'case' zeroes "$?"

'case' zeroes "$?"

[Martijn Dekker]

Unlike on other shells, 'case' on zsh zeroes "$?" before executing a
command within 'case', making it more inconvenient to test exit status.

Example:

(exit 37) || case $? in 37) echo "$?";; esac

All shells except zsh and Busybox ash output 37; zsh outputs 0.
(dash recently fixed this: 0.5.8 outputs 0, 0.5.9.1 outputs 37.)

Thanks,

- Martijn

Re: 'case' zeroes "$?"

[Martijn Dekker]

Op 09-10-16 om 23:01 schreef Martijn Dekker:
> Example:
> 
> (exit 37) || case $? in 37) echo "$?";; esac
> 
> All shells except zsh and Busybox ash output 37; zsh outputs 0.

Actually, busybox ash just fixed this as well, see:
https://bugs.busybox.net/show_bug.cgi?id=9311
https://git.kernel.org/cgit/utils/dash/dash.git/commit/?id=da534b740e628512e8e0e62729d6a2ef521e5096

FreeBSD sh, another Almquist derivative, also outputs 37.

Thanks,

- M.

Re: 'case' zeroes "$?"

[Peter Stephenson]

On Sun, 9 Oct 2016 23:01:35 +0200
Martijn Dekker <martijn@inlv.org> wrote:
> Unlike on other shells, 'case' on zsh zeroes "$?" before executing a
> command within 'case', making it more inconvenient to test exit status.
> 
> Example:
> 
> (exit 37) || case $? in 37) echo "$?";; esac

This looks straightforward.  The first $? in the case pattern is expanded
as a command line argument, before the case is executed, so missed this.

diff --git a/Src/loop.c b/Src/loop.c
index 3b9d021..94b61b7 100644
--- a/Src/loop.c
+++ b/Src/loop.c
@@ -592,7 +592,6 @@ execcase(Estate state, int do_exec)
     word = ecgetstr(state, EC_DUP, NULL);
     singsub(&word);
     untokenize(word);
-    lastval = 0;
 
     cmdpush(CS_CASE);
     while (state->pc < end) {
diff --git a/Test/A01grammar.ztst b/Test/A01grammar.ztst
index 0b1085c..0e77f3e 100644
--- a/Test/A01grammar.ztst
+++ b/Test/A01grammar.ztst
@@ -757,6 +757,14 @@
 >}
 >Stuff here
 
+  (exit 37)
+  case $? in
+    (37) echo $?
+    ;;
+  esac
+0:case retains exit status for execution of cases
+>37
+
   x=1
   x=2 | echo $x
   echo $x

Re: 'case' zeroes "$?"

[Martijn Dekker]

Op 10-10-16 om 10:55 schreef Peter Stephenson:
> On Sun, 9 Oct 2016 23:01:35 +0200
> Martijn Dekker <martijn@inlv.org> wrote:
>> > Unlike on other shells, 'case' on zsh zeroes "$?" before executing a
>> > command within 'case', making it more inconvenient to test exit status.
>> > 
>> > Example:
>> > 
>> > (exit 37) || case $? in 37) echo "$?";; esac
> This looks straightforward.

Perhaps not quite. The patch has introduced a new bug: instead of
prematurely resetting the exit status, it's now not reset at all.

Test script:

false
case stuff in (nomatch) foo ;; esac
echo $?

Expected output: 0
Actual output: 1

Reference:
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_04_05
"The exit status of case shall be zero if no patterns are matched.
Otherwise, the exit status shall be the exit status of the last command
executed in the compound-list."

So we need a flag to remember if any patterns are matched. Let me try my
hand at a patch for this:

diff --git a/Src/loop.c b/Src/loop.c
index 94b61b7..0b9ab15 100644
--- a/Src/loop.c
+++ b/Src/loop.c
@@ -584,7 +584,7 @@ execcase(Estate state, int do_exec)
     Wordcode end, next;
     wordcode code = state->pc[-1];
     char *word, *pat;
-    int npat, save, nalts, ialt, patok;
+    int npat, save, nalts, ialt, patok, anypatok;
     Patprog *spprog, pprog;

     end = state->pc + WC_CASE_SKIP(code);
@@ -592,6 +592,7 @@ execcase(Estate state, int do_exec)
     word = ecgetstr(state, EC_DUP, NULL);
     singsub(&word);
     untokenize(word);
+    anypatok = 0;

     cmdpush(CS_CASE);
     while (state->pc < end) {
@@ -648,7 +649,7 @@ execcase(Estate state, int do_exec)
 		    *spprog = pprog;
 	    }
 	    if (pprog && pattry(pprog, word))
-		patok = 1;
+		patok = anypatok = 1;
 	    state->pc += 2;
 	    nalts--;
 	}
@@ -679,6 +680,9 @@ execcase(Estate state, int do_exec)

     state->pc = end;

+    if (!anypatok)
+	lastval = 0;
+
     return lastval;
 }

diff --git a/Test/A01grammar.ztst b/Test/A01grammar.ztst
index 0e77f3e..e4b6870 100644
--- a/Test/A01grammar.ztst
+++ b/Test/A01grammar.ztst
@@ -765,6 +765,23 @@
 0:case retains exit status for execution of cases
 >37

+  false
+  case stuff in
+    (nomatch) foo
+    ;;
+  esac
+  echo $?
+0:case sets exit status to zero if no patterns are matched
+>0
+
+  case match in
+    (match) true; false; (exit 37)
+    ;;
+  esac
+  echo $?
+0:case keeps exit status of last command executed in compound-list
+>37
+
   x=1
   x=2 | echo $x
   echo $x