Bug 5023 – Docs about order of execution of invariant and pre/post conditions
Status
RESOLVED
Resolution
FIXED
Severity
normal
Priority
P2
Component
dlang.org
Product
D
Version
D2
Platform
All
OS
All
Creation time
2010-10-09T06:35:00Z
Last change time
2012-01-19T13:58:09Z
Keywords
spec
Assigned to
nobody
Creator
bearophile_hugs
Comments
Comment #0 by bearophile_hugs — 2010-10-09T06:35:21Z
This D2 docs page states:
http://www.digitalmars.com/d/2.0/class.html#invariants
> The invariant is checked when a class constructor completes, at the start of
> the class destructor, before a public or exported member is run, and after a
> public or exported function finishes.
If preconditions, postconditions and invariants are pure functions then they need to refuse the usage of functions like printf() inside them. If they aren't pure (maybe because they must support printing and logging), then printing and logging is a side effect, and their order of execution counts.
Even if preconditions, postconditions and invariants are pure functions, their purpose is to stop the execution of the program when there's a bug, so during debugging it's important to know the order of execuction of those contracts, to understand where the bug is.
Either way, the order of execution of preconditions, postconditions and invariants is important and it needs to be stated in the D documentation (and it needs to be the same in different D implementations).
So I suggest to change the D docs like this:
> The invariant is checked when a class constructor completes, at the start of
> the class destructor, before a public or exported member is run (before its precondition),
> and after a public or exported function finishes (after its postcondition).
Comment #1 by bearophile_hugs — 2010-10-09T06:36:54Z
See bug 5024
Comment #2 by bugzilla — 2012-01-19T13:57:27Z
Fixed, but the order is preconditions, invariant, body, invariant, postconditions.
Comment #3 by bugzilla — 2012-01-19T13:58:09Z
*** Issue 5024 has been marked as a duplicate of this issue. ***