c++ - 将 TopoDS_Face 对象分配给其子对象编译时没有错误，但有 3 个 valgrind 错误

Question

我有一个名为 Test 的类，它继承了 TopoDS_Face 类。已经从 This question 得到了一些提示但是...

    // Test.h
    class Test : public TopoDS_Face
    {
      public:
         void operator = (const TopoDS_Face& base_)
         {
            TopoDS_Face::operator=(base_);
         }
    }

    // testmain.cpp 
    ...
    int main() {
      //extract faces from IGES face
      for (int i = 1; i <= nbs; i++) {
        TopoDS_Shape shape = myIgesReader.Shape(i);
        TopoDS_Face& face = static_cast<TopoDS_Face&>(TopoDS::Face(shape));
        Test *test;
        // tried each of these also and did not succeed
        // Test *test = dynamic_cast<Test*>(&face);
        // test = &face

        test->TopoDS_Face::operator=(face);
        ...
    }

}

main 中的代码从 IGES 文件中提取面，并将每个面对象分配给 main 中创建的测试对象。编译进行得很顺利，但 valgrind 提示以下错误:

==21718== Use of uninitialised value of size 8
==21718==    at 0x9B0946C: Handle_Standard_Transient::Assign(Standard_Transient const*) (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x408111: Handle_TopoDS_TShape::operator=(Handle_TopoDS_TShape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x409478: TopoDS_Shape::operator=(TopoDS_Shape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x4094CA: TopoDS_Face::operator=(TopoDS_Face const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x407273: main (in /home/ub/Projects/C++/test/test)
==21718== 
==21718== Use of uninitialised value of size 8
==21718==    at 0x9B09431: Handle_Standard_Transient::EndScope() (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x9B09475: Handle_Standard_Transient::Assign(Standard_Transient const*) (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x408111: Handle_TopoDS_TShape::operator=(Handle_TopoDS_TShape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x409478: TopoDS_Shape::operator=(TopoDS_Shape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x4094CA: TopoDS_Face::operator=(TopoDS_Face const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x407273: main (in /home/ub/Projects/C++/test/test)
==21718== 
==21718== Invalid read of size 4
==21718==    at 0x9B0943C: Handle_Standard_Transient::EndScope() (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x9B09475: Handle_Standard_Transient::Assign(Standard_Transient const*) (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x408111: Handle_TopoDS_TShape::operator=(Handle_TopoDS_TShape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x409478: TopoDS_Shape::operator=(TopoDS_Shape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x4094CA: TopoDS_Face::operator=(TopoDS_Face const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x407273: main (in /home/ub/Projects/C++/test/test)
==21718==  Address 0x75eb394801c38350 is not stack'd, malloc'd or (recently) free'd
==21718== 
==21718== 
==21718== Process terminating with default action of signal 11 (SIGSEGV)
==21718==  General Protection Fault
==21718==    at 0x9B0943C: Handle_Standard_Transient::EndScope() (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x9B09475: Handle_Standard_Transient::Assign(Standard_Transient const*) (in /usr/lib64/libTKernel.so.10.0.0)
==21718==    by 0x408111: Handle_TopoDS_TShape::operator=(Handle_TopoDS_TShape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x409478: TopoDS_Shape::operator=(TopoDS_Shape const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x4094CA: TopoDS_Face::operator=(TopoDS_Face const&) (in /home/ub/Projects/C++/test/test)
==21718==    by 0x407273: main (in /home/ub/Projects/C++/test/test)
==21718== 

我需要帮助来解决该程序。提前致谢。

Answer 1

如果您查看TopoDS_Shape层次结构定义，您会注意到:

• TopoDS_Shape 不是一个接口(interface)(没有虚拟方法或虚拟析构函数)。

• TopoDS_Face、TopoDS_Shell 等提供从 TopoDS_Shape 的“虚拟”继承，无需添加任何字段或方法。

• OCCT 不存储强类型 TopoDS_ shape 对象。 OCCT 集合(首先包括 TopoDS_Shape 的子形状!)按值存储 TopoDS_Shape，而不是引用。像 TopoDS::Face() 这样的方法基本上会使用内存别名来返回强类型对象，并根据 TopoDS_Shape::ShapeType() 方法返回的枚举进行运行时检查。

• 实际上，可共享引用以 TopoDS_Shape 类的 Handle(TopoDS_TShape) 属性的形式存储。 TopoDS_TShape是一个定义主要形状数据(几何图形)的真实类，它确实是具有真实子类的虚拟类。

• TopoDS_TShape 层次结构(具有 TopoDS_TShape、TopoDS_TShell 等子类)是内部且最终的 - 没有用于在应用程序级别扩展此层次结构的接口(interface)。我想说，在 C++11 中，这些类应该被标记为 Final。

根据此描述，应该清楚的是，更改 TopoDS_Shape/TopoDS_TShape 层次结构与 OCCT 设计(对于这些特定类)相矛盾，并且无法在应用程序级别可靠地完成。假设的替代方案是使用映射(如 NCollection_DataMap<TopoDS_Shape,TopTools_ShapeMapHasher,MyShapeProperties> )或通过文档结构(如使用 TDataStd_NamedData 和其他属性定义装配结构的 XCAF 文档)存储与形状相关的附加信息。