Re: Minimizing Dynamic Memory Allocation
* James Kanze:
On Jan 27, 11:29 am, "Alf P. Steinbach" <al...@start.no> wrote:
* James Kanze:
[snip]
To avoid leaks, all classes should include a destructor
that releases any memory allocated by the class'
constructor.
This is just dumb advice.
And it contradicts the advice immediately above: "have a
clear understanding of resource acquisition".
Use types that manage their own memory.
Which is exactly what the "advice" you just called dumb said.
Nope.
The "advice" in the proposed guidelines was to define a
destructor in every class.
Where did you see that?
Top of this quoted section. :-)
The quoted section doesn't say that the user has to define a
destructor. It says that the class must "include a destructor
[user defined or implicit] that releases any memory allocated by
the class' constructor." In other words, the class author
should ensure that any memory allocated by the classes
constructor is released in the destructor---there's nothing
there about having to do so explicitly, just ensuring that it is
done.
As I see it your interpretation of the wording is meaningless, but we'll
probably not agree on that, so...
[snip]
The biggest problem with trying to catch bad_alloc is that some
systems undermine it. Linux, for example, unless you configure
it specially. Maybe Windows as well; the one time I
experimented with it under Windows (but that was Windows NT with
VC++ 6.0---a long time ago), rather that getting bad_alloc, the
system suspended my process and brought up a pop-up window
suggesting that I terminate other processes. Not a very useful
reaction for a server, where there's no one in front of the
screen, and the connection will time out if I don't respond in a
limited time.
The reasonable approach for allocating a large chunk of memory for e.g. a
document or for a sub-allocator would IMHO be to use new(std::nothrow), because
the possibility of allocation failure is then part of the normal case outcome.
For Windows one would probably have to call SetErrorMode at app startup.
The documentation doesn't mention whether it affects out-of-memory handling but
the documentation is in general incomplete, and it's not unlikely.
Cheers & hth.,
- Alf