Re: Allocations that overflow

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Thu, 19 Jun 2008 15:00:19 -0400
Message-ID:
<uQoi56j0IHA.2408@TK2MSFTNGP04.phx.gbl>
Angel Tsankov <fn42551@fmi.uni-sofia.bg> wrote:

According to the standard, what must the following function do if it
is passed std::numeric_limits<std::size_t>::max()?

struct S
{
char a[64]; // Any size greater than 1 would do.
};

S* allocate(std::size_t size)
{
return new S[size];
}


It can do anything, or not be run at all. It goes like this:

5.3./1 The new-expression attempts to create an object...

Annex B
1 Because computers are finite, C++ implementations are inevitably
limited in the size of the programs they can successfully process...
2 The limits may constrain quantities that include those described below
or others...
- Size of an object

1.4/2 ... If a program contains no violations of the rules in this
International Standard, a conforming implementation shall, *within its
resource limits*, accept and correctly execute that program (emphasis
mine).

The implication is that if the program exceeds implementation resource
limits, it may be rejected or executed incorrectly.

But see:

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#256
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#624

It seems likely that the next version of the standard would require
bad_alloc exception in this situation.
--
With best wishes,
    Igor Tandetnik

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