Re: Valid Attribute and Unchecked Conversion

[kst@thomsoft.com (Keith Thompson)]

In <dewar.844516953@schonberg> dewar@schonberg.cs.nyu.edu (Robert Dewar) writes:
[...]
> Indeed the Ada 95 section on unchecked conversion (section 13.9) does not
> mention the word erroneous at all, so an unchecked conversoin BY ITS SELF
> never makes a program execution erroneous in Ada 95.

But RM95-13.9.1(12) says:
	A call to an imported function or an instance of
	Unchecked_Conversion is erroneous if the result
	is scalar, and the result object has an invalid
	representation.

Probably that paragraph should have been in 13.9 rather than 13.9.1.

Note that there are several paragraphs after this in the AARM encouraging
implementations to behave sensibly:

	[...] We considered requiring such sensible behavior,
	but it resulted in too much arcane verbiage, and
	since implementations have little incentive to behave
	irrationally, such verbiage is not important to have.

So implementations are encouraged to implement sensibly something that
users are encouraged to avoid.

-- 
Keith Thompson (The_Other_Keith) kst@thomsoft.com <*>
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