*: introduce and use xvfork()

function                                             old     new   delta
time_main                                           1052    1285    +233
crontab_main                                         623     856    +233
ifupdown_main                                       2202    2403    +201
xvfork                                                 -      20     +20
passwd_main                                         1049    1053      +4
grave                                               1068    1066      -2
script_main                                          935     921     -14
vfork_or_die                                          20       -     -20
vfork_compressor                                     206     175     -31
open_as_user                                         109       -    -109
popen2                                               218       -    -218
edit_file                                            910     690    -220
run_command                                          268       -    -268
------------------------------------------------------------------------------
(add/remove: 1/4 grow/shrink: 4/4 up/down: 691/-882)         Total: -191 bytes

2 files changed, 2 insertions, 6 deletions

diff --git a/archival/libunarchive/open_transformer.c b/archival/libunarchive/open_transformer.c
index a6bc62321..16ca6a59c 100644
--- a/archival/libunarchive/open_transformer.c
+++ b/archival/libunarchive/open_transformer.c
@@ -25,9 +25,7 @@ int FAST_FUNC open_transformer(int src_fd,
         if (pid == -1)
                 bb_perror_msg_and_die("can't fork");
 #else
-        pid = vfork();
-        if (pid == -1)
-                bb_perror_msg_and_die("can't vfork");
+        pid = xvfork();
 #endif
 
         if (pid == 0) {
diff --git a/archival/tar.c b/archival/tar.c
index 526edb69d..17ac6c55a 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -536,9 +536,7 @@ static void NOINLINE vfork_compressor(int tar_fd, int gzip)
         (void) &zip_exec;
 #endif
 
-        gzipPid = vfork();
-        if (gzipPid < 0)
-                bb_perror_msg_and_die("can't vfork");
+        gzipPid = xvfork();
 
         if (gzipPid == 0) {
                 /* child */