Rooters,
I was just wondering what the 'official' position was on running
without libNew. Is this mode officially supported? Since they are
separate libraries, it is obviously very easy to omit libNew and either
use the default system on or put in your own.
The reason I ask this is that the way libNew works makes it very easy
to write wrong code which will fail drastically without it. LibNew
initializes all of the memory space allocated inside it to 0; and that
means that people assume that pointer (and other) members in a TObject
default to 0 (laying aside the issue of the rare compiler that does not
use all-bits-0 for the null pointer). They do not, of course, in
ordinary C++ code; they are left unintialized, meaning random garbage,
unless you initialize them. This is true even on the stack, of course,
but since the ROOT idiom seems to be strongly slanted towards heap
allocation*, many users never see the errors that could crop up from
failure to correctly initialize on the stack.
Now, I am trying to run root and our local root-derived libraries under
Insure++, a leak/memory misuse detection system that doesn't interact
very well with libNew (and takes on libNew's functionality and more, so
there's no point in keeping it around). But because libNew's convenient
zeroing of members is now gone, I get to deal with all the
non-initialized problems which people should have seen long ago and
fixed, even before getting to use the tool to find the real problems
I'm looking for.
Since the global operator new doesn't get called for static allocation,
this also provides a very nasty surprise for people who think that code
has been well-tested -- until someone tries to use one of their object
on the stack.
So I guess I am suggesting that the zero-ing out provided in libNew is
more of a curse than a blessing, in the long run, and ought to be
removed in favor of making (er, helping to encourage) people write
their constructors correctly the first time.
George Heintzelman
gah@bnl.gov
*It's so strongly slanted that I've seen people (who have never seen
C++ outside of Root) write code like this, I kid you not. Don't even
ask about using contained data members instead of pointers:
void function() {
TSomeObject *x = new TSomeObject();
// Do some processing
// ..
// ..
delete x;
}
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