commit 8b20179c657b4266dff115486ca68c6a50324071
author Bram Moolenaar <Bram@vim.org> Fri Mar 25 15:01:10 2016 +0100
committer Bram Moolenaar <Bram@vim.org> Fri Mar 25 15:01:10 2016 +0100
tree df53aba36a9b71647886c07e04ba6b519005deb0
parent 4c90861e9f864eab94f043c432acff508396ed62

patch 7.4.1647
Problem:    Using freed memory after setqflist() and ":caddbuffer".  (Dominique)
Solution:   Set qf_ptr when adding the first item to the quickfix list.

src/quickfix.c

diff --git a/src/quickfix.c b/src/quickfix.c
index a2506e1..c2ff55a 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -1027,6 +1027,8 @@
 				/* first element in the list */
     {
 	qi->qf_lists[qi->qf_curlist].qf_start = qfp;
+	qi->qf_lists[qi->qf_curlist].qf_ptr = qfp;
+	qi->qf_lists[qi->qf_curlist].qf_index = 0;
 	qfp->qf_prev = qfp;	/* first element points to itself */
     }
     else
@@ -4113,7 +4115,8 @@
     else
 	qi->qf_lists[qi->qf_curlist].qf_nonevalid = FALSE;
     qi->qf_lists[qi->qf_curlist].qf_ptr = qi->qf_lists[qi->qf_curlist].qf_start;
-    qi->qf_lists[qi->qf_curlist].qf_index = 1;
+    if (qi->qf_lists[qi->qf_curlist].qf_count > 0)
+	qi->qf_lists[qi->qf_curlist].qf_index = 1;
 
 #ifdef FEAT_WINDOWS
     qf_update_buffer(qi);

src/testdir/test_quickfix.vim

diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 667ece4..e56c8a2 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -679,3 +679,11 @@
   call XquickfixChangedByAutocmd('c')
   call XquickfixChangedByAutocmd('l')
 endfunction
+
+func Test_caddbuffer_to_empty()
+  helpgr quickfix
+  call setqflist([], 'r')
+  cad
+  call assert_fails('cn', 'E553:')
+  quit!
+endfunc

src/version.c

diff --git a/src/version.c b/src/version.c
index 4ab8eed..95e2cba 100644
--- a/src/version.c
+++ b/src/version.c
@@ -749,6 +749,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1647,
+/**/
     1646,
 /**/
     1645,