[英]Access violation casting IDispatch in XE2
We're using some old code (ComLib.pas created by Binh Ly) so we can use the enumeration interface on an (OleVariant) object: 我们正在使用一些旧代码(由Binh Ly创建的ComLib.pas),因此我们可以在(OleVariant)对象上使用枚举接口:
type
TDispNewEnum = dispinterface
['{97079E31-6957-11D2-9154-0000B4552A26}'] // dummy
property _NewEnum: IUnknown readonly dispid -4; // DISPID_NEWENUM
function _NewEnumFunc: IUnknown; dispid -4; // DISPID_NEWENUM
end;
procedure TEnumVariant.AttachUnknown (const Unk: IUnknown);
var
pDisp: IDispatch;
_NewEnumPropFailed: boolean;
Unknown: IUnknown;
begin
Detach;
Unknown := Unk;
{ extract IEnumVariant }
if (Unknown <> nil) then
begin
{ try IEnumVariant }
if not (Succeeded (Unknown.QueryInterface (IEnumVariant, FEnumVariant))) then
begin
FEnumVariant := nil; // safety!
{ test _NewEnum prop and _NewEnum func }
if (Succeeded (Unknown.QueryInterface (IDispatch, pDisp))) then
begin
_NewEnumPropFailed := False;
try
//property _NewEnum
Unknown:=TDispNewEnum(pDisp)._NewEnum; // <---- RAISES EXCEPTION -----
if not (Succeeded(Unknown.QueryInterface(IEnumVariant, FEnumVariant))) then
FEnumVariant := nil; // safety!
except
_NewEnumPropFailed := True;
end; { except }
This code is working on Delphi 2010 and 2007, but not with XE2. 此代码适用于Delphi 2010和2007,但不适用于XE2。 On the line marked above (with the comment "RAISES EXCEPTION"), we get an exception:
在上面标记的行上(注释“RAISES EXCEPTION”),我们得到一个例外:
Project x.exe raised exception class $C0000005 with message 'access violation at 0xbaadf00d: read of address 0xbaadf00d'.
Project x.exe引发了异常类$ C0000005,并显示消息'0xbaadf00d的访问冲突:读取地址0xbaadf00d'。
The object passed in does have the TDispNewEnum interface so no exception should be raised (as is the case with Delphi 2010 and 2007). 传入的对象确实具有TDispNewEnum接口,因此不应引发任何异常(与Delphi 2010和2007的情况一样)。
Suggestions? 建议? Thanks.
谢谢。
The 0xbaadf00d
memory address is a pseudo memory address, meaning "BAD FOOD" (look at the hexa chars). 0xbaadf00d
内存地址是伪内存地址,意思是“BAD FOOD”(查看hexa chars)。 This is used usually by code when you ask for invalid interfaces or calls. 当您要求无效的接口或调用时,通常由代码使用。
What if you change the line into: 如果将行更改为:
pDisp: TDispNewEnum;
...
if (Succeeded (Unknown.QueryInterface (IDispatch, pDisp))) then
begin
_NewEnumPropFailed := False;
try
//property _NewEnum
Unknown:= pDisp._NewEnum;
...
which makes better sense to me. 这对我来说更有意义。
I've noticed some undocumented changes in the XE2 interface binding. 我注意到 XE2接口绑定中有一些未记录的更改。 Perhaps the previous code with a forced typecast (
TDispNewEnum(pDisp)
) is not working any more because of that. 也许以前使用强制类型转换的代码(
TDispNewEnum(pDisp)
)因为这个原因而无法正常工作。
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