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digitalmars.D.bugs - [Issue 3194] New: invariant should be checked at the beginning and end of protected functions

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3194

           Summary: invariant should be checked at the beginning and end
                    of protected functions
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: andrei metalanguage.com


Consider:

class A
{
    invariant() { ... }
    public void f() { ... }
    protected void g() { ... }
}

Currently invariant is called at the beginning and end of each public function,
the end of the constructor, and the beginning of the destructor. Scott Meyers
pointed out to a quite known fact - protected is much closer to public than to
private in terms of offering access control. This is because anyone can just
inherit from a class and call protected methods, or even wrap them in public
methods.

Consequently, it looks like the invariant of a class must also hold upon entry
and exit of all protected methods.

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Jul 20 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3194


yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
                 CC|                            |yebblies gmail.com



Patch for D2
https://github.com/D-Programming-Language/dmd/pull/112

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Jun 11 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3194


Diego Canuhe <canuhedc gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |canuhedc gmail.com



---


 Patch for D2
 https://github.com/D-Programming-Language/dmd/pull/112


I disagree.
Even while you can easily access protected methods of a class, they are
intended for internal use, otherwise they'd be public.

Consider:

class A
{
    abstract protected SomeType[] getData();

    public void processData()
    {
        //do something that breaks the invariants
        foreach (SomeType element; getData())
        {
            //do something...
        }
        //do something that restores the invariants
    }

    invariant() {...}
}

a class B derived from A implementing getData() shouldn't have to respect the
invariants while entering/leaving getData(). Anything regarding getData()'s
side-effects should be put in an out clause.

BTW, abstract functions shouldn't require a body clause accompanying in and out
clauses

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Jun 22 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3194


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED



12:54:14 PDT ---
https://github.com/D-Programming-Language/dmd/commit/95c4a647d224962e6323cecf5ddff961ac38da99

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Oct 09 2011