ash: don't initialise shell variables in forkshell child

The forkshell child process calls init(), which mostly just initialises
shell variables.  Since these variables are overwritten with values from
the parent process there's no point in doing that.

In particular, init() initialises HOSTNAME by calling gethostname()
which involves network access and is slow.  Avoid this cost when
we know the shell is a forkshell child.

1 files changed, 9 insertions, 2 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 4a075d1ea..f57819810 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -14989,11 +14989,11 @@ static void xsetenv_if_unset(const char *key, const char *value)
 static NOINLINE void
 init(void)
 {
+#if !ENABLE_PLATFORM_MINGW32
         /* we will never free this */
         basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ);
         basepf.linno = 1;
 
-#if !ENABLE_PLATFORM_MINGW32
         sigmode[SIGCHLD - 1] = S_DFL; /* ensure we install handler even if it is SIG_IGNed */
         setsignal(SIGCHLD);
 #endif
@@ -15254,6 +15254,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         int login_sh;
 #if ENABLE_PLATFORM_MINGW32
         char *sd;
+        int is_forkshell;
 #endif
 
         /* Initialize global data */
@@ -15302,7 +15303,13 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         rootpid = getpid();
 
 #if ENABLE_PLATFORM_MINGW32
+        /* we will never free this */
+        basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ);
+        basepf.linno = 1;
+
         winxp = (argv[1] != NULL && strcmp(argv[1], "-X") == 0);
+        is_forkshell = (argc == 3 && !strcmp(argv[1], "--fs"));
+        if (!is_forkshell)
 #endif
         init();
         setstackmark(&smark);
@@ -15311,7 +15318,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         hSIGINT = CreateEvent(NULL, TRUE, FALSE, NULL);
         SetConsoleCtrlHandler(ctrl_handler, TRUE);
 
-        if (argc == 3 && !strcmp(argv[1], "--fs")) {
+        if (is_forkshell) {
                 forkshell_init(argv[2]);
 
                 /* only reached in case of error */