[osg-submissions] Handling Empty/NULL strings in ShapeAttributeList

[John Vidar Larring]

Hi All,

Short version:
--------------

Problem: Empty string value in an osgSim::ShapeAttributeList causes 
SIGSEV when loading a .osg file.

Solution: Changing line 47 in src/osgSim/ShapeAttribute.cpp from:
-    std::string str(value);
+    std::string str((value ? value : ""));

Attached file is a modification of src/osgSim/ShapeAttribute.cpp in svn 
revision 8426.

Long version (including context):
---------------------------------

osgGIS now allows the user to keep meta-data when converting ESRI Shape 
files to OSG graph:

osggis: world.shp -> world.osg:
[...snip...]
                 Geode {
                   UserData {
                     osgSim::ShapeAttributeList {
                       string "cntry_name" "Antarctica"
                       int    "colormap" 7
                       string "curr_code" "NCIC"
                       string "curr_type" ""
                       string "fips_cntry" "AY"
                       string "gmi_cntry" "ATA"
                       string "iso_2digit" "AQ"
                       string "iso_3digit" "ATA"
                       string "landlocked" "N"
                       string "long_name" "Antarctica"
                       int    "pop_cntry" -99999
                       string "sovereign" "Antarctica"
                       double "sqkm" 1.23031e+07
                       double "sqmi" 4.75021e+06
                     }
                   }
[...snip...]

...which is parallell to what 'osgconv world.shp world.osg' produces:
[...snip...]
   Geometry {
     DataVariance STATIC
     UserData {
       osgSim::ShapeAttributeList {
         string "FIPS_CNTRY" "AY"
         string "GMI_CNTRY" "ATA"
         string "ISO_2DIGIT" "AQ"
         string "ISO_3DIGIT" "ATA"
         string "CNTRY_NAME" "Antarctica 
 
 
                                                                       "
         string "LONG_NAME" "Antarctica                              "
         string "SOVEREIGN" "Antarctica                              "
         int    "POP_CNTRY" -99999
         string "CURR_TYPE" "                "
         string "CURR_CODE" "NCIC"
         string "LANDLOCKED" "N"
         int    "SQKM" 12303052
         int    "SQMI" 4750207
         int    "COLORMAP" 7
       }
     }
[...snip...]

The difference is that osgconv (a.k.a. shp plugin) adds whitespace to 
string "curr_type" while osggis does not. However, the output from 
osggis is cleaner and should IMHO be acceptable.

However, osgDB::Input in ShapeAttributeList_readLocalData converts the 
empty string to a NULL pointer:

bool ShapeAttributeList_readLocalData(osg::Object &obj, osgDB::Input &fr)
{
     bool iteratorAdvanced = false;
     ShapeAttributeList &sal = static_cast<ShapeAttributeList &>(obj);

     int entry = fr[0].getNoNestedBrackets();

     while (!fr.eof() && fr[0].getNoNestedBrackets()>=entry)
     {
         if (fr.matchSequence("string %s %s"))
         {
             sal.push_back(osgSim::ShapeAttribute(fr[1].getStr(), 
fr[2].getStr()));  <<== fr[2].getStr() returns NULL for 'string 
"curr_type" ""'
             fr += 3;
             iteratorAdvanced = true;
         }
[...snip...]

This results in a SIGSEV in ShapeAttribute::ShapeAttribute(const char * 
name, const char * value) with the following stack trace:

#0  0x00000030a032e25d in raise () from /lib64/tls/libc.so.6
#1  0x00000030a032fa5e in abort () from /lib64/tls/libc.so.6
#2  0x00000030a28b1148 in __gnu_cxx::__verbose_terminate_handler () from 
/usr/lib64/libstdc++.so.6
#3  0x00000030a28af176 in __cxa_call_unexpected () from 
/usr/lib64/libstdc++.so.6
#4  0x00000030a28af1a3 in std::terminate () from /usr/lib64/libstdc++.so.6
#5  0x00000030a28af2a3 in __cxa_throw () from /usr/lib64/libstdc++.so.6
#6  0x00000030a2851bf0 in std::__throw_logic_error () from 
/usr/lib64/libstdc++.so.6
#7  0x00000030a2892706 in std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >::basic_string$base () 
from /usr/lib64/libstdc++.so.6
#8  0x00000030a28927b3 in std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >::basic_string () from 
/usr/lib64/libstdc++.so.6
#9  0x0000002a96c9c2d7 in osgSim::ShapeAttribute::ShapeAttribute () at 
/usr/lib/gcc/x86_64-redhat-linux/3.4.6/../../../../include/c++/3.4.6/bits/locale_facets.tcc:2443
#10 0x0000002a98083d16 in ShapeAttributeList_readLocalData 
(obj=@0x5601c0, fr=@0x7fbfffdde0) at 
/home/john/external.el4/OpenSceneGraph/trunk/src/osgPlugins/osgSim/IO_ShapeAttribute.cpp:38
#11 0x0000002a95cab5b0 in osgDB::Registry::readObject (this=0x51ac90, 
dowMap=@0x51acc8, fr=@0x7fbfffdde0) at 
/home/john/external.el4/OpenSceneGraph/trunk/src/osgDB/Registry.cpp:1003
#12 0x0000002a95cab78a in osgDB::Registry::readObject (this=0x51ac90, 
fr=@0x7fbfffdde0) at 
/home/john/external.el4/OpenSceneGraph/trunk/src/osgDB/Registry.cpp:1036

The attached file fixes the problem by testing for NULL pointer value in 
  ShapeAttribute::ShapeAttribute.

Best regards,
John

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