Re: throwing out of memory exception in c++ doesnt work
From: Stephan (stephas_at_frogking.stephas.homelinux.org)
Date: 03/01/04
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Date: Mon, 01 Mar 2004 05:12:56 GMT
On Mon, 01 Mar 2004 04:30:48 +0000, Leor Zolman wrote:
>
>
> The subject of your post is "throwing out of memory exception in c++
> doesn't work", but you've done precisely what it takes to /prevent/ such an
> exception from ever being thrown: you've created and installed a
> new_handler that doesn't follow the rules of what a new_handler should do,
> which is one of the following ( I'm plagiarizing this from Dinkumware's C++
> Reference):
>
> make more storage available for allocation and then return
> call either abort() or exit(int)
> throw an object of type bad_alloc
>
> If you've got a reasonably healthy quantity of virtual memory available,
> though, it may take quite a while to thrash itself to exhaustion before it
> reaches the point of calling your new_handler, so let's speed things up a
> bit and add some exception handling:
>
> #include <iostream>
> #include <exception>
> #include <stdexcept>
>
> using namespace std;
>
> void out_of_mem() {
> cerr << "in out_of_mem: problem\n";
> throw bad_alloc();
> }
>
> int main() {
>
> set_new_handler(out_of_mem);
>
> try {
> while(1) {
> cout << "Top of loop" << endl;
> int * tst = new int[800000000]; // make this too much!
> if (!tst)
> cout << "end of loop: problem\n";
> }
> }
> catch (const exception &e)
> {
> cerr << "Caught: " << e.what() << endl;
> exit(1);
> }
>
> return 0; // not likely to get here!
> }
>
>
> Output (MSVC 7.1):
>
> Top of loop
> in out_of_mem: problem
> Caught: bad allocation
>
>
> So after you "handle" the exceptions and make sure your new_handler does
> one of the right things, you'll still have the virtual memory thrashing
> problem to contend with. I can't help you there, but you definitely want to
> do a better job of avoiding memory leaks than your test program did (yeah
> yeah, just kidding), and perhaps just "know" how much memory you can
> allocate before the thrashing commences and try to keep track of what
> you've allocated.
>
> Good luck,
> -leor
>
> Leor Zolman
> BD Software
> leor@bdsoft.com
> www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix
> C++ users: Download BD Software's free STL Error Message
> Decryptor at www.bdsoft.com/tools/stlfilt.html
thanks for the quick post!!
and your code seems to make a lot more sense now, and the exception gets
thrown, when allocating the array of ints, but I am trying to allocate a
couple small int arrays, and than it will just say Killed and I have no
ide why it didnt go into the handler.
thanks for the good try block/catch block example (although I have no idea
where the exception data type comes from, and I guess I want to avoid it?)
thx
Stephan
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