Make sure we don't introduce a circularity into the variable set linked

list.  Fixes Savannah bug #15757.

4 files changed, 53 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index e86bc3e..07d1e52 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2006-02-17  Paul D. Smith  <psmith@gnu.org>
+
+	* variable.c (merge_variable_set_lists): Don't try to merge the
+	global_setlist.  Not only is this useless, but it can lead to
+	circularities in the linked list, if global_setlist->next in one
+	list gets set to point to another list which also ends in
+	global_setlist.
+	Fixes Savannah bug #15757.
+
 2006-02-15  Paul D. Smith  <psmith@gnu.org>
 
 	Fix for Savannah bug #106.
diff --git a/tests/ChangeLog b/tests/ChangeLog
index c1342cb..57dec0d 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,9 @@
+2006-02-17  Paul D. Smith  <psmith@gnu.org>
+
+	* scripts/features/targetvars: Test a complex construction which
+	guarantees that we have to merge variable lists of different
+	sizes.  Tests for Savannah bug #15757.
+
 2006-02-15  Paul D. Smith  <psmith@gnu.org>
 
 	* scripts/functions/error: Make sure filename/lineno information
diff --git a/tests/scripts/features/targetvars b/tests/scripts/features/targetvars
index 3989340..c22ce13 100644
--- a/tests/scripts/features/targetvars
+++ b/tests/scripts/features/targetvars
@@ -267,4 +267,29 @@ close(MAKEFILE);
 $answer = "no build information\n";
 &compare_output($answer, &get_logfile(1));
 
+# TEST #17
+
+# Test a merge of set_lists for files, where one list is much longer
+# than the other.  See Savannah bug #15757.
+
+mkdir('t1');
+touch('t1/rules.mk');
+
+run_make_test('
+VPATH = t1
+include rules.mk
+.PHONY: all
+all: foo.x
+foo.x : rules.mk ; @echo MYVAR=$(MYVAR) FOOVAR=$(FOOVAR) ALLVAR=$(ALLVAR)
+all: ALLVAR = xxx
+foo.x: FOOVAR = bar
+rules.mk : MYVAR = foo
+.INTERMEDIATE: foo.x rules.mk
+',
+              '-I t1',
+              'MYVAR= FOOVAR=bar ALLVAR=xxx');
+
+rmfiles('t1/rules.mk');
+rmdir('t1');
+
 1;
diff --git a/variable.c b/variable.c
index 0ea71cd..39f0ada 100644
--- a/variable.c
+++ b/variable.c
@@ -665,21 +665,27 @@ void
 merge_variable_set_lists (struct variable_set_list **setlist0,
                           struct variable_set_list *setlist1)
 {
-  register struct variable_set_list *list0 = *setlist0;
+  struct variable_set_list *to = *setlist0;
   struct variable_set_list *last0 = 0;
 
-  while (setlist1 != 0 && list0 != 0)
+  /* If there's nothing to merge, stop now.  */
+  if (!setlist1)
+    return;
+
+  /* This loop relies on the fact that all setlists terminate with the global
+     setlist (before NULL).  If that's not true, arguably we SHOULD die.  */
+  while (setlist1 != &global_setlist && to != &global_setlist)
     {
-      struct variable_set_list *next = setlist1;
+      struct variable_set_list *from = setlist1;
       setlist1 = setlist1->next;
 
-      merge_variable_sets (list0->set, next->set);
+      merge_variable_sets (to->set, from->set);
 
-      last0 = list0;
-      list0 = list0->next;
+      last0 = to;
+      to = to->next;
     }
 
-  if (setlist1 != 0)
+  if (setlist1 != &global_setlist)
     {
       if (last0 == 0)
 	*setlist0 = setlist1;