0031601: BRepOffset_Tool - Segmentation Fault

View Issue Details [ Jump to Notes ]

[ Issue History ] [ Print ]

Project

Category

View Status

Date Submitted

Last Update

0031601

Community

[OCCT] OCCT:Modeling Algorithms

public

2020-06-07 17:50

Reporter

abdullah

Assigned To

msv

Priority

normal

Severity

crash

Status

new

Resolution

open

Platform

Linux

Debian 6.0

OS Version

64 bit

Product Version

[OCCT] 7.3.0

Target Version

Fixed in Version

Summary

0031601: BRepOffset_Tool - Segmentation Fault

Description

A patch as possible solution is provided.

This has been tested and reproduced against development branch 7.4.1, commit ae58f70718a089f84178d45a1bf9bee586d52d80

This bug is based on the FreeCAD bug:
https://tracker.freecadweb.org/view.php?id=2325 [^]

The segmentation fault happens in function BRepOffset_Tool::TryProject.

In the following code (starting in line 1815):

   TopoDS_Edge CurE = TopoDS::Edge(it.Value());
    Handle(Geom_Curve) C = BRep_Tool::Curve(CurE,L,f,l);
    if (C.IsNull()) {
      BRepLib::BuildCurve3d(CurE,BRep_Tool::Tolerance(CurE));
      C = BRep_Tool::Curve(CurE,L,f,l);
    }
    C = new Geom_TrimmedCurve(C,f,l);

The curve produced by the call to BRep_Tool::Curve(CurE,L,f,l) is null.

Consequently the curve inserted into the constructor of Geom_TrimmedCurve is null. This causes the segfault.

I do not know whether BuildCurve3d is faulty (it should necessarily provide a non-null curve or not). I only know that in this specific case, it produces a null curve.

A possible solution to avoid the segmentation fault (see patch below), is to test whether the curve produced by BuildCurve3d is null.

An alternative to returning Standard_False (as in the patch) is to raise an exception. As no other function of this class raises an exception. None of the other functions of this class returns an exception, this my unqualified reason for returning Standard_False instead. You know the code better than me and may prefer an exception instead.

Steps To Reproduce

This bug is based on the FreeCAD bug:
https://tracker.freecadweb.org/view.php?id=2325 [^]

It is not easy to provide a way to reproduce it without FreeCAD. I am running a setup using a locally build FreeCAD with a locally build development branch of OCCT:
https://forum.freecadweb.org/viewtopic.php?f=10&t=47017&start=10#p405952 [^]

I think that based on the analysis above, you will be interested in preventing the segfault.

Of course, if you want to provide other code and would like me to test a possible patch or else, just contact me. I am ready to help.

Additional information
and documentation updates

This is a patch that prevents the segmentation fault.

diff --git a/src/BRepOffset/BRepOffset_Tool.cxx b/src/BRepOffset/BRepOffset_Tool.cxx
index af3ac106e1..b7c0d2310c 100644
--- a/src/BRepOffset/BRepOffset_Tool.cxx
+++ b/src/BRepOffset/BRepOffset_Tool.cxx
@@ -1820,0 +1821,3 @@ Standard_Boolean BRepOffset_Tool::TryProject
+ if (C.IsNull())
+ return Standard_False;
+

Issue History
Date Modified	Username	Field	Change
2020-06-07 17:50	abdullah	New Issue
2020-06-07 17:50	abdullah	Assigned To	=> msv

Relationships

Notes
There are no notes attached to this issue.