
+       if ((slave = open(slavenam, O_RDWR)) < 0) {
+               close(master);
+               fatal(_("could not open `%s', mode `%s'"),
+                       slavenam, "r+");
+       }
+
+#ifdef I_PUSH
+       /*
+        * Push the necessary modules onto the slave to
+        * get terminal semantics.
+        */
+#ifdef I_FIND
+       if (ioctl(slave, I_FIND, "ptem") == 0)
+#endif
+               ioctl(slave, I_PUSH, "ptem");
+#ifdef I_FIND
+       if (ioctl(slave, I_FIND, "ldterm") == 0)
+#endif
+               ioctl(slave, I_PUSH, "ldterm");
+#endif
+
+       tcgetattr(slave, & st);
+       st.c_iflag &= ~(ISTRIP | IGNCR | INLCR | IXOFF);
+       st.c_iflag |= (ICRNL | IGNPAR | BRKINT | IXON);
+       st.c_oflag &= ~OPOST;
+       st.c_cflag &= ~CSIZE;
+       st.c_cflag |= CREAD | CS8 | CLOCAL;
+       st.c_lflag &= ~(ECHO | ECHOE | ECHOK | NOFLSH | TOSTOP);
+       st.c_lflag |= ISIG;
+
+       /* Set some control codes to default values */
+#ifdef VINTR
+       st.c_cc[VINTR] = '\003';        /* ^c */
+#endif
+#ifdef VQUIT
+       st.c_cc[VQUIT] = '\034';        /* ^| */
+#endif
+#ifdef VERASE
+       st.c_cc[VERASE] = '\177';       /* ^? */
+#endif
+#ifdef VKILL
+       st.c_cc[VKILL] = '\025';        /* ^u */
+#endif
+#ifdef VEOF
+       st.c_cc[VEOF] = '\004'; /* ^d */
+#endif
+       tcsetattr(slave, TCSANOW, & st);
+
+       switch (*pid = fork()) {
+       case 0:
+               /* Child process */
+               setsid();
+
+#ifdef TIOCSCTTY
+               ioctl(slave, TIOCSCTTY, 0);
+#endif
+
+               if (close(master) == -1)
+                       fatal(_("close of master pty failed (%s)"), 
strerror(errno));
+               if (close(1) == -1)
+                       fatal(_("close of stdout in child failed (%s)"),
+                               strerror(errno));
+               if (dup(slave) != 1)
+                       fatal(_("moving slave pty to stdout in child failed 
(dup: %s)"), strerror(errno));
+               if (close(0) == -1)
+                       fatal(_("close of stdin in child failed (%s)"),
+                               strerror(errno));
+               if (dup(slave) != 0)
+                       fatal(_("moving slave pty to stdin in child failed 
(dup: %s)"), strerror(errno));
+               if (close(slave))
+                       fatal(_("close of slave pty failed (%s)"), 
strerror(errno));
+
+               /* stderr does NOT get dup'ed onto child's stdout */
+
+               signal(SIGPIPE, SIG_DFL);
+
+               execl("/bin/sh", "sh", "-c", command, NULL);
+               _exit(errno == ENOENT ? 127 : 126);
+
+       case -1:
+               save_errno = errno;
+               close(master);
+               close(slave);
+               errno = save_errno;
+               return false;
+
+       }
+
+       /* parent */
+       if (close(slave) != 0) {
+               close(master);
+               (void) kill(*pid, SIGKILL);
+               fatal(_("close of slave pty failed (%s)"), strerror(errno));
+       }
+
+       return true;
+}
+#endif
+
 /* two_way_open --- open a two way communications channel */
 
 static int
@@ -1955,11 +2182,8 @@ two_way_open(const char *str, struct redirect *rp, int 
extfd)
                char slavenam[32];
                char c;
                int master, dup_master;
-               int slave;
-               int save_errno;
                pid_t pid;
                struct stat statb;
-               struct termios st;
                /* Use array of chars to avoid ASCII / EBCDIC issues */
                static char pty_chars[] = "pqrstuvwxyzabcdefghijklmno";
                int i;
@@ -2046,104 +2270,9 @@ two_way_open(const char *str, struct redirect *rp, int 
extfd)
 
        got_the_pty:
 
-               /*
-                * We specifically open the slave only in the child. This allows
-                * certain, er, "limited" systems to work.  The open is 
specifically
-                * without O_NOCTTY in order to make the slave become the 
controlling
-                * terminal.
-                */
-
-               switch (pid = fork()) {
-               case 0:
-                       /* Child process */
-                       setsid();
-
-                       if ((slave = open(slavenam, O_RDWR)) < 0) {
-                               close(master);
-                               fatal(_("could not open `%s', mode `%s'"),
-                                       slavenam, "r+");
-                       }
-
-#ifdef I_PUSH
-                       /*
-                        * Push the necessary modules onto the slave to
-                        * get terminal semantics.  Check that they aren't
-                        * already there to avoid hangs on said "limited" 
systems.
-                        */
-#ifdef I_FIND
-                       if (ioctl(slave, I_FIND, "ptem") == 0)
-#endif
-                               ioctl(slave, I_PUSH, "ptem");
-#ifdef I_FIND
-                       if (ioctl(slave, I_FIND, "ldterm") == 0)
-#endif
-                               ioctl(slave, I_PUSH, "ldterm");
-#endif
-                       tcgetattr(slave, & st);
-
-                       st.c_iflag &= ~(ISTRIP | IGNCR | INLCR | IXOFF);
-                       st.c_iflag |= (ICRNL | IGNPAR | BRKINT | IXON);
-                       st.c_oflag &= ~OPOST;
-                       st.c_cflag &= ~CSIZE;
-                       st.c_cflag |= CREAD | CS8 | CLOCAL;
-                       st.c_lflag &= ~(ECHO | ECHOE | ECHOK | NOFLSH | TOSTOP);
-                       st.c_lflag |= ISIG;
-
-                       /* Set some control codes to default values */
-#ifdef VINTR
-                       st.c_cc[VINTR] = '\003';        /* ^c */
-#endif
-#ifdef VQUIT
-                       st.c_cc[VQUIT] = '\034';        /* ^| */
-#endif
-#ifdef VERASE
-                       st.c_cc[VERASE] = '\177';       /* ^? */
-#endif
-#ifdef VKILL
-                       st.c_cc[VKILL] = '\025';        /* ^u */
-#endif
-#ifdef VEOF
-                       st.c_cc[VEOF] = '\004'; /* ^d */
-#endif
-
-#ifdef TIOCSCTTY
-                       /*
-                        * This may not necessary anymore given that we
-                        * open the slave in the child, but it doesn't hurt.
-                        */
-                       ioctl(slave, TIOCSCTTY, 0);
-#endif
-                       tcsetattr(slave, TCSANOW, & st);
-
-                       if (close(master) == -1)
-                               fatal(_("close of master pty failed (%s)"), 
strerror(errno));
-                       if (close(1) == -1)
-                               fatal(_("close of stdout in child failed (%s)"),
-                                       strerror(errno));
-                       if (dup(slave) != 1)
-                               fatal(_("moving slave pty to stdout in child 
failed (dup: %s)"), strerror(errno));
-                       if (close(0) == -1)
-                               fatal(_("close of stdin in child failed (%s)"),
-                                       strerror(errno));
-                       if (dup(slave) != 0)
-                               fatal(_("moving slave pty to stdin in child 
failed (dup: %s)"), strerror(errno));
-                       if (close(slave))
-                               fatal(_("close of slave pty failed (%s)"), 
strerror(errno));
-
-                       /* stderr does NOT get dup'ed onto child's stdout */
-
-                       set_sigpipe_to_default();
-
-                       execl("/bin/sh", "sh", "-c", str, NULL);
-                       _exit(errno == ENOENT ? 127 : 126);
-
-               case -1:
-                       save_errno = errno;
-                       close(master);
-                       errno = save_errno;
-                       return false;
-
-               }
+               /* this is the parent */
+               if (! fork_and_open_slave_pty(slavenam, master, str, & pid))
+                       fatal(_("could not create child process or open pty"));
 
                rp->pid = pid;
                rp->iop = iop_alloc(master, str, 0);