Solved

Problems with CString class of MFC

Posted on 2003-10-26
7
679 Views
Last Modified: 2013-12-14
Hi all

My application is an MFC dialog based server which calls ATL based dll's on client requests.

I have noticed that my application crashes when many user requests come and many times it gives unknown errors. My friend had said that there is a problem with MFC's CString class having memory leaks.

When i changed the ATL Based dll's to VB dll's it started working fine.

Can anyone please tell me if there is any problem in MFC's CString class or any other class.

Thanks.
0
Comment
Question by:sudeshsh
  • 2
7 Comments
 
LVL 23

Accepted Solution

by:
Roshan Davis earned 168 total points
ID: 9625525
Some problems Listed

1. An access violation may result after using CString::operator+= where the string on the right hand side of the operator is an empty string.

2. GP Fault when Use CString Objects Inside TRACE<x> Macros
eg:
    CString t1("output1");
   
    // Incorrect use of the %s format specifier with a CString object:
    TRACE1("TRACE1 %s\n", t1);

    // Correct is
    TRACE1("TRACE1 %s\n", (LPCTSTR)t1);


3. Chances of GP in *CString::Format* function- while using * (asterik) etc

4. If the CString equality operators (==, !=) are used in an attempt to test whether a CString is NULL, a general protection (GP) fault may occur. The following code fragment demonstrates this:


   CString x = "This is a sample CString";
   if (x != NULL)  // GP Fault for (x == NULL) condition, as well
      AfxMessageBox("The CString is not EMPTY");
   else
      AfxMessageBox("The CString is EMPTY");
Because x is a CString object, not a pointer, it is inappropriate to compare x to a null pointer.

Rosh :)
0
 
LVL 48

Assisted Solution

by:AlexFM
AlexFM earned 166 total points
ID: 9625535
>> When i changed the ATL Based dll's to VB dll's it started working fine.

This means, the problem is in dll's and not in your application?

About MFC CString class - you just try to guess. Whu CString and not something else? I never had problems with CString class.
0
 
LVL 23

Expert Comment

by:Roshan Davis
ID: 9625560
I think you are building the components in *Shared* DLLs, this makes problems.

Wrong versions of MFC DLLS (like MSVCRTxx.dll etc) in Client and Development machine makes problems.

To avoid this, Build your ATL DLL in *STATIC*

Rosh :)
0
 
LVL 8

Assisted Solution

by:martynjpearson
martynjpearson earned 166 total points
ID: 9625687
You say you have problems when "many users requests come". Could it be that you are not coordinating access to a CString so that two threads are accessing the same CString at the same time?

One other possible pitfall with CString is the use of GetBuffer() - after calling GetBuffer(), you must call ReleaseBuffer() before you do anything other CString operations.

Hope this helps
Martyn
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Unable to open debugger port in Intellij idea 6 147
mapBully challenge 6 114
Error E2158 compiling with Delphi XE10 Seattle 2 88
move one pixel 4 58
Whether you've completed a degree in computer sciences or you're a self-taught programmer, writing your first lines of code in the real world is always a challenge. Here are some of the most common pitfalls for new programmers.
If you’re thinking to yourself “That description sounds a lot like two people doing the work that one could accomplish,” you’re not alone.
THe viewer will learn how to use NetBeans IDE 8.0 for Windows to perform CRUD operations on a MySql database.
The viewer will learn how to use and create new code templates in NetBeans IDE 8.0 for Windows.

920 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now