Visual C++ Exception-Handling Instrumentation

Listing 2 Exception-handling internal structures

/*  these types are known to compiler without declaration

// this structure is used to calculate
// an offset of a sub-type from the beginning
// of an object. I do not know the exact meaning
// of its members
struct _PMD
{
    int mdisp;
    int pdisp;
    int vdisp;
};

// information of a type that
// can be caught by a catch block
struct _s__CatchableType
{
    //type properties bit flags
    // 1 - type is a pointer
    // 2 - ????
    unsigned properties;
    // _TypeDescriptor is the same
    // as good old type_info. 
    _TypeDescriptor * pType;
    // used to calculate displacement of 
    // this pointer for the type from
    // the beginning of the object
    _PMD thisDisplacement;
    // size of the type
    int sizeOrOffset;
    // function used to copy the type around
    // if the type has copy ctor it will
    // be it. Otherwise 0
    void (*)() copyFunction; 
};

// a counted array of the types that can
// be caught by a catch block 
struct _s__CatchableTypeArray
{
    // count of the types
    int nCatchableTypes;
    // pointer to an array
    const _s__CatchableType
      (* arrayOfCatchableTypes)[];
};

// this structure holds the information about
// exception object being thrown
struct _s__ThrowInfo
{
    //object attributes bitmask
    // 1 - object is pointer to const object
    // 2 - object is pointer to volatile object
    unsigned attributes;
    // pointer to function to destroy
    // the exception object. Probably always
    // the destructor
    void * pmfnUnwind;
    // pointer to special exception
    // handling function
    // not relevant to this article
    void * pForwardCompat;
    // array of sub-types of the object
    // or other types to 
    // which it could be implicitly cast.
    // Used to find 
    // the matching catch block
    const _s__CatchableTypeArray *
      pCatchableTypeArray;
};


*/