Thread: Error Message when run program

When running my program I get an error message that says this:

Debug Error!

HEAP CORRUPTION DETECTED: before Normal block(#1262858) at 0x268F3148.
CRT detected that the application wrote to memory before start of heap buffer.

What could this meen. Sometimes when running the program this error doesn´t come up and sometimes it does.

It is to much code to present here but what I do is to read .txt files into vectors and 2D vectors.
I know it perheps is difficult to know what it could depend on, but any idéas, guesses is welcome on this one.
I dont really dont know where to begin my search in the code.

If you are using an index in a vector or string that is invalid you might get something like that. Use at() instead of [] and you will get an exception that might help you identify the source of the problem.

Also, you should be able to debug your program and look at the call stack to see where in your code this corruption is occurring. Then you can post just that code and whatever is relevant to it so we can take a look.

sorry if asking but what is the "call stack". Is this something inside VC++ that creates when just debugging the program and not run it ?

Yes. When you run your program through the debugger (in VC++ that's F5 to Start or Run, not Ctrl-F5 or Execute), one of the windows that you can open is the Call Stack. When you get the error you mentioned or any other unhandled exception, VC++ will stop the program and you can view where it occurred and what the data is in the location that is being executed.

So try running it instead of executing it, then do whatever you need to do to get the error to occur. When it gives you the option you should break and then find the call stack window and look for code that you wrote and recognize. Then double click on that code and it should take you to about the place where the error is occurring.

So look in the call stack window and there should be something below that line that comes from your code. Double click on the line that is in your code.

That's the call stack. It means that each function is calling the function above it. The one on the bottom appears to be your code? Scroll down to the line that has the code you wrote and only double-click that line.

If you haven't written any of them, at least you should recognize some, like the bottom one, which references Form3 and an Optimize_Click function.

By the way, you should make it clear if you are using Forms and .NET programming or C++/CLI or whatever that is. That isn't standard C++ and is covered that often in this forum. I probably won't be able to help much because I know little to nothing about the interaction of a standard C++ container like vector and System and Form stuff.

you using .NET or something? I never use .NET, but for c at the beginning of your code you could try adding

#define new new(__FILE__, __LINE__)

which should provide file and line information to the debug heap when running in debug mode which would result in something like:

Code:

 			 				Debug Error!

HEAP CORRUPTION DETECTED: before Normal block(#1262858) at 0x268F3148.
CRT detected that the application wrote to memory before start of heap buffer.  File: c:\[whatever dir your code in is]\[filename error occurred].cpp (5)

Where that (5) in parenthesis would be where the initial memory that is causing the corruption would be found

i.e.

Code:

line#5: float *a = new float[10]; <--- the originally memory that got corrupted.
...
line#500 memset(a - 1, 0,  sizeof(float) * 10) <--- follow the var "a" to find the corruption, which occurred here.

Your error sounds like the result of pushing a [non-dynamically allocated] variable onto a "vector" and then modifying it using pointers or incorrectly using one of the c++ standard library functions like strn_cpy(); printf(); etc. on it and then sometime down the line when you goto remove that item from the "vector" it tries to deallocate it, but can't because the memory block is screwed.

Yes, I use .NET. Thank you for the information. I am not sure if I understand how to use
#define new new(__FILE__, __LINE__) correctly but I think you are right about:
"pushing a [non-dynamically allocated] variable onto a "vector" "

Sometimes I use push_back for vectors and sometimes not. I am just giving them a size and start put strings and int:s, doubles to the elements using count = (count + 1).

Then I do sort these vectors and something might go wrong here. Though sometimes I can run my program as I did a test yesterday, with the exact same procedure, over 60 times in a row and then the Error came up. So the program works but at the same time not.
So not using push_back perheps can cause Errors like this ?
Thanks

>> So not using push_back perheps can cause Errors like this ?
If you access positions that don't exist, then yes. But you can do that with push_back, too.

The problem is occuring when a vector is being destroyed in the Form3::Optimize_Click function. Is there a local vector inside there? Was there anything else lower in the call stack?