Add xvfork() as a static inline and use it from various places.

Note: vfork(), like fork(), can return -1 if too many processes, and
we should notice and fail loudly.

6 files changed, 18 insertions, 6 deletions

diff --git a/lib/lib.h b/lib/lib.h
index 2b49dc17..cbac3aa5 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -246,5 +246,17 @@ void mode_to_string(mode_t mode, char *buf);
 char *basename_r(char *name);
 void names_to_pid(char **names, int (*callback)(pid_t pid, char *name));
 
+// Returning from a function can modify a potentially shared stack,
+// so this has to always inline.
+
+static inline pid_t xvfork(void)
+{
+  pid_t p = vfork();
+
+  if (p == -1) perror_exit("vfork");
+
+  return p;
+}
+
 // Functions in need of further review/cleanup
 #include "lib/pending.h"
diff --git a/toys/other/setsid.c b/toys/other/setsid.c
index 59a1d78f..83db044d 100644
--- a/toys/other/setsid.c
+++ b/toys/other/setsid.c
@@ -19,9 +19,9 @@ config SETSID
 
 void setsid_main(void)
 {
-  while (setsid()<0) if (vfork()) _exit(0);
+  while (setsid()<0) if (xvfork()) _exit(0);
   if (toys.optflags) {
-    setpgid(0,0);
+    setpgid(0, 0);
     tcsetpgrp(0, getpid());
   }
   xexec(toys.optargs);
diff --git a/toys/other/timeout.c b/toys/other/timeout.c
index 06b1e89a..bd716e63 100644
--- a/toys/other/timeout.c
+++ b/toys/other/timeout.c
@@ -62,7 +62,7 @@ void timeout_main(void)
   if (TT.s_signal && -1 == (TT.nextsig = sig_to_num(TT.s_signal)))
     error_exit("bad -s: '%s'", TT.s_signal);
 
-  if (!(TT.pid = xfork())) xexec(toys.optargs+1);
+  if (!(TT.pid = xvfork())) xexec(toys.optargs+1);
   else {
     int status;
 
diff --git a/toys/pending/sh.c b/toys/pending/sh.c
index 499c5dbd..87f2f9ff 100644
--- a/toys/pending/sh.c
+++ b/toys/pending/sh.c
@@ -305,7 +305,7 @@ static void run_pipeline(struct pipeline *line)
   } else {
     int status;
 
-    cmd->pid = vfork();
+    cmd->pid = xvfork();
     if (!cmd->pid) xexec(cmd->argv);
     else waitpid(cmd->pid, &status, 0);
 
diff --git a/toys/posix/time.c b/toys/posix/time.c
index 70d2997e..b3cfd26b 100644
--- a/toys/posix/time.c
+++ b/toys/posix/time.c
@@ -28,7 +28,7 @@ void time_main(void)
   struct timeval tv, tv2;
 
   gettimeofday(&tv, NULL);
-  if (!(pid = xfork())) xexec(toys.optargs);
+  if (!(pid = xvfork())) xexec(toys.optargs);
   else {
     int stat;
     struct rusage ru;
diff --git a/toys/posix/xargs.c b/toys/posix/xargs.c
index 8178bf0c..50c42620 100644
--- a/toys/posix/xargs.c
+++ b/toys/posix/xargs.c
@@ -168,7 +168,7 @@ void xargs_main(void)
     for (dtemp = dlist; dtemp; dtemp = dtemp->next)
       handle_entries(dtemp->data, out+entries);
 
-    pid_t pid=xfork();
+    pid_t pid=xvfork();
     if (!pid) {
       xclose(0);
       open("/dev/null", O_RDONLY);