Allocation of large amount of memory gives error ? Why?

Question

I have made a application for high resolution images.

when I want to allocate large amount of memory, the system says "Application has requested the Runtime to terminate it in an unusual way." But what I want is, the allocated pointer must return 0 Or NULL that I can show my message. It does not return zero/NULL why ? any idea? I checked with debug, before proceeding to MessageBox, it gives this error. what to do here to display my message ?

And is there a way to check that the user is going to allocate large enough memory than the computer PC capacity ?

Thanks.

ImageW = 2000;
ImageH = 2000;
point *Img = NULL;
Img = new point[ImageW*ImageH];
if(Img== NULL)
{   
MessageBox(0, "Your computer memory is too small.", "Error", MB_ICONERROR | MB_OK);
return; 
}

Use nothrow version of new: http://stackoverflow.com/questions/7277637/new-stdnothrow-vs-new-within-a-try-catch-block — marcinj, Oct 16 '12 at 02:00
I pity the computer that doesn't have [what I imagine to be] 12MB spare of memory. — Lightness Races in Orbit, Oct 16 '12 at 02:01

Alexander Kondratskiy · Answer 1 · 2012-10-16T02:04:47.170

5

Unlike malloc in C which returns NULL on failure, new in C++ can throw a std::bad_alloc exception which is what you're seeing. See http://en.cppreference.com/w/cpp/memory/new/operator_new for reference

To handle this exception you can use try/catch:

try {
    Img = new point[ImageW*ImageH];
}
catch (std::bad_alloc const& e) {
    // handle failure here, like displaying a message
}

Here's documentation for the std::bad_alloc exception: http://en.cppreference.com/w/cpp/memory/new/bad_alloc

edited Oct 16 '12 at 02:04

answered Oct 16 '12 at 01:54

Alexander Kondratskiy

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how to about this .. And is there a way to check that the user is going to allocate large enough memory than the computer PC capacity ? .. then what is the solution to display our own message ? – maxpayne Oct 16 '12 at 01:56
@furqan Edited my answer on how to handle this. – Alexander Kondratskiy Oct 16 '12 at 01:59
1

"You must use try/catch" Not true - look up `nothrow` – Lightness Races in Orbit Oct 16 '12 at 02:00
@LightnessRacesinOrbit sure, I said "you must use try/catch" to handle the bad_alloc exception. – Alexander Kondratskiy Oct 16 '12 at 02:07
yea nothrow is working but creating a new name.lib file ? what is this.. and it will be included in the setup MSI build or not? – maxpayne Oct 16 '12 at 02:14

score 5 · Accepted Answer · answered Oct 16 '12 at 01:59

5

Use nothrow:

Img = new (nothrow) point[ImageW*ImageH];
//        ^^^^^^^^^^

Now you get a null pointer, rather than an exception, if the allocation failed.

answered Oct 16 '12 at 01:59

Lightness Races in Orbit

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yup.. nothrow is working.. but why visual stuio is creating a name.lib file in release folder. Is there any effect of this lip file when we build a setup MSI file. ? – maxpayne Oct 16 '12 at 02:12
@furqan: That is a completely unrelated question. – Lightness Races in Orbit Oct 16 '12 at 03:20

score 0 · Answer 3 · answered Oct 16 '12 at 01:55

0

C++ "new" does not return null on failure, it calls the new handler.

answered Oct 16 '12 at 01:55

Permaquid

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Allocation of large amount of memory gives error ? Why?

3 Answers3