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From: gwyn@BRL.ARPA (VLD/VMB)
Newsgroups: net.lang.c
Subject: Re:  Global ptrs init to NULL or 0000?
Message-ID: <3239@brl-tgr.ARPA>
Date: Fri, 15-Nov-85 01:43:03 EST
Article-I.D.: brl-tgr.3239
Posted: Fri Nov 15 01:43:03 1985
Date-Received: Sat, 16-Nov-85 09:49:09 EST
Sender: news@brl-tgr.ARPA
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I don't see much problem with the requirement that any defined
statically-allocated storage that has no explicit initializer
be initialized as though the constant 0 were assigned to it.
(This phrasing ensures that such pointers will start out with
the correct representation for null pointers (not necessarily
a zero bit pattern)).

As I am sure you are aware, a vast quantity of existing C code
assumes that such data is implicitly initialized to "zero"
(not necessarily with the same interpretation as X3J11), so
your example of
	int	big_array[32767];
would have to be initialized to zero somehow in any reasonable
existing implementation of C.  The UNIX .bss trick works only
for a limited set of architectures anyhow; if "zero" means a
non-zero bit pattern, the compiler or linker is going to have
to use an approach other than auto-zeroing of .bss upon
process startup.

I believe your point was that there may be overhead caused by
this initialization, even in the case that the
auto-init-to-zero values are not going to be used because the
code is going to store into the array before referencing it.

I agree that it would be much cleaner to declare that defined
data that is not explicitly initialized may not be referenced
until after something has been explicitly stored into it.  I
follow this practice in my own code (not counting modifications
to existing software that does not follow these rules).  But
that would clearly "invalidate" much existing code that has
(reasonably) been considered correct up to now.