Re: Silver bullet for C++ memory management ?

From: (Stefan Ram)
Sat, 28 Mar 2009 20:17:23 CST
peter koch <> writes:

On 26 Mar., 02:49, (...) Stefan Ram wrote:

In Java, one can not have objects on the stack,

   In C++, one also can not have objects on the ?stack? (ISO/IEC
   14882:2003(E) does not mention a ?stack? in this sense). Of
   course, a stack is a feature of many C++ /implementations/
   (not of the language [except for the class template

   On the other hand, I now remember, that some Java
   implementations have or a going to have ?escape analysis? for
   the lifetime of an object: If the implementation can prove
   that the object's lifetime will not escape a method
   incarnation, it then /will/ be placed on the stack (into this
   method's stack frame) - also an implementation feature.

   So in Java one /can/ have objects on the stack in a similar
   sense as in C++ (in C++, one possibly can have more objects on
   the stack).

The above is a clear indication that one of two conditions were
a) The code was not critical, so the programmers did not care about
b) The programmers was incompetent.

   There are shades of gray between ?competent? and

   Were the programmers and managers involved in the Mars Climate
   Orbiter loss due to a mixture of pounds and kilograms in 1999

   There are languages, where less competent programmers will
   more often get more correct results. Where they cannot make
   certain mistakes and have to do less bookkeeping, which frees
   mental resources for other realms.

In practice, Java will be 2-3 times slower than the same
program written in C++ or a comparable language - e.g. Ada.

   I believe, in the average, this should be approximately true.

And yet Java imposes a OO paradigm.

   Java is neither fully nor purely object-oriented, but, yes,
   it supports run-time polymorphism, but not the template
   instantiation at compile time as in C++.

   (But some Java implementations have just-in-time compilation,
   which partially can make up for this, although this is
   does not address the same abstractions/instantiations.)

Memory management has never been a major problem.

   When one is starting to build a graph to keep track of
   relations and nodes, and parts of the graph can be deleted
   from this graph at run-time, one needs to check whether after
   a removal of a part of the graph there are new disconnected
   (unreachable parts) of the graph; they, too, need to be
   disposed, then. To find them, one needs to implement some kind
   of garbage collector, if the programming language does not
   already have one.

   In other cases, one might get by with certain rules about
   memory ownership and its transfer.

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