Problem with delete operator

[felixb]

Hello,

I have a source code like this:

void func()
{
char* str;
str=new char[5*sizeof(char)];
.
.
.
delete line;
}

When the program get to the "delete line", It shows the following error:
Debug assertion failed!
expression: _BLOCK_TYPE_IS_VALID(phead->nblockuse)

Why does I get the error message?
As I understand, I can use the delete operator for every varabile that was allocated with the "new" operator...

Thnk you,

[laserlight]

Match new with delete and new[] with delete[].

On the other hand, if you are going to create an array of exactly 5 chars and destroy it at the end of the function, you might as well write:

char str[5];
// ...

[Emerald214]

If you want an array with 5 chars, you should use:

char a[5]; // allocated on stack, no need delete

or

char *a = new char[5]; // allocated on heap
delete a;

[VladimirF]

char* str;
str=new char[5*sizeof(char)];
.
.
.
delete line;

Why does I get the error message?

Because you new "str" and delete "line"?

[Richard.J]

If you want an array with 5 chars, you should use:

char *a = new char[5]; // allocated on heap
delete[] a;

see laserlight's post

[felixb]

it's just an example, I haven't posted the full source.
In the full source, it isn't "char[5*sizeof(...)" but it is: "char[i*sizeof(...)]", so I do need dynamic allocation here.

I changed the source to this:
void func()
{
char* str;
str=new char[5*sizeof(char)];
.
.
.
delete[] str;
}

But I still receive the assertion error.

[Richard.J]

then, as the usual requirement, post the minimal complete code to reproduce the problem.

[Lindley]

it's just an example, I haven't posted the full source.
In the full source, it isn't "char[5*sizeof(...)" but it is: "char[i*sizeof(...)]", so I do need dynamic allocation here.

Is there some reason why a std::string or std::vector<char> won't work?

[monarch_dodra]

Don't use "new" with "sizeof". new is not malloc. If you need 5 new objects, then new will create 5 of these objects, regardless of their size.

for example:

int* integers = new int[5*sizeof(int)];

Most likely, you will actually create 20 ints.

[felixb]

this is the full code:

char** conv(int* size,char** a,char* b[])
{
char* line;
int m=0,l=0;
int curr,next;

line=new char[m*sizeof(char)];
a=new char*[l*sizeof(char)];

for(int i=1;i<*size;i++)
{
while(i<*size && (strcmp(*(&b[i]),"end") != 0))
{
curr=strlen(line);
next=strlen(b[i]);
line=realloc_func(line,curr,curr+next);
strcat(line,b[i]);
i++;
}
line[strlen(line)+1]='\0';
text=realloc_func(a,l);
text[m]= new char[m+1];
strcpy(a[l],line);
l++;
}

*size=l;

delete[] line;
return a;
}

(realloc_func - is function that get some pointer to array and increase it, by creating bigger one and copying the old to the new)

I get the error when I reach the "delete[] line" ...

[Richard.J]

from what you posted here I'd say the problem is inside the realloc_func. What exactly does that do (in code)?

[jnmacd]

int m=0,l=0;
int curr,next;

line=new char[m*sizeof(char)];
a=new char*[l*sizeof(char)];

m and l are both zero.
So you aren't creating memory, not even sure what the result of this is

[Paul McKenzie]

this is the full code:

You didn't answer a question that was asked of you in a previous post. Why not just use std::string (or std::vector<char>), instead of fooling around with new[], delete[], strcat(), char pointers, etc.?

What exactly are you trying to accomplish with this code? In C++,, you have the std::string class that does everything that your code is trying to do.

Regards,

Paul McKenzie