From 692decba26f4cb93f9ce2d1aafd658f104d9bdc4 Mon Sep 17 00:00:00 2001
From: dpasukhi <dpasukhi@opencascade.com>
Date: Sat, 17 Oct 2020 16:21:51 +0300
Subject: [PATCH] 0031825: Data Exchange, STEP - NULL dereference while
 re-exporting model with empty Datum description

Fix adding name and description of the datum
---
 src/STEPCAFControl/STEPCAFControl_Reader.cxx |  4 +-
 src/STEPCAFControl/STEPCAFControl_Writer.cxx |  6 ++-
 tests/bugs/step/bug31825                     | 40 ++++++++++++++++++++
 3 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 tests/bugs/step/bug31825

diff --git a/src/STEPCAFControl/STEPCAFControl_Reader.cxx b/src/STEPCAFControl/STEPCAFControl_Reader.cxx
index 146fed35c8..029d9f4d0d 100644
--- a/src/STEPCAFControl/STEPCAFControl_Reader.cxx
+++ b/src/STEPCAFControl/STEPCAFControl_Reader.cxx
@@ -2527,7 +2527,7 @@ Standard_Boolean STEPCAFControl_Reader::setDatumToXCAF(const Handle(StepDimTol_D
 
     // Create datum target object
     if (isValidDT) {
-      TDF_Label aDatL = aDGTTool->AddDatum();
+      TDF_Label aDatL = aDGTTool->AddDatum(theDat->Name(), theDat->Description(), theDat->Identification());
       myGDTMap.Bind(aDT, aDatL);
       aDGTTool->Lock(aDatL);
       aDat = XCAFDoc_Datum::Set(aDatL);
@@ -2549,7 +2549,7 @@ Standard_Boolean STEPCAFControl_Reader::setDatumToXCAF(const Handle(StepDimTol_D
 
   if (aShapeLabels.Length() > 0 || !isExistDatumTarget) {
     // Create object for datum
-    TDF_Label aDatL = aDGTTool->AddDatum();
+    TDF_Label aDatL = aDGTTool->AddDatum(theDat->Name(), theDat->Description(), theDat->Identification());
     myGDTMap.Bind(theDat, aDatL);
     // bind datum label with all reference datum_feature entities
     for (Standard_Integer i = 1; i <= aSAs.Length(); i++) {
diff --git a/src/STEPCAFControl/STEPCAFControl_Writer.cxx b/src/STEPCAFControl/STEPCAFControl_Writer.cxx
index a988be2806..30646bc99b 100644
--- a/src/STEPCAFControl/STEPCAFControl_Writer.cxx
+++ b/src/STEPCAFControl/STEPCAFControl_Writer.cxx
@@ -3466,8 +3466,12 @@ Standard_Boolean STEPCAFControl_Writer::WriteDGTs (const Handle(XSControl_WorkSe
     Handle(XCAFDoc_Datum) DatumAttr;
     if(!DatumL.FindAttribute(XCAFDoc_Datum::GetID(),DatumAttr)) continue;
     Handle(TCollection_HAsciiString) aName = DatumAttr->GetName();
-    Handle(TCollection_HAsciiString) aDescription = DatumAttr->GetDescription();
     Handle(TCollection_HAsciiString) anIdentification = DatumAttr->GetIdentification();
+    Handle(TCollection_HAsciiString) aDescription = DatumAttr->GetDescription();
+    if (aDescription.IsNull())
+    {
+      aDescription = new TCollection_HAsciiString();
+    }
     Handle(StepDimTol_DatumFeature) DF = new StepDimTol_DatumFeature;
     Handle(StepDimTol_Datum) aDatum = new StepDimTol_Datum;
     DF->Init(aName, new TCollection_HAsciiString, PDS, StepData_LTrue);
diff --git a/tests/bugs/step/bug31825 b/tests/bugs/step/bug31825
new file mode 100644
index 0000000000..b05c96255c
--- /dev/null
+++ b/tests/bugs/step/bug31825
@@ -0,0 +1,40 @@
+puts "================"
+puts "0031825: Data Exchange, STEP - NULL dereference while re-exporting model with empty Datum description"
+puts "================"
+puts ""
+
+pload OCAF
+param write.step.schema AP242DIS
+catch { Close D_First }
+catch { Close D_Sec }
+
+# Read file
+set Path ${imagedir}/${casename}.stp
+ReadStep D_First [locate_data_file bug26689_nist_ctc_04_asme1_ap242.stp]
+set baseDGTDump [XDumpNbDGTs D_First f]
+
+WriteStep D_First $Path
+ReadStep D_Sec $Path
+file delete $Path
+set newDGTDump [XDumpNbDGTs D_Sec f]
+XGetOneShape res D_Sec
+
+# Checking
+checkshape res
+checknbshapes res -face 518 -wire 623 -compound 1
+
+set isOK 1
+set nb_ref [llength $newDGTDump]
+for { set i 0 } { $i < $nb_ref } { incr i } {
+  set refstr [lindex $baseDGTDump $i]
+  set curstr [lindex $newDGTDump $i]
+  if {[string equal $refstr $curstr] == 0} {
+    set isOK 0
+  }
+}
+if {$isOK == 0} {
+  puts "Error: wrong export DGT and PMI"
+}
+
+# set default parameter
+param write.step.schema AP214IS