[git commit branch/1_31_stable] ash: only catch unexpected exceptions in PS1 expansion

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=c88d3ec458e66d8c25af81ae7b2044933c069563
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/1_31_stable

Commit d1a2fa2a4 (ash: catch error in arithmetic expansion in PS1)
catches all exceptions raised by expandarg().  Some exceptions, such as
the EXEXIT raised when command expansion is used, are expected:

   export PS1='$(echo "$ ")'

These should be processed normally or the shell hangs at the prompt.

function                                             old     new   delta
expandstr                                            344     353      +9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 9/0)                 Total: 9 bytes

Signed-off-by: Ron Yorston <rmy at pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 shell/ash.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/shell/ash.c b/shell/ash.c
index e3bbac9a0..c0352602b 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -13126,6 +13126,8 @@ expandstr(const char *ps, int syntax_type)
 	if (setjmp(jmploc.loc) == 0) {
 		exception_handler = &jmploc;
 		expandarg(&n, NULL, EXP_QUOTED);
+	} else if (exception_type == EXEXIT) {
+		exitshell();
 	}
 	exception_handler = savehandler;
 	RESTORE_INT(saveint);