From c6e56acc75db17a38a587cfe7ae3efddfba625ee Mon Sep 17 00:00:00 2001
From: Julian Seward <jseward@acm.org>
Date: Sat, 6 Aug 2016 07:15:30 +0000
Subject: [PATCH] Fix invalid code caught by Ubsan, in which we compute the
 address of "cgs->events[-1]", even though it isn't dereferenced.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15930
---
 cachegrind/cg_main.c | 20 ++++++++++----------
 callgrind/main.c     | 20 ++++++++++----------
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/cachegrind/cg_main.c b/cachegrind/cg_main.c
index de0c2a98a7..8a21bf2f8d 100644
--- a/cachegrind/cg_main.c
+++ b/cachegrind/cg_main.c
@@ -914,7 +914,6 @@ void addEvent_Dr ( CgState* cgs, InstrInfo* inode, Int datasize, IRAtom* ea )
 static
 void addEvent_Dw ( CgState* cgs, InstrInfo* inode, Int datasize, IRAtom* ea )
 {
-   Event* lastEvt;
    Event* evt;
 
    tl_assert(isIRAtom(ea));
@@ -924,15 +923,16 @@ void addEvent_Dw ( CgState* cgs, InstrInfo* inode, Int datasize, IRAtom* ea )
       return;
 
    /* Is it possible to merge this write with the preceding read? */
-   lastEvt = &cgs->events[cgs->events_used-1];
-   if (cgs->events_used > 0
-       && lastEvt->tag       == Ev_Dr
-       && lastEvt->Ev.Dr.szB == datasize
-       && lastEvt->inode     == inode
-       && eqIRAtom(lastEvt->Ev.Dr.ea, ea))
-   {
-      lastEvt->tag   = Ev_Dm;
-      return;
+   if (cgs->events_used > 0) {
+      Event* lastEvt = &cgs->events[cgs->events_used-1];
+      if (   lastEvt->tag       == Ev_Dr
+          && lastEvt->Ev.Dr.szB == datasize
+          && lastEvt->inode     == inode
+          && eqIRAtom(lastEvt->Ev.Dr.ea, ea))
+      {
+         lastEvt->tag   = Ev_Dm;
+         return;
+      }
    }
 
    /* No.  Add as normal. */
diff --git a/callgrind/main.c b/callgrind/main.c
index b62e835da3..69b0ddba29 100644
--- a/callgrind/main.c
+++ b/callgrind/main.c
@@ -637,7 +637,6 @@ void addEvent_Dr ( ClgState* clgs, InstrInfo* inode, Int datasize, IRAtom* ea )
 static
 void addEvent_Dw ( ClgState* clgs, InstrInfo* inode, Int datasize, IRAtom* ea )
 {
-   Event* lastEvt;
    Event* evt;
    tl_assert(isIRAtom(ea));
    tl_assert(datasize >= 1);
@@ -645,15 +644,16 @@ void addEvent_Dw ( ClgState* clgs, InstrInfo* inode, Int datasize, IRAtom* ea )
    tl_assert(datasize <= CLG_(min_line_size));
 
    /* Is it possible to merge this write with the preceding read? */
-   lastEvt = &clgs->events[clgs->events_used-1];
-   if (clgs->events_used > 0
-       && lastEvt->tag       == Ev_Dr
-       && lastEvt->Ev.Dr.szB == datasize
-       && lastEvt->inode     == inode
-       && eqIRAtom(lastEvt->Ev.Dr.ea, ea))
-   {
-      lastEvt->tag   = Ev_Dm;
-      return;
+   if (clgs->events_used > 0) {
+      Event* lastEvt = &clgs->events[clgs->events_used-1];
+      if (   lastEvt->tag       == Ev_Dr
+          && lastEvt->Ev.Dr.szB == datasize
+          && lastEvt->inode     == inode
+          && eqIRAtom(lastEvt->Ev.Dr.ea, ea))
+      {
+         lastEvt->tag   = Ev_Dm;
+         return;
+      }
    }
 
    /* No.  Add as normal. */
-- 
2.47.2