bad_alloc in new

Hello everyone,


I usually check whether there is bad_alloc thrown to identify whether the allocation is success or not.

My question is,

Is there a way to disable bad_alloc and just to check the returned pointer NULL or not to identify allocation success or not -- which from function point of view, is as correct as the way to catch bad_alloc? Windows platform/Visual Studio is ok. I always see code does not check bad_alloc and just check the return pointer.

(My solution is to select Enable C++ Exception to No in Code Generation option in Visual Studio, not sure whether it is the most correct way.)


thanks in advance,
George

To have new return a null pointer, instead of throwing an exception use nothow new.

Code:

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#include <new>
...
int *maybe_null = new(std::nothrow) int;

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In general it is best to use regular new, because in most cases there in nothing that a function can do about bad_alloc. Thus the exception would get propagated to something that can handle the problem, or if there isn't anything, quit.

You intended std::nothrow, I assume, King Mir.

Yep, good catch.

Thanks King,


No need to link with nothrownew.obj?

Quote:

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Originally Posted by King Mir

To have new return a null pointer, instead of throwing an exception use nothow new.

Code:

---

#include <new>
...
int *maybe_null = new(std::nothrow) int;

---

In general it is best to use regular new, because in most cases there in nothing that a function can do about bad_alloc. Thus the exception would get propagated to something that can handle the problem, or if there isn't anything, quit.

---

regards,
George

<new> is part of the c++ standard library. So as long as you link to that, you're all set.

No, that's a backward compatibility solution of MS.

What King Mir showed is the standard way.

Out of curiosity, what do you do when you've caught a bad_alloc?

Hi King,


Looks like we need to link with nothrownew.obj

http://msdn2.microsoft.com/en-us/library/kftdy56f.aspx

Quote:

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Originally Posted by King Mir

<new> is part of the c++ standard library. So as long as you link to that, you're all set.

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regards,
George

No, you don't. Use nothrow new. Don't make the normal new not throw with a stupid compiler workaround.

Thanks CornedBee,


No need to link with nothrownew.obj? I have posted information in #8 of this thread, looks like MSDN is confusing. :-)

Quote:

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Originally Posted by CornedBee

No, that's a backward compatibility solution of MS.

What King Mir showed is the standard way.

Out of curiosity, what do you do when you've caught a bad_alloc?

---

regards,
George

Thanks CornedBee,

1.

The walkaround you mean link with nothrownew.obj?

2.

I want to confirm with you from my understanding that,

I. using std::nothrow is using nothrow new (not normal new);
II. linking with nothrownew.obj replaces the normal new?

Quote:

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Originally Posted by CornedBee

No, you don't. Use nothrow new. Don't make the normal new not throw with a stupid compiler workaround.

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regards,
George

Quote:

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Originally Posted by George2

1. The walkaround you mean link with nothrownew.obj?

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Yes!

Quote:

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I. using std::nothrow is using nothrow new (not normal new);

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Yes!

Quote:

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II. linking with nothrownew.obj replaces the normal new?

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Yes! Hence, workaround.

George,

1) Yes, CornedBee's meant that "nothrownew.obj" is a compiler/vendor specific workaround. It also happens to be unnecessary, as the standard supports a non-throwing form of new.

2 I) "new (std::nothrow) whatever" is what CornedBee was referring to as the "nothrow new". It is specified in the C++ standard.

2 II) linking with nothrownew.obj replaces the "normal new"; it links in, in a compiler specific manner, an implementation of the non-placement operator new that behaves in a non-standard manner.

Thanks Elysia and grumpy!


Your help is great! My question is answered.

Quote:

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Originally Posted by grumpy

George,

1) Yes, CornedBee's meant that "nothrownew.obj" is a compiler/vendor specific workaround. It also happens to be unnecessary, as the standard supports a non-throwing form of new.

2 I) "new (std::nothrow) whatever" is what CornedBee was referring to as the "nothrow new". It is specified in the C++ standard.

2 II) linking with nothrownew.obj replaces the "normal new"; it links in, in a compiler specific manner, an implementation of the non-placement operator new that behaves in a non-standard manner.

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regards,
George

And if there's any part of the program that relies on new throwing, linking against nothrownew.obj will break this part. Which is why it's a stupid thing to do. You use this workaround only for programs written before new threw.

Thanks CornedBee,


Great point!

Quote:

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Originally Posted by CornedBee

And if there's any part of the program that relies on new throwing, linking against nothrownew.obj will break this part. Which is why it's a stupid thing to do. You use this workaround only for programs written before new threw.

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regards,
George