malloc

[farshid]

I have written a long program with c, and am using dynamic memory allocation. This program is supposed to be run over and over (300 times) for a long simulation. But the program stops after 120 cycles due to memory leackage. I am not very expert in programing but it seems that my free() function does not do anything to my program. One example of how I do memory allocation and free is this:

int *D;
D= (int *) malloc(size).

void myfunction{

I use D here;
free(D);
...
}

void main()
{
...

myfunction();

}

When I disable "free();" there is no difference in memory consumption, and it stops at cycle 120 again. Is there anything wrong with the way I allocate memory to D or free it.

Thanks and looking forward to hearing from you soon.

Farshid

[farshid]

malloc

Hello,

I have written a long program with c, and am using dynamic memory allocation. This program is supposed to be run over and over (300 times) for a long simulation. But the program stops after 120 cycles due to memory leackage. I am not very expert in programing but it seems that my free() function does not do anything to my program. One example of how I do memory allocation and free is this:

int *D;
D= (int *) malloc(size); //D is a global pointer for some functions

void myfunction()
{

//I use "D" here and some other fucntions which are called here.

//then I free D.


free(D);
...
}

void main()
{
...

myfunction();

}

When I disable "free();" there is no difference in memory consumption, and it stops at cycle 120 again. Is there anything wrong with the way I allocate memory to D or free it?

Thanks and looking forward to hearing from you soon.

Farshid

[dtimes6]

what compiler are you using ? gcc can not work in that way.

[Banfa]

Please don't double post.

This line

D= (int *) malloc(size); //D is a global pointer for some functions

is invalid outside a function, this wont compile.

[farshid]

Sorry,
D= (int *) malloc(size); is in a function called init(). But the pointer declaration "int *D" is not in a fucntion. The program works, but it stops sooner than I need to.

Please don't double post.

This line

D= (int *) malloc(size); //D is a global pointer for some functions

is invalid outside a function, this wont compile.

[farshid]

I use gcc. There was a mistake in that example. actually the line D= (int *) malloc(size); is inside a function called init(). the rest are ok. I don't know why my program eats up the memory. whether or not I free the memory it uses all of it very fast.

what compiler are you using ? gcc can not work in that way.

[tyreld]

Can you please post the chunck of code from this init function? In particular I'm curious where you define the size value you are passing to malloc.

[farshid]

Can you please post the chunck of code from this init function? In particular I'm curious where you define the size value you are passing to malloc.

here is a copy paste of some part of my code

int *D;

void init()
{
int sizealloc, sch_size,node_s ize, i;
sizealloc = (2*nodes+2)*(si zeof(int));
node_size = nodes*nodes *(sizeof(int));
D = (int *) malloc(node_siz e);

....
}

[tyreld]

What platform are you compiling running this on? There are various malloc debuggers available for tracing memory leaks and various other memory management errors. Valgrind and ElectricFence are two such examples available on Linux.

[farshid]

What platform are you compiling running this on? There are various malloc debuggers available for tracing memory leaks and various other memory management errors. Valgrind and ElectricFence are two such examples available on Linux.

oh, I don't know. I am using a c/c++ based software for simulating networks. The software is installed on windows xp, and I do not know how to trace memory leaks.

[tyreld]

You can start by simply adding some debugging printf's. Insert one before each call to malloc printing out the node_size being requested. Insert one before every free operation making sure you have a matching number of free calls for every malloc. The goal is to see how much memory you are requesting at each call, and to ensure you are properly releasing the memory before you allocate new memory.

Also, how is the program failing? Is malloc eventually returning a NULL value, or is the program crashing?

[farshid]

You can start by simply adding some debugging printf's. Insert one before each call to malloc printing out the node_size being requested. Insert one before every free operation making sure you have a matching number of free calls for every malloc. The goal is to see how much memory you are requesting at each call, and to ensure you are properly releasing the memory before you allocate new memory.

Also, how is the program failing? Is malloc eventually returning a NULL value, or is the program crashing?

Thanks for the tips. The program returns a message which I think was generated by the software:

Allocation of memory failed;

[tyreld]

Are you using the stdlib version of malloc, or are you using a malloc implementation from some sort of seperate c/c++ framework?

[farshid]

Are you using the stdlib version of malloc, or are you using a malloc implementation from some sort of seperate c/c++ framework?

I have tried malloc from stdlib before, eventhough I use the malloc implementation of the software now, but there is no difference when I convert them to malloc of stdlib.

by the way, I counted the allocation and free calls and they were both equal.

[tyreld]

Are the size of your memory allocations constant over time? Is this the only dynamic memory allocation taking place? Are you using any recursion?