Re: GNAT bug with assertions

[Simon Wright <simon@pushface.org>]

Jacob Sparre Andersen <jacob@jacob-sparre.dk> writes:

> AdaMagica wrote:
>
>> I would have expected that predicates are also checked on return
>> values as they are checked on parameters.  In the following test, no
>> exception is raised on call of funcction Wrong although it returns a
>> value not fulfilling the predicate.
>>
>> Is this a GNAT bug or my wrong expectation?
>
> It seems that your expectations are slightly off.

Or perhaps you, Jacob, have a later release of the compiler which has
this bug fixed?

> Contracts are only checked if the assertion policy is set to "Check".
> You can do that, either by configuring your compiler to have the
> assertion policy set to "Check", or by explicitly inserting:
>
>    pragma Assertion_Policy (Check);
>
> at the beginning of the units, which should have this assertion policy.

Or, in the case of GNAT, by giving -gnata: see
http://docs.adacore.com/gnat_ugn-docs/html/gnat_ugn/gnat_ugn/building_executable_programs_with_gnat.html#debugging-and-assertion-control

If Cristoph hadn't been using -gnata, the first check would have failed.

IMO this is a bug in GNAT, present in CE2018 and FSF GCC 8 (and maybe
earlier, didn't check).