Re: std::map element in heap or stack?

From:

Kaz Kylheku <kkylheku@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 29 Dec 2009 23:25:52 +0000 (UTC)

Message-ID:

<20091229151502.485@gmail.com>

On 2009-12-26, Michael Tsang <miklcct@gmail.com> wrote:

shuisheng wrote:

Dear All,

I am wondering the inserted element in std::map is located in heap or
stack? For example

std::map<int, double> a;
a[0] = 3.14;

The element of the map: pair<int, double>(0, 3.14) is in heap or
stack? I think to know it is important for memory management.

Thank you a lot ahead,

Shuisheng

The C++ standard does not actually define the terms "heap" and "stack". The
only part which the standard uses "stack" is "stack unwinding", which is
related to exception handling.

The C++ standard doesn't define every technical term that it uses. however,
it includes a technical glossary via a normative reference to this
document:

ISO/IEC 2382 (all parts), Information technology---Vocabulary

which makes that document (all parts of it, evidently) part of the C++
standard.

If you do not have that document, then you effectively do not have the complete
C++ standard; you don't know whether or not the C++ standard defines the term
"stack".

If the C++ standard doesn't define that term, then its use in the description
of exception handling is a defect.

It would be astonishing if the definition of stack (if it exists) were at odds
with what nearly every computer scientist understands as a minimal definition
of a stack: namely that it is a data structure whose principal operations
provide a LIFO storage and access discipline.

Local variable storage in C++ demonstrates the LIFO property, therefore
it is probably acceptable to to refer to it as a stack, barring an unusual
or missing definition in ISO 2382.

``Heap'' isn't used in the standard, but it's a widely understood term which
refers to exactly the same kind of abstraction as ``free store'' in C++ or
``dynamic storage'' in C. In that context, it doesn't describe any particular
structure (contrast with ``binomial heap'' which is something else). It doesn't
pose any obstruction to meaningful or correct dialog.

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