[geos-commits] [SCM] GEOS branch 3.8 updated. 93be2e1d5a143d757e6cf5fc7c29c7ef48919ccf

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- Log -----------------------------------------------------------------
commit 93be2e1d5a143d757e6cf5fc7c29c7ef48919ccf
Author: Daniel Baston <dbaston at gmail.com>
Date:   Wed Oct 23 21:07:23 2019 -0400

    Avoid access past end of vector
    
    In most configurations this access would be optimized out (as it is
    never used) but this is not always the case.
    
    Fixes #1002

diff --git a/NEWS b/NEWS
index 770c9b0..003c2f5 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,7 @@ Changes in 3.8.1
 
 - Bug fixes / improvements
   - Stack allocate line segments in OverlapUnion (Paul Ramsey)
+  - Avoid assertion failure with MSVC 2017 / 2019 (#1002, Dan Baston)
 
 
 Changes in 3.8.0
diff --git a/src/index/chain/MonotoneChainBuilder.cpp b/src/index/chain/MonotoneChainBuilder.cpp
index be5836a..242a923 100644
--- a/src/index/chain/MonotoneChainBuilder.cpp
+++ b/src/index/chain/MonotoneChainBuilder.cpp
@@ -96,29 +96,28 @@ MonotoneChainBuilder::findChainEnd(const CoordinateSequence& pts, std::size_t st
     // (which is the starting quadrant)
     int chainQuad = Quadrant::quadrant(pts[safeStart],
                                        pts[safeStart + 1]);
-    std::size_t last = start + 1;
 
-    const Coordinate* prev = &pts[last-1]; // avoid repeated coordinate access by index (virtual call)
-    const Coordinate* curr = &pts[last];
+    const Coordinate* prev; // avoid repeated coordinate access by index (virtual call)
+    const Coordinate* curr = &pts[start];
+
+    for(size_t last = start + 1; last < npts; last++) {
+        prev = curr;
+        curr = &pts[last];
 
-    while(last < npts) {
         // skip zero-length segments, but include them in the chain
         if(!prev->equals2D(*curr)) {
             // compute quadrant for next possible segment in chain
             int quad = Quadrant::quadrant(*prev, *curr);
             if(quad != chainQuad) {
-                break;
+                return last - 1;
             }
         }
-        ++last;
-        prev = curr;
-        curr = &pts[last];
     }
 #if GEOS_DEBUG
     std::cerr << "MonotoneChainBuilder::findChainEnd() returning" << std::endl;
 #endif
 
-    return last - 1;
+    return npts - 1;
 }
 
 } // namespace geos.index.chain

-----------------------------------------------------------------------

Summary of changes:
 NEWS                                     |  1 +
 src/index/chain/MonotoneChainBuilder.cpp | 17 ++++++++---------
 2 files changed, 9 insertions(+), 9 deletions(-)


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