BUG: CV: Trace Does Not Step Into Some MOVE Overlay Functions

The information in this article applies to:

• Microsoft Codeview for MS-DOS, versions 4.0, 4.01, and 4.1

SYMPTOMS

Codeview may not allow tracing into some functions if the order of functions within a project's .DEF file is not the same as the order in which the functions are defined in the project's source files. Once this happens, it also may not be possible to view the source in the corresponding module. The code itself, however, executes properly.

RESOLUTION

To work around this problem, make sure that functions are assigned to overlays in the .DEF file in the same order in which they are defined in the source files.

STATUS

Microsoft has confirmed this to be a problem in Codeview for MS-DOS, version 4.0, 4.01, and 4.1. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The sample program shown below can be used to demonstrate the problem. After building a debug version of the program, start Codeview, load the .EXE, and press F8 three times. Codeview will not step into the first function, Overlay1Func1(). Codeview will, however, step into Overlay1Func2() and Overlay1Func3. Also, at this point the VS command (View Source) does not work on Overlay1Func1().

Sample Code

/*  OVERLAY.H
*/

int Overlay1Func1(void);
int Overlay1Func2(void);
int Overlay1Func3(void);
int Overlay2Func1(void);
int Overlay2Func2(void);
int Overlay2Func3(void);

/*  MAIN.C

    Compile options needed:  /c /AL /G2 /Gy /Zi /Od
*/

#include "overlay.h"

void main( void )

    Overlay1Func1();
    Overlay1Func2();
    Overlay1Func3();
    Overlay2Func1();
    Overlay2Func2();
    Overlay2Func3();

/*  OVERLAY1.C

    Compile options needed:  /c /AL /G2 /Gy /Zi /Od
*/

#include "overlay.h"

int Overlay1Func1(void)

    int i = 1;
    i = i * 2;
    return i;

int Overlay1Func2(void)

    int i = 2;
    i = i * 2;
    return i;

int Overlay1Func3(void)

    int i = 3;
    i = i * 2;
    return i;

/*  OVERLAY2.C

    Compile options needed:  /c /AL /G2 /Gy /Zi /Od
*/

#include "overlay.h"

int Overlay2Func1(void)

    int i = 1;
    i = i * 2;
    return i;

int Overlay2Func2(void)

    int i = 2;
    i = i * 2;
    return i;

int Overlay2Func3(void)

    int i = 3;
    i = i * 2;
    return i;

;; OVERLAY.DEF

FUNCTIONS:1 _Overlay1Func2

            _Overlay1Func3
            _Overlay1Func1 ;;  Moving this above Overlay1Func2
                           ;;  solves the problem

            _Overlay2Func2
            _Overlay2Func3