Re: environment variables

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

On Tue, 31 Aug 2010 17:54:25 +0200
Joke de Buhr <joke@seiken.de> wrote:
> ## 4: HELLO not exported to shell function, different from 2 and 3
> $ call() { env | grep '^HELLO' }
> $ HELLO=world
> $ HELLO=$HELLO call
>     HELLO=      ## <-- empty

(Moved to zsh-workers immediately, this time.)

That's a bug.  When HELLO needs to be restored explicitly because the
code where it's set to something else is running in the main shell, we
remove the parameter from the table to be restored later.  The
assignment than can't see the value it's temporarily modifying.  You
don't need to search the environment for this; zsh consistently screws
up the parameter within the shell, too.

I think we can just copy the parameter instead of removing it, so long
as we copy it properly.

valgrind says this doesn't cause any leaks.

Index: Src/exec.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/exec.c,v
retrieving revision 1.182
diff -p -u -r1.182 exec.c
--- Src/exec.c	22 Aug 2010 20:08:57 -0000	1.182
+++ Src/exec.c	31 Aug 2010 19:11:41 -0000
@@ -3313,13 +3313,17 @@ save_params(Estate state, Wordcode pc, L
     while (wc_code(ac = *pc) == WC_ASSIGN) {
 	s = ecrawstr(state->prog, pc + 1, NULL);
 	if ((pm = (Param) paramtab->getnode(paramtab, s))) {
+	    Param tpm;
 	    if (pm->env)
 		delenv(pm);
 	    if (!(pm->node.flags & PM_SPECIAL)) {
-		paramtab->removenode(paramtab, s);
+		tpm = (Param) zshcalloc(sizeof *tpm);
+		tpm->node.nam = ztrdup(pm->node.nam);
+		copyparam(tpm, pm, 0);
+		pm = tpm;
 	    } else if (!(pm->node.flags & PM_READONLY) &&
 		       (unset(RESTRICTED) || !(pm->node.flags & PM_RESTRICTED))) {
-		Param tpm = (Param) hcalloc(sizeof *tpm);
+		tpm = (Param) hcalloc(sizeof *tpm);
 		tpm->node.nam = pm->node.nam;
 		copyparam(tpm, pm, 1);
 		pm = tpm;
@@ -3383,8 +3387,9 @@ restore_params(LinkList restorelist, Lin
 		    break;
 		}
 		pm = tpm;
-	    } else
+	    } else {
 		paramtab->addnode(paramtab, pm->node.nam, pm);
+	    }
 	    if ((pm->node.flags & PM_EXPORTED) && ((s = getsparam(pm->node.nam))))
 		addenv(pm, s);
 	}
Index: Src/params.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/params.c,v
retrieving revision 1.161
diff -p -u -r1.161 params.c
--- Src/params.c	3 Jun 2010 13:38:17 -0000	1.161
+++ Src/params.c	31 Aug 2010 19:11:41 -0000
@@ -927,11 +927,17 @@ createspecialhash(char *name, GetNodeFun
 }
 
 
-/* Copy a parameter */
+/*
+ * Copy a parameter
+ *
+ * If fakecopy is set, we are just saving the details of a special
+ * parameter.  Otherwise, the result will be used as a real parameter
+ * and we need to do more work.
+ */
 
 /**/
 void
-copyparam(Param tpm, Param pm, int toplevel)
+copyparam(Param tpm, Param pm, int fakecopy)
 {
     /*
      * Note that tpm, into which we're copying, may not be in permanent
@@ -942,7 +948,8 @@ copyparam(Param tpm, Param pm, int tople
     tpm->node.flags = pm->node.flags;
     tpm->base = pm->base;
     tpm->width = pm->width;
-    if (!toplevel)
+    tpm->level = pm->level;
+    if (!fakecopy)
 	tpm->node.flags &= ~PM_SPECIAL;
     switch (PM_TYPE(pm->node.flags)) {
     case PM_SCALAR:
@@ -963,13 +970,15 @@ copyparam(Param tpm, Param pm, int tople
 	break;
     }
     /*
-     * If called from inside an associative array, that array is later going
-     * to be passed as a real parameter, so we need the gets and sets
-     * functions to be useful.  However, the saved associated array is
-     * not itself special, so we just use the standard ones.
-     * This is also why we switch off PM_SPECIAL.
+     * If the value is going to be passed as a real parameter (e.g. this is
+     * called from inside an associative array), we need the gets and sets
+     * functions to be useful.
+     *
+     * In this case we assume the the saved parameter is not itself special,
+     * so we just use the standard functions.  This is also why we switch off
+     * PM_SPECIAL.
      */
-    if (!toplevel)
+    if (!fakecopy)
 	assigngetset(tpm);
 }
 
Index: Test/A06assign.ztst
===================================================================
RCS file: /cvsroot/zsh/zsh/Test/A06assign.ztst,v
retrieving revision 1.5
diff -p -u -r1.5 A06assign.ztst
--- Test/A06assign.ztst	23 Sep 2006 06:55:29 -0000	1.5
+++ Test/A06assign.ztst	31 Aug 2010 19:11:41 -0000
@@ -277,3 +277,18 @@
 >
 >
 >
+
+  call() { print $HELLO; }
+  export HELLO=world
+  call
+  HELLO=universe call
+  call
+  HELLO=${HELLO}liness call
+  call
+  unset HELLO
+0:save and restore when using original value in temporary
+>world
+>universe
+>world
+>worldliness
+>world


-- 
Peter Stephenson <p.w.stephenson@ntlworld.com>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/