strcpy causing my Win32 program to crash upon exit 1

[MinnisotaFreezing]

Hello,
Here is my program in its entirety, with the exception of stdafx.cpp, which is not used.
[ccode]
#include "stdafx.h"
#include <string.h>

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{

char * pbuff = &quot;C:/Documents and Settings/dynacom/Local Settings/Application Data/Microsoft/Outlook/&quot;;
char text[] = &quot;The Outlook file was not transferd because:&quot;;
char * errortext = &quot;ERROR&quot;;
BOOL ret;
ret = CopyFile(pbuff, &quot;\\Mainroom/Outlook/Dave/Dave.pst&quot;, FALSE);
if (!ret)
{
LPVOID lpMsgBuf;
FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS, NULL, GetLastError(), 0,(LPTSTR) &lpMsgBuf,0,NULL);
//strcat(text, (LPCTSTR)lpMsgBuf);
strcat(text, errortext);
MessageBox(NULL, text, NULL, 0);
MessageBox(NULL, text, &quot;ERROR&quot;, 0);
}

return 0;
}
[/ccode]
The problem lies with the commented strcat line. When I uncommend the line, the program crashes on exit. I step through using the debugger, past the return 0;, to the last bracket, when it crashes with the &quot;Memory could not be &quot;read&quot;&quot; message. The strcat function does what I expect, in debug the variable text is appended as I wanted. Does anyone have any info about this? I have very little experience with LPVOID types, so I am sure my mistake lies there. I hope I explained this halfway decent, I've been wrestling with this for a while. I made the offending line red.

To me this seems very strange. If you want, you could copy the code right from here, past it into a new simple Win32 Application, and it should run. Uncomment the line, and it will crash not on the now uncommented line, but on exit.

Thank you for your help,

CJB

 

[brudnakm]

MinnisotaFreezing,

It appears that there are a few things worth correcting:

1) text[] is allocated exactly enough space for its initialization string. strcat() will write outside of this allocated space an possibly corrupt the stack, other local variables, or information necessary for a safe return. When you use the initiialization char text{} = &quot;xxxx&quot;. You should not use text for anything other than as a constant.

2) lpMsgBuf is also allocated on the stack as a local variable. The compiler may allocate its space at function entry as an optimization. Therefore the text[] overflow may affect it too.

The bottom line is that text[] is overflowing because of its allocation and the strcat. This corrupts the stack which can cause many weird errors.

Brudnakm

 

[MinnisotaFreezing]

Brudnakm,
Thanks for the help. That explians why I was getting some other wierd errors before as well. But let me ask you, what would you suggest to fix this problem? I tried:

char   text[50] = "The Outlook file was not transferd because:";
char * ptext = text;
strcat(ptext, (LPCTSTR)lpMsgBuf);

but I got the same error. Do I really have to find the length of both strings and then create a new buffer of that size to use? I'll admit, my pointers are a little rusty because of CString, but I didn't think it was that hard to cat a string.

It does work if I just create my first array size [100] and hope I don't go over it when I strcat, but I'd rather not.

Again, any help is appriciated.

CJB

 

[chiph]

Do I really have to find the length of both strings and then create a new buffer of that size to use?

To be 100% correct, yes you should. But most people simply allocate a larger buffer (like you suggested) and hope they don't overflow it. I usually use the MAX_PATH constant.

Chip H.