41113 (tweaked): Save current line linkage to history ring.

When saving history state save whether the current history line
is linked into the ring and remove it, and restore as appropriate
later.  This avoids surprises where the history ring is freed
and incorrectly frees the current state in curline, which has
a different allocation strategy.

Original patch tweaked to make restoring more logical.

4 files changed, 35 insertions, 15 deletions

diff --git a/ChangeLog b/ChangeLog
index e608b167f..b5060864a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-05-18  Peter Stephenson  <p.stephenson@samsung.com>
+
+	* 41113 (tweaked): Src/hashtable,c, Src/hist.c, Src/zsh.h: Save
+	and restore state of linking of current history line into history
+	ring, to avoid an attempt to free the current history line.
+
 2017-05-12  Jun-ichi Takimoto <takimoto-j@kba.biglobe.ne.jp>
 
 	* 41090: Src/Zle/zle_refresh.c, Src/compat.c, Src/pattern.c,
diff --git a/Src/hashtable.c b/Src/hashtable.c
index ba5faad91..c34744cd8 100644
--- a/Src/hashtable.c
+++ b/Src/hashtable.c
@@ -1448,6 +1448,7 @@ freehistdata(Histent he, int unlink)
     if (!(he->node.flags & (HIST_DUP | HIST_TMPSTORE)))
 	removehashnode(histtab, he->node.nam);
 
+    DPUTS(he->node.nam == chline, "Attempt to free chline in history data");
     zsfree(he->node.nam);
     if (he->nwords)
 	zfree(he->words, he->nwords*2*sizeof(short));
diff --git a/Src/hist.c b/Src/hist.c
index 350688d2d..4c1039b67 100644
--- a/Src/hist.c
+++ b/Src/hist.c
@@ -87,6 +87,9 @@ mod_export zlong curhist;
 /**/
 struct histent curline;
 
+/***/
+int curline_linked;
+
 /* current line count of allocated history entries */
 
 /**/
@@ -261,6 +264,9 @@ hist_context_save(struct hist_stack *hs, int toplevel)
      */
     hs->cstack = cmdstack;
     hs->csp = cmdsp;
+    hs->curline_linked = curline_linked;
+
+    unlinkcurline();
 
     stophist = 0;
     chline = NULL;
@@ -300,6 +306,9 @@ hist_context_restore(const struct hist_stack *hs, int toplevel)
 	zfree(cmdstack, CMDSTACKSZ);
     cmdstack = hs->cstack;
     cmdsp = hs->csp;
+    unlinkcurline();
+    if (hs->curline_linked)
+	linkcurline();
 }
 
 /*
@@ -990,6 +999,7 @@ nohwe(void)
 
 /* these functions handle adding/removing curline to/from the hist_ring */
 
+/**/
 static void
 linkcurline(void)
 {
@@ -1002,11 +1012,15 @@ linkcurline(void)
 	hist_ring = &curline;
     }
     curline.histnum = ++curhist;
+    curline_linked = 1;
 }
 
+/**/
 static void
 unlinkcurline(void)
 {
+    if (!curline_linked)
+	return;
     curline.up->down = curline.down;
     curline.down->up = curline.up;
     if (hist_ring == &curline) {
@@ -1016,6 +1030,7 @@ unlinkcurline(void)
 	    hist_ring = curline.up;
     }
     curhist--;
+    curline_linked = 0;
 }
 
 /* initialize the history mechanism */
@@ -1035,6 +1050,7 @@ hbegin(int dohist)
 	stophist = (!interact || unset(SHINSTDIN)) ? 2 : 0;
     else
 	stophist = 0;
+    DPUTS(chline != NULL, "chline set at start of history");
     /*
      * pws: We used to test for "|| (inbufflags & INP_ALIAS)"
      * in this test, but at this point we don't have input
@@ -1292,11 +1308,10 @@ putoldhistentryontop(short keep_going)
 Histent
 prepnexthistent(void)
 {
-    Histent he; 
-    int curline_in_ring = hist_ring == &curline;
+    Histent he;
+    int relink_curline = curline_linked;
 
-    if (curline_in_ring)
-	unlinkcurline();
+    unlinkcurline();
     if (hist_ring && hist_ring->node.flags & HIST_TMPSTORE) {
 	curhist--;
 	freehistnode(&hist_ring->node);
@@ -1320,7 +1335,7 @@ prepnexthistent(void)
 	he = hist_ring;
     }
     he->histnum = ++curhist;
-    if (curline_in_ring)
+    if (relink_curline)
 	linkcurline();
     return he;
 }
@@ -1395,8 +1410,7 @@ hend(Eprog prog)
     queue_signals();
     if (histdone & HISTFLAG_SETTY)
 	settyinfo(&shttyinfo);
-    if (!(histactive & HA_NOINC))
-	unlinkcurline();
+    unlinkcurline();
     if (histactive & HA_NOINC) {
 	zfree(chline, hlinesz);
 	zfree(chwords, chwordlen*sizeof(short));
@@ -3624,7 +3638,7 @@ int
 pushhiststack(char *hf, zlong hs, zlong shs, int level)
 {
     struct histsave *h;
-    int curline_in_ring = (histactive & HA_ACTIVE) && hist_ring == &curline;
+    int relink_curline = curline_linked;
 
     if (histsave_stack_pos == histsave_stack_size) {
 	histsave_stack_size += 5;
@@ -3632,8 +3646,7 @@ pushhiststack(char *hf, zlong hs, zlong shs, int level)
 			    histsave_stack_size * sizeof (struct histsave));
     }
 
-    if (curline_in_ring)
-	unlinkcurline();
+    unlinkcurline();
 
     h = &histsave_stack[histsave_stack_pos++];
 
@@ -3668,7 +3681,7 @@ pushhiststack(char *hf, zlong hs, zlong shs, int level)
     savehistsiz = shs;
     inithist(); /* sets histtab */
 
-    if (curline_in_ring)
+    if (relink_curline)
 	linkcurline();
 
     return histsave_stack_pos;
@@ -3680,13 +3693,12 @@ int
 pophiststack(void)
 {
     struct histsave *h;
-    int curline_in_ring = (histactive & HA_ACTIVE) && hist_ring == &curline;
+    int relink_curline = curline_linked;
 
     if (histsave_stack_pos == 0)
 	return 0;
 
-    if (curline_in_ring)
-	unlinkcurline();
+    unlinkcurline();
 
     deletehashtable(histtab);
     zsfree(lasthist.text);
@@ -3709,7 +3721,7 @@ pophiststack(void)
     histsiz = h->histsiz;
     savehistsiz = h->savehistsiz;
 
-    if (curline_in_ring)
+    if (relink_curline)
 	linkcurline();
 
     return histsave_stack_pos + 1;
diff --git a/Src/zsh.h b/Src/zsh.h
index 22f73f806..405b27490 100644
--- a/Src/zsh.h
+++ b/Src/zsh.h
@@ -2931,6 +2931,7 @@ struct hist_stack {
     void (*addtoline) _((int));
     unsigned char *cstack;
     int csp;
+    int curline_linked;
 };
 
 /*