Re: History of - if(p) delete p; - ... ?

From:

Ulrich Eckhardt <eckhardt@satorlaser.com>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 26 Jan 2009 17:12:47 +0100

Message-ID:

<v04156-fcp.ln1@satorlaser.homedns.org>

Martin T. wrote:

[...] our code base uses the following construct basically all the time:
int* p = ...
if(p)
free(p); // or delete, or delete[]
p = NULL;

I think the code was initially created on Visual Studio 4 and then got
ported over the years to 5/6/now 2005 ...
I'm trying to figure out why we always used this construct even though
it's not necessary.
Was it *ever* necessary? Pre VC6, pre VC5, ... ?? Has the free function
in C always been specified as noop in case of NULL ?

The behaviour of 'delete' with a null pointer is well defined for quite some
time. What I wouldn't bet on is the quality of implementations. However,
even VC6, which is ten years old, gets this right, so I think you can
assume that it works. I'm not sure about free(NULL) though, but I think C89
(i.e. 20 years ago!) already required it to be a no-op. If you want to port
to ancient platforms, that could be an issue, otherwise I just wouldn't
bother and treat those checks as noise.

Uli

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