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Article View: comp.std.c
Article #4513

Re: Alignment of malloc()

#4513
From: Arno Eigenwillig
Date: Sat, 30 Dec 1995 01:14
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In article <DKDA7D.Kw7@midway.uchicago.edu>, Michael Spertu writes:

> The standard says that the return value of malloc() should be properly
> aligned for all data type. On the one hand, code that uses floats will
> endure gross performance penalties if it doesn't check alignment, and
> programmers shouldn't have to align all their malloc()s. On the other
> hand, the code still runs, albeit inefficiently.

That is a quality-of-implementation issue and hence beyond the scope
of The Standard. All The Standard defines in the end is the output a C
program creates, not the timing nor (thanks to the as-if rule) the way
it creates it.

It should be relatively easy to write your own malloc() wrapper,
though, that calls malloc() for a slightly [1] larger block and
returns a better aligned pointer to within that block.

_______
[1] new_blocksize - old_blocksize, that is

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Path: arc1-ca.pugleaf.net!phoenix.rhein.de!yaps!arno
From: arno@yaps.rhein.de (Arno Eigenwillig)
Newsgroups: comp.std.c
Subject: Re: Alignment of malloc()
Message-ID: <j66Sx*FRe@yaps.rhein.de>
Date: Sat, 30 Dec 1995 02:14:43 +0100
References: <DKDA7D.Kw7@midway.uchicago.edu>
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