throwing out of memory exception in c++ doesnt work

[Stephan]

why does the following code not work????
after compiling and running it will just say killed after all my memory
filled up
any suggestions?
#include <iostream>
using namespace std;

void out_of_mem() {
cout << "problem\n" ;
}

// void ?
int main() {

set_new_handler (out_of_mem);

while(1) {
int * tst = new int[1024];
if (!tst)
cout << "problem\n" ;
}

[Leor Zolman]

On Mon, 01 Mar 2004 03:45:44 GMT, Stephan
<st*****@frogki ng.stephas.home linux.org> wrote:

why does the following code not work????
after compiling and running it will just say killed after all my memory
filled up
any suggestions?

#include <iostream>
using namespace std;

void out_of_mem() {
cout << "problem\n" ;
}

// void ?
int main() {

set_new_handler (out_of_mem);

while(1) {
int * tst = new int[1024];
if (!tst)
cout << "problem\n" ;
}

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
le**@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

[Stephan]

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
le**@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

[Leor Zolman]

On Mon, 01 Mar 2004 05:12:56 GMT, Stephan
<st*****@frogki ng.stephas.home linux.org> wrote:

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.
If you're not allocating much memory and your program crashes, I doubt the
crash is related to exhaustion of the free store! Pointer bug? Have a
debugger you can fire up and trace through the program with? Why do you
think the issue is dynamic-memory-allocation-failure related?
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?)
You mean bad_alloc? That's from <stdexcept> ("Standard exceptions"). If
you're not all that familiar with the exception handling mechanism and/or
debugging techniques, I highly recommend the first few chapters of
Eckel/Allison's _Thinking in C++ Volume 2_, a free download at
www.mindview.net

Good luck,
-leor
thx
Stephan

Leor Zolman
BD Software
le**@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

[Stephan]

On Mon, 01 Mar 2004 05:41:20 +0000, Leor Zolman wrote:

On Mon, 01 Mar 2004 05:12:56 GMT, Stephan
<st*****@frogki ng.stephas.home linux.org> wrote:

If you're not allocating much memory and your program crashes, I doubt the
crash is related to exhaustion of the free store! Pointer bug? Have a
debugger you can fire up and trace through the program with? Why do you
think the issue is dynamic-memory-allocation-failure related?
gdb just tells me:
Program terminated with signal SIGKILL, Killed.
I didnt kill it and gdb doesnt report a line number, and gtkrellm shows
that my memory is filling up until the SIGKILL interrupts.
You mean bad_alloc? That's from <stdexcept> ("Standard exceptions"). If
you're not all that familiar with the exception handling mechanism
and/or debugging techniques, I highly recommend the first few chapters
of Eckel/Allison's _Thinking in C++ Volume 2_, a free download at
www.mindview.net

Good luck,
-leor

thx
Stephan
Leor Zolman
BD Software
le**@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

I am pretty familiar with the above, and I meant the actual exception data
type you wrote here: catch (const exception &e)

I think this is the type for any OS thrown exceptions, since you can throw
your own int, char, whatever ones. I guess I answered my own question.

However I am still unsure about why I get a SIGKILL ! If I leave your try
and catch block out and dont throw the bad_alloc(), I ll be stuck in an
endless loop but I can't even see that more memory is used in gtkrellm,
which shows how much memory is currently in use.
thanks
stephan

[Leor Zolman]

On Mon, 01 Mar 2004 06:08:18 GMT, Stephan
<st*****@frogki ng.stephas.home linux.org> wrote:

On Mon, 01 Mar 2004 05:41:20 +0000, Leor Zolman wrote:

If you're not allocating much memory and your program crashes, I doubt the
crash is related to exhaustion of the free store! Pointer bug? Have a
debugger you can fire up and trace through the program with? Why do you
think the issue is dynamic-memory-allocation-failure related?

gdb just tells me:
Program terminated with signal SIGKILL, Killed.
I didnt kill it and gdb doesnt report a line number, and gtkrellm shows
that my memory is filling up until the SIGKILL interrupts.

Good, intuitive debuggers can be hard to find on Unix...but there's always
good 'ole cerr. As a last resort I begin putting in trace statements. There
are some great tricks for doing that sort of thing in the Eckel/Allison
book I cited. You need a better handle on where the code is when it
crashes.
I am pretty familiar with the above, and I meant the actual exception data
type you wrote here:

catch (const exception &e)I think this is the type for any OS thrown exceptions, since you can throw
your own int, char, whatever ones. I guess I answered my own question.

Yeah, basically all standard exceptions derive from "exception" ; in this
case I did that to gain access to the what() member function. If I didn't
care about that, I would probably just have used catch(...)
-leor

However I am still unsure about why I get a SIGKILL ! If I leave your try
and catch block out and dont throw the bad_alloc(), I ll be stuck in an
endless loop but I can't even see that more memory is used in gtkrellm,
which shows how much memory is currently in use.
thanks
stephan

Leor Zolman
BD Software
le**@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

[Chris \( Val \)]

"Leor Zolman" <le**@bdsoft.co m> wrote in message
news:kc******** *************** *********@4ax.c om...
| On Mon, 01 Mar 2004 03:45:44 GMT, Stephan
| <st*****@frogki ng.stephas.home linux.org> wrote:
|
| >why does the following code not work????
| >after compiling and running it will just say killed after all my memory
| >filled up
| >any suggestions?
| >
| >#include <iostream>
| >using namespace std;
| >
| >void out_of_mem() {
| > cout << "problem\n" ;
| >}
| >
| >// void ?
| >int main() {
| >
| > set_new_handler (out_of_mem);
| >
| > while(1) {
| > int * tst = new int[1024];
| > if (!tst)
| > cout << "problem\n" ;
| > }

[snip]

C'mon Leor :-).

You know that 'new' does not return '0' unless you tell it to:

int * tst = new ( std::nothrow )int[ 80000000 ];

Oh, and don't forget to break out of the 'if' statement.

Cheers.
Chris Val

[Leor Zolman]

On Tue, 2 Mar 2004 01:00:44 +1100, "Chris \( Val \)"
<ch******@bigpo nd.com.au> wrote:

"Leor Zolman" <le**@bdsoft.co m> wrote in message
news:kc******* *************** **********@4ax. com...
| On Mon, 01 Mar 2004 03:45:44 GMT, Stephan
| <st*****@frogki ng.stephas.home linux.org> wrote:
|
| >why does the following code not work????
| >after compiling and running it will just say killed after all my memory
| >filled up
| >any suggestions?
| >
| >#include <iostream>
| >using namespace std;
| >
| >void out_of_mem() {
| > cout << "problem\n" ;
| >}
| >
| >// void ?
| >int main() {
| >
| > set_new_handler (out_of_mem);
| >
| > while(1) {
| > int * tst = new int[1024];
| > if (!tst)
| > cout << "problem\n" ;
| > }

[snip]

C'mon Leor :-).

You know that 'new' does not return '0' unless you tell it to:

int * tst = new ( std::nothrow )int[ 80000000 ];
You know, I originally was going to pursue that part of it and got
completely sidetracked by the exception behavior aspects of this...so I
stopped thinking about that code after the new operation because I figured
it would never be reached! Duh. I'm still definitely on a learning curve
when it comes to my "mental checklist" of things to look out for in these
posts!
Thanks Chris,
-leor

Oh, and don't forget to break out of the 'if' statement.

Cheers.
Chris Val

Leor Zolman
BD Software
le**@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

[Chris \( Val \)]

"Chris ( Val )" <ch******@bigpo nd.com.au> wrote in message
news:c1******** *****@ID-110726.news.uni-berlin.de...
|
| "Leor Zolman" <le**@bdsoft.co m> wrote in message
| news:kc******** *************** *********@4ax.c om...
| | On Mon, 01 Mar 2004 03:45:44 GMT, Stephan
| | <st*****@frogki ng.stephas.home linux.org> wrote:
| |
| | >why does the following code not work????
| | >after compiling and running it will just say killed after all my memory
| | >filled up
| | >any suggestions?
| | >
| | >#include <iostream>
| | >using namespace std;
| | >
| | >void out_of_mem() {
| | > cout << "problem\n" ;
| | >}
| | >
| | >// void ?
| | >int main() {
| | >
| | > set_new_handler (out_of_mem);
| | >
| | > while(1) {
| | > int * tst = new int[1024];
| | > if (!tst)
| | > cout << "problem\n" ;
| | > }
|
| [snip]
|
| C'mon Leor :-).
|
| You know that 'new' does not return '0' unless you tell it to:
|
| int * tst = new ( std::nothrow )int[ 80000000 ];
|
| Oh, and don't forget to break out of the 'if' statement.

Actually - I just realised, this test is wrong :-).

Even if we use the 'std::nothrow', it will no longer
throw 'std::bad_alloc ', but rather, it will return 0,
and this will bypass 'std::set_new_h andler'.

Better to avoid the 'if' expression completely, and
redesign the test case :-).

# include <iostream>
# include <ostream>
# include <new>

void MyHandler()
{
std::cout << "MyHandler Called... " << std::endl;
throw std::bad_alloc( );
}

int main()
{
std::set_new_ha ndler( MyHandler );

try
{
for( int Idx( 0 ); Idx < 1000000; ++Idx )
new char[ Idx * Idx ];
}
catch( const std::bad_alloc& e )
{
std::cout << e.what() << std::endl;
}

std::cin.get();
return 0;
}

Cheers.
Chris Val

[Chris \( Val \)]

"Leor Zolman" <le**@bdsoft.co m> wrote in message
news:kp******** *************** *********@4ax.c om...
| On Tue, 2 Mar 2004 01:00:44 +1100, "Chris \( Val \)"
| <ch******@bigpo nd.com.au> wrote:

[snip]

| >int * tst = new ( std::nothrow )int[ 80000000 ];
|
| You know, I originally was going to pursue that part of it and got
| completely sidetracked by the exception behavior aspects of this...so I
| stopped thinking about that code after the new operation because I figured
| it would never be reached! Duh. I'm still definitely on a learning curve
| when it comes to my "mental checklist" of things to look out for in these
| posts!

I know the feeling, I feel like that now - need serious shut eye :-).

Cheers.
Chris Val