Microsoft KB Archive/170514

= FIX: Bad Codegen with /Og and Floating-Point Multiplication Class with Virtual Destructor =

Article ID: 170514

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition

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This article was previously published under Q170514



SYMPTOMS
The Visual C++ 5.0 compiler may generate incorrect instructions when it encounters floating-point multiplication in a member of a class that has a virtual destructor.



RESOLUTION
Use one of the following four workarounds:


 * Use /Op.
 * Do not use /Og. Note that /O1, /O2, and /Ox are aggregate optimization switches that include /Og.
 * Use the optimize pragma around the class member to disable the /Og optimization or to turn on the /Op optimization.
 * Make the destructor non-virtual. This may not be an option if the given class is derived from a class that has a virtual destructor in a library that you cannot change.



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was corrected in Visual C++ 5.0sp3.



Steps to Reproduce Behavior
// Compile options needed to reproduce the bug: /Og // Compile options needed to work around the bug: /Og /Op

#include   #include 

struct A {

double   m_X; double   m_Y;

};

typedef double rg23[2][3];

struct B   {

rg23 m;      B(double rotn = 0); void func(double *px, double *py) const; virtual ~B{}

};

B::B(double rotn) {

double cosa = cos(rotn); double sina = sin(rotn);

m[0][0] = m[1][1] = cosa; m[0][1] = -sina; m[1][0] = sina; m[0][2] = m[1][2] = 0;

}

void B::func(double *px, double *py) const {      double x = *px; double y = *py; *px = x * m[0][0] + y * m[0][1] + m[0][2]; *py = x * m[1][0] + y * m[1][1] + m[1][2]; }

int main {

A a;      a.m_X=1.0; a.m_Y=2.0;

printf("Values in: x=%lf; y=%lf\n", a.m_X, a.m_Y);

B ct; ct.func(&a.m_X, &a.m_Y);

printf("Values out: x=%lf; y=%lf\n", a.m_X, a.m_Y);

return 0;

}

Expected Output
  Values in: x=1.000000; y=2.000000 Values out: x=1.000000; y=2.000000

Actual Output
  Values in: x=1.000000; y=2.000000 Values out: x=1.000000; y=0.000000

Keywords: kbbug kbfix kbvc600fix kbcode KB170514

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