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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Mon, 7 Feb 2011 01:00:22 -0800 (PST)
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Date: 2011-02-07T01:00:22-08:00
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Dmitry A. Kazakov wrote:
> Immutable scalar arguments still ire mutable within C and C++ subprograms.
> Great ideas never die...

Agreed.  I recently found another bug in a C program that was caused
by changing the value of a "passed-by-copy" parameter.  Of course the
caller was unaffected but the algorithm inside the function was
broken.

In Ada, if you write:

procedure Foo (Arg : in Integer) is
begin
   Arg := 3;
end Foo;

you get a compile-time error.

void foo (int arg) { arg = 3; }

then it "works".  In the case I'm talking about, the assignment broke
an invariant inside the function, such that the function had bad side-
effects.

--
Ludovic Brenta.