Re: SGCL - Garbage Collector for C++

James Kanze <>
Tue, 4 Mar 2008 04:43:56 -0800 (PST)
On Mar 3, 6:27 am, Kai-Uwe Bux <> wrote:

Sam wrote:

James Kanze writes:




collection is essential in Java, because all objects must be
allocated dynamically, and user defined types can't have value
semantics. It's optional in C++, because we do have value
semantics. Optional, but it still saves the programmer some
unnecessary work.

No, it's not "optional" in C++. It does not exist, at all,
in C++. Go look up the "optional" part of ISO/IEC 14882:2003
that defines whatever you think "garbage collection" means
in the C++ context. I eagerly await the results of your

I don't think that is entirely correct.

It's not correct at all. However...

The C++ standard is worded very cautiously with regard to new
and delete to leave a tremendous amount of freedom to the
implementation. I think, a compliant implementation could use
garbage collection. In particular, I do not know of any
language in the C++ standard that would require the following
program to ask the execution environment for an unbounded
amount of memory:

  int main ( void ) {
    while ( true ) {
      new int ( 5 );

There are a few legal constructs in C++ which do cause problems
with garbage collection. (They don't occur in any reasonable
real programs, but they are formally there.) When I said it was
"optional", I was thinking in terms of the way threading is
optional. The standard doesn't really define it, and you do
need to fudge a few things to make it fit, but in practice, it's
available to anyone that wants it, and it's actually widely used
in C++ applications already. Just like threading.

James Kanze (GABI Software)
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