[VAR] Fix loss of variables when hash collides

Brian Koropoff reported that the new var patches broke the following
script:

#!/bin/dash
GDM_LANG="bar"
OPTION="foo"
unset GDM_LANG
# OPTION has mysteriously become unset
echo "$OPTION"

He correctly diagnosed this as a result of removing all variables
in the hash chain preceding the one that should be removed in
setvareq.

He also provided a patch to fix this.

This patch is based on his but without keeping the original vpp.
As a result, we now store new variables at the end of the hash
chain instead of the beginning.

To make this work, setvareq/setvar now returns the vp pointer
modified.  In case they're used to unset a variable the pointer
returned is undefined.  This is because mklocal needs it and
used to get it by assuming that the new variable always appear
at the beginning of the chain.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 22 insertions, 14 deletions

diff --git a/ChangeLog b/ChangeLog
index e45405c..48436b2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-07-06  Herbert Xu <herbert@gondor.apana.org.au>
+
+	* Fix loss of variables when hash collides.
+
 2010-06-28  Gerrit Pape <pape@smarden.org>
 
 	* Don't clear eflag in evalbackcmd.
diff --git a/src/var.c b/src/var.c
index f456fbd..3efc943 100644
--- a/src/var.c
+++ b/src/var.c
@@ -180,13 +180,13 @@ initvar(void)
  * flags of the variable.  If val is NULL, the variable is unset.
  */
 
-void
-setvar(const char *name, const char *val, int flags)
+struct var *setvar(const char *name, const char *val, int flags)
 {
 	char *p, *q;
 	size_t namelen;
 	char *nameeq;
 	size_t vallen;
+	struct var *vp;
 
 	q = endofname(name);
 	p = strchrnul(q, '=');
@@ -206,8 +206,10 @@ setvar(const char *name, const char *val, int flags)
 		p = mempcpy(p, val, vallen);
 	}
 	*p = '\0';
-	setvareq(nameeq, flags | VNOSAVE);
+	vp = setvareq(nameeq, flags | VNOSAVE);
 	INTON;
+
+	return vp;
 }
 
 /*
@@ -235,14 +237,14 @@ intmax_t setvarint(const char *name, intmax_t val, int flags)
  * Called with interrupts off.
  */
 
-void
-setvareq(char *s, int flags)
+struct var *setvareq(char *s, int flags)
 {
 	struct var *vp, **vpp;
 
 	vpp = hashvar(s);
 	flags |= (VEXPORT & (((unsigned) (1 - aflag)) - 1));
-	vp = *findvar(vpp, s);
+	vpp = findvar(vpp, s);
+	vp = *vpp;
 	if (vp) {
 		if (vp->flags & VREADONLY) {
 			const char *n;
@@ -255,7 +257,7 @@ setvareq(char *s, int flags)
 		}
 
 		if (flags & VNOSET)
-			return;
+			goto out;
 
 		if (vp->func && (flags & VNOFUNC) == 0)
 			(*vp->func)(strchrnul(s, '=') + 1);
@@ -270,13 +272,13 @@ setvareq(char *s, int flags)
 out_free:
 			if ((flags & (VTEXTFIXED|VSTACK|VNOSAVE)) == VNOSAVE)
 				ckfree(s);
-			return;
+			goto out;
 		}
 
 		flags |= vp->flags & ~(VTEXTFIXED|VSTACK|VNOSAVE|VUNSET);
 	} else {
 		if (flags & VNOSET)
-			return;
+			goto out;
 		if ((flags & (VEXPORT|VREADONLY|VSTRFIXED|VUNSET)) == VUNSET)
 			goto out_free;
 		/* not found */
@@ -289,6 +291,9 @@ out_free:
 		s = savestr(s);
 	vp->text = s;
 	vp->flags = flags;
+
+out:
+	return vp;
 }
 
 
@@ -486,10 +491,9 @@ void mklocal(char *name)
 		eq = strchr(name, '=');
 		if (vp == NULL) {
 			if (eq)
-				setvareq(name, VSTRFIXED);
+				vp = setvareq(name, VSTRFIXED);
 			else
-				setvar(name, NULL, VSTRFIXED);
-			vp = *vpp;	/* the new variable */
+				vp = setvar(name, NULL, VSTRFIXED);
 			lvp->flags = VUNSET;
 		} else {
 			lvp->text = vp->text;
diff --git a/src/var.h b/src/var.h
index 7e7e505..7aa051f 100644
--- a/src/var.h
+++ b/src/var.h
@@ -128,9 +128,9 @@ extern const char defpathvar[];
 #define mpathset()	((vmpath.flags & VUNSET) == 0)
 
 void initvar(void);
-void setvar(const char *, const char *, int);
+struct var *setvar(const char *name, const char *val, int flags);
 intmax_t setvarint(const char *, intmax_t, int);
-void setvareq(char *, int);
+struct var *setvareq(char *s, int flags);
 struct strlist;
 void listsetvar(struct strlist *, int);
 char *lookupvar(const char *);