From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: [OT] About const int
Date:	18 Jul 2001 17:14:50 GMT
Organization:	Aachen University of Technology (RWTH)
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References:	<5BF60CD649EDD411A04600B0D049F53AFFA913 AT hydmail02 DOT hyd DOT wilco-int DOT com>
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Prashant Ramachandra <rprash AT wilco-int DOT com> wrote:
> I have a question that's probably got nothing to with DJGPP, so please
> forgive me for this off-topic post.

> I tried the program below and interestingly, it gives me...

> "Constant is 10. It is actually 1"

That program is very incorrect. It causes undefined behaviour at the
point of the cast from (const int *) to (int *). Gcc would have warned
you about this, if only you had asked for assistance (rule of thumb:
always use '-Wall' unless you have very good reasons not to).

> Shouldn't gcc not make the assumption that the value of j *is* 10 and
> instead reference itfrom memory instead.

No, it shouldn't. You'll have to make up your mind: either j *is*
constant, or it isn't. You can't have it both ways.

If you lie to the compiler like in this piece of source code, _you_
take responsibility for all consequences.
-- 
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

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