ptr in VC6 dll cause crash
// dll
#include <memory>
__declspec(dllexport) std::auto_ptr<int> get();
__declspec(dllexport) std::auto_ptr<int> get()
{
return std::auto_ptr<int>(new int());
}
// exe
#include <iostream>
#include <memory>
__declspec(dllimport) std::auto_ptr<int> get();
int main() {
{
std::auto_ptr<int> x = get();
}
std::cout << "donen";
getchar();
}
The following code run perfectly OK under VC9. However, under VC6, I will experience an immediate crash with the following message.
Debug Assertion Failed!
Program: C:Projectsuse_dynamic_linkDebuguse_dynamic_link.exe File: dbgheap.c Line: 1044
Expression: _CrtIsValidHeapPointer(pUserData)
Is it exporting auto_ptr under VC6 is not allowed?
It is a known problem that exporting STL collection classes through DLL.
Access Violation When Accessing an STL Object Through A Pointer or Reference In A Different DLL or EXE
However, I Google around and do not see anything mention for std::auto_ptr.
Any workaround?
一个DLL有自己的堆，所以你必须确保你是新的，并从同一个上下文中删除。
My first guess would be that the exe and dll projects in VC9 are set up for the CRT to be targeted as a shared dll, while one or both of the VC6 projects is targeting the static CRT (non-dll).
Alternatively, both the dll and exe are targeting different versions of a shared CRT dll (so they actually use 2 different CRTs).
In VC6, check the run-time library option in the Code Generation category of the C/C++ Project properties. Make sure both the exe and dll target the same DLL library option.
You're violating the ODR (one definition rule) and most likely the member functions are inlined -- since they are inlined with two different definitions of std::auto_ptr you get undefined behavior.
On top of that, as Eddy points out, when auto_ptr::~auto_ptr frees the held object, it will call operator delete in the EXE instead of in the DLL where operator new was called. This mismatch can also produce a crash.
In general it is very fragile to export implemented classes (interface classes consisting solely of pure virtual functions, and exporting a free factory function for construction) are OK and then you don't use __declspec(dllexport) on the class, only on the factory function.
下一篇: 在VC6 DLL中的ptr导致崩溃