[mapserver-dev] Offset x -99 AGG crash

[Torsten Weber]

Hi all,

I don't know, if this is the correct way to report this.

Mapserver runs on a segfault in the following very special case using the agg 
renderer (GD Renderer works). 
Possibly this stands in context with #2732 and #2659 (discussed 
fixes/modifications are applied):

We have a line layer which has some lines with only two points at the same 
location. (not really meaningful, I know) Normal rendering works, rendering 
with "OFFSET x -99" crashes. 

I had a look at the source and found a simple solution. There is a Query at 
maputils.c at line 1493 (from the 5.2 final source) to ignore duplicate 
points. In this special case it reduces the line to one point and mapserver 
crashes.

I've changed the line from 
  if (dx==0) {
    if (dy==0) {
      continue;
    } 
  ....
to 
  if (dx==0) {
    if (dy==0 && first==0) {
      continue;
    } 
  ...
so only duplicated points in the middle of a line are ignored and the chrash 
disappears. Tested with shp2img and php_mapscript.

Our Environment:
SuSE Linux 10.3 with kernel 2.6.22.18 64bit
Intel Quadcore 
4GB RAM
MapServer version 5.2.0 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP 
OUTPUT=SVG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=ICONV 
SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER 
SUPPORTS=WFS_CLIENT SUPPORTS=WCS_SERVER SUPPORTS=SOS_SERVER SUPPORTS=THREADS 
INPUT=TIFF INPUT=EPPL7 INPUT=ORACLESPATIAL INPUT=OGR INPUT=GDAL 
INPUT=SHAPEFILE

Regards,

Torsten Weber
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