asked on

set_new_handler not working?

I'm trying to use a custom new_handler, in case the new operator cannot get enough memory for my object.
When I run the following code, instead of getting the error message I specify when I run out of memory, the program terminates with the output "Failed".

The code is:

#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;

int counter = 0;

void out_of_memory() {
cerr << "memory exhausted after " << counter
<< " allocations!" << endl;
exit(1);
}

int main() {
set_new_handler(&out_of_memory);
while(1) {
counter++;
int* ia = new int[1000]; // Exhausts memory
}
}

This code is from "Thinking in C++ 2nd Ed, Vol 1" by Bruce Eckel, available from www.BruceEckel.com (with slight modifications)

I'm running linux mandrake 9.0, and g++ version 3.2 (3.2-1mdk).

Can anyone explain why my program terminates without my new_handler being called?

thanks,

sacka

Salte

I wouldn't use iostream in a memory handler the way you do.

It will typically try to allocate memory and since it is already inside memory allocation (out_of_memory is called before the memory allocation is done) it will just give up and write 'Failed' instead of doing the output to cerr.

Try to use very basic I/O, if you're on unix stick to write(2, msg,strlen(msg)); to do your output inside out_of_memory.

In Win32 you can also use the same write(2,msg,strlen(msg)) since it won't do any new.

You can also try a simple printf(stderr, ..); it might allocate memory but as it is a C function it will use malloc and not new.

Since you are out of memory it indicates that the run time is in trouble. You then have 2 options, either use non-C++ functions to do your I/O OR you can in the early stage of your program allocate a huge block of memory:

char * safety = new char[8192];

Then when you're out of memory you first do a delete [] safety and then you do your cerr etc....

so:

char * safety = 0;

int main()
{
safety = new char[8192];
....
}

void out_of_memory()
{
delete [] safety;
cerr .....;
exit(1);
}

Alf

sacka

ASKER

Salte,

Thanks for your comment.

I tried using the safety method, with no success.
I also tried using printf, same thing.

Which header files do I need to include to call write(,,)? I couldn't find documentation that mentioned that function.

Is there something weird about my system? What results do you get running the code I posted initially? Or the code with your suggestions?

thanks,

sacka

ASKER CERTIFIED SOLUTION

Salte

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burcarpat

works perfectly under mingw/gcc 3.2 and under redhat 7.2 and gcc 3.2.2. what you have might be a compiler and/or a lib bug. try to upgrade to 3.2.2

-b

bcladd

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