Article ID: 102619
Article Last Modified on 7/5/2005
APPLIES TO
- Microsoft Visual C++ 1.0 Professional Edition
- Microsoft Visual C++ 1.5 Professional Edition
This article was previously published under Q102619
SYMPTOMS
After compiling an application with Microsoft C/C++ for MS-DOS, an attempt to link the application fails and Microsoft LINK generates the following message:
After compiling an application with Microsoft C/C++ 32-bit Edition, an attempt to link the application fails and Microsoft LINK generates the following messages:
CAUSE
Microsoft C/C++ compiler version 8.0 and 8.0c for MS-DOS and Windows always uses the __cdecl calling convention for functions declared as follows:
<classname>::operator const <type-specifier> *() const
However, if the compiler command line includes the /Gc compiler option switch, the function has the __pascal calling convention. Normally, every member function of a class uses the __pascal calling convention without regard to the presence of the /Gc compiler option switch.
For example, if you build an application with the Microsoft Foundation Class Library and refer to the function CString::operator const char *() const, an L2029 error occurs if you specify the /Gc compiler option switch. Because the Class Library was built without the /Gc option, the conversion function in the library has the __cdecl calling convention. If you build your application with the /Gc option switch, it attempts to call the conversion function with the __pascal calling convention.
A similar problem occurs in Microsoft C/C++ 32-bit Edition if you specify the /Gz compiler option switch. Normally, each class member function uses the thiscall calling convention without regard to the presence of the /Gz compiler option switch. However, if the compiler command line specifies the /Gz compiler option switch, the conversion function uses the __stdcall calling convention.
RESOLUTION
In Microsoft C/C++ version 8.0 for MS-DOS and Windows, modify the compiler command line to remove the /Gc compiler option switch. Doing so compiles the conversion function with the __cdecl calling convention. In Microsoft C/C++ version 8.0 (32-bit), modify the compiler command line to remove the /Gz compiler option switch. Doing so compiles the conversion function with the thiscall calling convention.
STATUS
Microsoft has confirmed this to be a bug in the products listed at the beginning of this article. This bug was corrected in Visual C++ version 2.0.
MORE INFORMATION
The code example below demonstrates this problem. Recall that because member functions use the __pascal or thiscall calling convention, compiling MAIN.CPP with the /Gc or /Gz switches specified or not should not make any difference. However, the example shows that a problem does occur.
The code below demonstrates the problem. Recall that member functions use the __pascal or thiscall calling convention, and therefore there should be no difference between using /Gc or /Gz with MAIN.CPP and not using /Gc or /Gz. However, the sample shows that there is a problem.
Sample Code
// TEST.H
class CMyclass
{
int * m_pinteger;
public:
operator const int *() const;
operator int();
};
// MAIN.CPP
/*
* Compiler options needed: /Gc for C/C++ for MS-DOS and Windows
* /Gz for C/C++ for Windows NT
*/
#include "test.h"
void __cdecl main(void)
{
CMyclass obj;
const int *y = obj;
const int z = obj;
}
// OTHER.CPP
/*
* Compiler options needed: None (omit /Gc and /Gz)
*/
#include "test.h"
CMyclass::operator const int *()const
{
return m_pinteger;
}
CMyclass::operator int()
{
return *m_pinteger;
}
Additional query words: 1.00 1.50 8.00 8.00c
Keywords: kbbug kbfix kbcpponly kbcompiler KB102619
