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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: GNAT bugs around use of "for X'Address..." clause
Date: Fri, 22 May 2015 08:38:35 +0100
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Date: 2015-05-22T08:38:35+01:00
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erik.shadwick@gmail.com writes:

> Should I be submitting this to AdaCore, or GCC's
> http://gcc.gnu.org/bugs.html bug tracker? When running this with my
> copy of GNAT free/GPL, it suggests the former, but when compiling it
> through ideone.com I get the message to put it into GCC's tracker. It
> detects the error in "in gnat_to_gnu_entity, at
> ada/gcc-interface/decl.c:347".

FSF GCC 4.9.1 raises a bug box (in a different place).
5.1.0 doesn't crash, but says (as I expected)

warning: default initialization of "X" may modify overlaid storage
warning: use pragma Import for "X" to suppress initialization (RM B.1(24))

(that is, "X : P.Checked_T with Import, Convention => Ada;")

Unfortunately, fixing that doesn't make your problem go away.

You could wait for GNAT GPL 2015, or you could try the FSF 5.1.0 at [1].

> Further, what is the validity of assigning to a variable that has the
> 'Address clause on it -- is it legal and defined behaviour?

Yes, but writing to System.Null_Address will probably not produce useful
behaviour. What you have here is an interaction between the type
invariant and the address setting.

[1] https://sourceforge.net/projects/gnuada/files/GNAT_GCC%20Mac%20OS%20X/5.1.0/