Re: Representing data differently

[Craig Carey <research@ijs.co.nz>]

On 10 Feb 2003 12:47:23 GMT, Colin_Paul_Gloster@ACM.org (Colin Paul
Gloster) wrote:
...
>     for X'Address use Y'Address;
>     pragma Import (Y);
>           --  :Stops default initialising of pointers (not in GNAT 3.14)
...
>Why is the convention missing from this import statement?


That is quoted text, and the quote could have been corrected. Thus I
object to the use of the present tense in the question. It does not seem
to be an interesting question. The solution I showed is not very nice,
with how the "-gnatR" option to show byte offsets might be done, with
an a one or more edits and compiles until Ada union struct type is
defined properly.

The rule on no default initializations is defined with this text:

Ada Reference Manual : B.1 Interfacing Pragmas

38.  Notwithstanding what this International Standard says elsewhere,
the elaboration of a declaration denoted by the local_name of a pragma
Import does not create the entity. Such an elaboration has no other
effect than to allow the defining name to denote the external entity.

38.a.  Ramification: This implies that default initializations are
skipped. (Explicit initializations are illegal.) For example, an
imported access object is not initialized to null.

  http://www.adaic.org/standards/95aarm/html/AA-B-1.html