Knowledge Base

FIX: Application Error If /Og & Virtual Operator Call in Loop

Article ID: 131000

Article Last Modified on 7/5/2005

Microsoft Visual C++ 2.0 Professional Edition
Microsoft Visual C++ 2.1

This article was previously published under Q131000

SYMPTOMS

An application error is generated when running a program that meets all these conditions:

It was compiled with global optimization (/Og).
It defines a virtual operator for a class.
It constructs an object of that class inside a loop.
The operator is called inside the loop.

CAUSE

The computation of the address of the virtual operator is being lifted out of the loop.

RESOLUTION

Use any one of the following four workarounds:

Move the object outside the loop. -or-
Use the functional form of the operator. -or-
If the operator does not need to be virtual, do not declare it virtual. -or-
Do not do global optimizations.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was fixed in Microsoft Visual C++, 32-bit Edition, version 4.0.

MORE INFORMATION

Sample Code to Reproduce Problem

/* Compile options needed: /Og
*/ 
class Test
{
public:
    virtual int operator <= ( const Test& T ) const {return 1;}
};

void main( void )
{
    long i;
    for (i=1; i<=3; i++)
    {
        Test T; //Work-around 1: Move this line above the for loop.
        T <= T; //Work-around 2: Comment out this line, uncomment the next.
        //T.operator<=(T); // Function form of the operator.
    }
}

Additional query words: 2.00 2.10 9.0 9.1 9.00 9.10

Keywords: kbbug kbfix kbcodegen kbcpponly kbcompiler KB131000