Programming Forums > Application Development > C++

myName · May 23rd, 2006, 4:06 AM

When the function below is being execute, a debug assertion Failed error occur where a microsoft Visual C++ Debug Library Dialog Box exist.

Quote:

Debug Assertion Failed!

Program: C:\test\Debug\a.exe
Filedbgdel.cpp
Line:47

Expression:_BLOCK_TYPE_IS_VALID(pHead->nBlockUse)

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 void function1()
{
	char *c = NULL;

	c="Jay";

	cout<<c<<endl;

	if(c)
	 delete c;
}

hbe02 · May 23rd, 2006, 4:36 AM

Quote:

char *c = NULL;

try this:

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char *c = new char [size]

size is an integer .. here you are saying ... create c , which is a pointer to an array of characters of size[size]..

myName · May 23rd, 2006, 4:49 AM

Hi hbe02,

Tried. Can not. :-(

nnxion · May 23rd, 2006, 5:08 AM

I suggest you use C++ strings, like:

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#include <iostream>
#include <string>

using namespace std;

void function1()
{
	string c;

	c = "Jay";

	cout << c << endl;
}

int main()
{
	function1();
	return 0;
}

But here's C strings for you anyway:

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#include <iostream>
#include <cstring>

using namespace std;

void function1()
{
	char *c = NULL;
	c = new char[strlen("jay") + 1];

	c = "Jay";

	cout << c << endl;

	delete [] c;
}

int main()
{
	function1();
	return 0;
}

Cache · May 23rd, 2006, 8:00 AM

Then assertion failed because you are calling delete on a pointer that doesn't point to dynamically allocated memory.

Quote:

Originally Posted by myName

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 void function1()
{
	char *c = NULL;

	c="Jay";

	cout<<c<<endl;

	if(c)	// Note: c != 0 == true.
	 delete c;  // <--- Oops!
}

DaWei · May 23rd, 2006, 8:06 AM

Did you mean to use strcpy up there, Ruben?

A personal opinion about NULL. There's little use setting a declared pointer to NULL if the very next line is going to assign to it. I WOULD test it afterward, to make sure my request got fulfilled.

At the OP. Strings, as suggested by Ruben, are a good idea. I would still suggest that you read the material on pointers that is referenced in my signature. It won't help you understand about not paying back memory you didn't borrow, though, as Cache pointed out. You'll have to get that elsewhere.

nnxion · May 23rd, 2006, 1:20 PM

Quote:

Originally Posted by DaWei

Did you mean to use strcpy up there, Ruben?

Whoops, yeah, I was just trying to show what he was trying, I didn't actually think about what the code was doing.

MY BAD, don't try that at home. :p

May 23rd, 2006, 5:08 AM	#4
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	I suggest you use C++ strings, like: (Toggle Plain Text) #include <iostream> #include <string> using namespace std; void function1() { string c; c = "Jay"; cout << c << endl; } int main() { function1(); return 0; } #include <iostream> #include <string> using namespace std; void function1() { string c; c = "Jay"; cout << c << endl; } int main() { function1(); return 0; } But here's C strings for you anyway: (Toggle Plain Text) #include <iostream> #include <cstring> using namespace std; void function1() { char c = NULL; c = new char[strlen("jay") + 1]; c = "Jay"; cout << c << endl; delete [] c; } int main() { function1(); return 0; } #include <iostream> #include <cstring> using namespace std; void function1() { char c = NULL; c = new char[strlen("jay") + 1]; c = "Jay"; cout << c << endl; delete [] c; } int main() { function1(); return 0; } __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

May 23rd, 2006, 8:06 AM	#6
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Did you mean to use strcpy up there, Ruben? A personal opinion about NULL. There's little use setting a declared pointer to NULL if the very next line is going to assign to it. I WOULD test it afterward, to make sure my request got fulfilled. At the OP. Strings, as suggested by Ruben, are a good idea. I would still suggest that you read the material on pointers that is referenced in my signature. It won't help you understand about not paying back memory you didn't borrow, though, as Cache pointed out. You'll have to get that elsewhere. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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May 23rd, 2006, 4:49 AM	#3
myName Programmer Join Date: Oct 2005 Posts: 48 Rep Power: 0	Hi hbe02, Tried. Can not. :-(

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