ash: eval: Do not cache value of eflag in evaltree

Upsteam commit:

    Date: Mon, 17 May 2021 15:19:23 +0800
    eval: Do not cache value of eflag in evaltree

    Patrick Brünn <P.Bruenn@beckhoff.com> wrote:
    > Since we are migrating to Debian bullseye, we discovered a new behavior
    > with our scripts, which look like this:
    >>cleanup() {
    >>        set +e
    >>        rmdir ""
    >>}
    >>set -eu
    >>trap 'cleanup' EXIT INT TERM
    >>echo 'Hello world!'
    >
    > With old dash v0.5.10.2 this script would return 0 as we expected it.
    > But since commit 62cf6955f8abe875752d7163f6f3adbc7e49ebae it returns
    > the last exit code of our cleanup function.
    ...
    Thanks for the report.  This is actually a fairly old bug with
    set -e that's just been exposed by the exit status change.  What's
    really happening is that cleanup itself is triggering a set -e
    exit incorrectly because evaltree cached the value of eflag prior
    to the function call.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 16 insertions, 8 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 2d2c09ba5..c65f09782 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -9336,8 +9336,7 @@ evaltree(union node *n, int flags)
         case NCMD:
                 evalfn = evalcommand;
  checkexit:
-                if (!(flags & EV_TESTED))
-                        checkexit = ~0;
+                checkexit = ~flags & EV_TESTED;
                 goto calleval;
         case NFOR:
                 evalfn = evalfor;
@@ -9359,7 +9358,6 @@ evaltree(union node *n, int flags)
         case NAND:
         case NOR:
         case NSEMI: {
-
 #if NAND + 1 != NOR
 #error NAND + 1 != NOR
 #endif
@@ -9387,8 +9385,7 @@ evaltree(union node *n, int flags)
                 if (!status) {
                         n = n->nif.ifpart;
                         goto evaln;
-                }
-                if (n->nif.elsepart) {
+                } else if (n->nif.elsepart) {
                         n = n->nif.elsepart;
                         goto evaln;
                 }
@@ -9410,7 +9407,7 @@ evaltree(union node *n, int flags)
          */
         dotrap();
 
-        if (checkexit & status) {
+        if (checkexit && status) {
                 if (trap[NTRAP_ERR] && !in_trap_ERR) {
                         int err;
                         struct jmploc *volatile savehandler = exception_handler;
@@ -9434,10 +9431,12 @@ evaltree(union node *n, int flags)
                         exitstatus = savestatus;
                 }
                 if (eflag)
-                        raise_exception(EXEND);
+                        goto exexit;
         }
-        if (flags & EV_EXIT)
+        if (flags & EV_EXIT) {
+ exexit:
                 raise_exception(EXEND);
+        }
 
         popstackmark(&smark);
         TRACE(("leaving evaltree (no interrupts)\n"));
diff --git a/shell/ash_test/ash-misc/exitcode_trap7.right b/shell/ash_test/ash-misc/exitcode_trap7.right
new file mode 100644
index 000000000..07d66e9d9
--- /dev/null
+++ b/shell/ash_test/ash-misc/exitcode_trap7.right
@@ -0,0 +1,2 @@
+Start
+Ok:0
diff --git a/shell/ash_test/ash-misc/exitcode_trap7.tests b/shell/ash_test/ash-misc/exitcode_trap7.tests
new file mode 100755
index 000000000..9772a7b8c
--- /dev/null
+++ b/shell/ash_test/ash-misc/exitcode_trap7.tests
@@ -0,0 +1,7 @@
+$THIS_SH -c '
+cleanup() { set +e; false; }
+set -eu
+trap cleanup EXIT
+echo Start
+'
+echo Ok:$?