[git commit] ash: prevent error in backquotes in PS1 from exiting shell

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=48645b83502a5add5429b6cbb19cf3a083f1adf4
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

Setting PS1 to:

   PS1='`xxx(`'

causes the shell to terminate with the error:

   sh: syntax error: unexpected end of file (expecting ")")

This happens because old-style backquotes require the input to be reread
and thus call setinputstring() a second time.  Prevent the problem by
unwinding all recently opened files in expandstr().

function                                             old     new   delta
unwindfiles                                            -      22     +22
expandstr                                            247     262     +15
forkchild                                            631     625      -6
evalcommand                                         1694    1685      -9
ash_main                                            1346    1336     -10
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/3 up/down: 37/-25)             Total: 12 bytes

Signed-off-by: Ron Yorston <rmy at pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 shell/ash.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/shell/ash.c b/shell/ash.c
index b707d00d0..f3a2c6952 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -13042,6 +13042,7 @@ expandstr(const char *ps, int syntax_type)
 {
 	union node n;
 	int saveprompt;
+	struct parsefile *file_stop = g_parsefile;
 
 	/* XXX Fix (char *) cast. */
 	setinputstring((char *)ps);
@@ -13068,7 +13069,8 @@ expandstr(const char *ps, int syntax_type)
 
 	doprompt = saveprompt;
 
-	popfile();
+	/* Try: PS1='`xxx(`' */
+	unwindfiles(file_stop);
 
 	n.narg.type = NARG;
 	n.narg.next = NULL;