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digitalmars.D.bugs - [Issue 796] New: Error: AssertError Failure internal\invariant.d(14)

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=796

           Summary: Error: AssertError Failure internal\invariant.d(14)
           Product: D
           Version: 1.00
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: lio lunesu.com


The following code causes a run-time assertion failure in
internal\invariant.d(14) when linked against a debug build of Phobos (-unittest
-g -w):

#class Class {}
#void main(){
#    Class c;
#    assert(c);
#}

It causes a run-time Access Violation when linked against the release build of
Phobos.


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Jan 05 2007
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=796


fvbommel wxs.nl changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |spec




------- Comment #1 from fvbommel wxs.nl  2007-01-05 08:48 -------
It seems to be according to the spec though.
I just looked it up, and assert(object) checks object's invariant; not just
that it isn't null (that's assert(object !is null) apparently).
Not what I would've expected...
This isn't exactly clearly noted: this is mentioned on
http://www.digitalmars.com/d/class.html#invariants but not
http://www.digitalmars.com/d/expression.html#AssertExpression where it would be
expected (especially since you wouldn't normally look at the section on
invariants when figuring out what an assert does).
So maybe this should be noted there too (especially since every other use of
objects in boolean context is a null check AFAIK). I've already added it to the
comments page for that page.

The invariant checking routine in the runtime does perform an assert(o !is
null), but that only gets compiled into a non-release build of Phobos.
In a release build it instead segfaults trying to look up the vtable of the
object. (to get classinfo)


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------- Comment #2 from lio lunesu.com  2007-01-06 02:54 -------
Nice catch! I never would have thought of that.

In any case, the assertion failure / access violation can be easily fixed if
the compiler where to add a null-pointer check prior to checking the
invariants. Frankly, I think this makes sense too. We can expect many C/C++
people doing "assert(instance)" only to check the pointer. If it were to check
both the pointer and the invariants, that would just make it even more useful.

AFAIK, this cannot be changed by adding a check to invariant.d, since that
would add unnecessary overhead to all invariant checks. The code generation for
assert(instance) should be changed to include a pointer check: the assertion
should fail for null-pointers:

assert(classref) 
// =>
assert( (classref !is null) && _d_invariant(classref) );


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Jan 06 2007
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fvbommel wxs.nl changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|spec                        |wrong-code




------- Comment #3 from fvbommel wxs.nl  2007-01-11 04:13 -------
It seems I misread the spec: it says the invariant *can* be checked on
assert(classref), not that it *will* be. So the spec's fine.
The bug seems to be in the compiler.


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Jan 11 2007
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smjg iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smjg iname.com
           Keywords|                            |diagnostic
            Summary|Error: AssertError Failure  |Asserting a null object
                   |internal\invariant.d(14)    |reference throws AssertError
                   |                            |Failure
                   |                            |internal\invariant.d(14) or
                   |                            |Access Violation




------- Comment #4 from smjg iname.com  2007-01-11 09:04 -------
Indeed,

    assert(classref)

should be translated inline to

    assert((classref !is null) && _d_invariant(classref));

so that the error location is preserved.


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Jan 11 2007
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------- Comment #5 from torhu yahoo.com  2007-04-12 18:55 -------
I think the assert feature would be more intuitive if assert(obj) would only
check for a null reference.  That's what people expect it to do, and that's
what they use it for most of the time.  But doing both kinds of checks would be
better than the current behavior.

If you really wanted to check the invariant explicitly, the syntax could be
'obj.invariant', 'invariant(obj)' or similar.  This could be useful in the
class' own methods, where there's no need to check for a null reference anyway.


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Apr 12 2007
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Andrei Alexandrescu <andrei metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |andrei metalanguage.com
         AssignedTo|nobody puremagic.com        |bugzilla digitalmars.com


--- Comment #6 from Andrei Alexandrescu <andrei metalanguage.com> 2010-11-26
14:13:26 PST ---
Still present in 2.050.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Bernard Helyer <blood.of.life gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |blood.of.life gmail.com


--- Comment #7 from Bernard Helyer <blood.of.life gmail.com> 2011-03-07
03:12:41 PST ---
Every time I write 

  assert(object);

A dagger pierces my heart and I remember I must write

  assert(object !is null); 

Could we get this fixed this decade some time?

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--- Comment #8 from Stewart Gordon <smjg iname.com> 2011-03-07 04:17:53 PST ---
(In reply to comment #7)
 Every time I write 
 
   assert(object);
 
 A dagger pierces my heart and I remember I must write
 
   assert(object !is null); 
 
 Could we get this fixed this decade some time?

Indeed. The intended behaviour (check that object is non-null AND satisfies its invariants) needs to be built into the compiler, not delegated to the RTL. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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Mike Shulman <viritrilbia+d gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |viritrilbia+d gmail.com


--- Comment #9 from Mike Shulman <viritrilbia+d gmail.com> 2011-05-31 13:45:01
PDT ---
FYI: As a new D programmer, I found the segfault produced by this sort of code
very confusing, and spent almost an hour trying to figure out where the issue
in my code was and why I wasn't just getting an AssertError.  Only when I found
this bug report did I have any idea what was going on.

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