http://d.puremagic.com/issues/show_bug.cgi?id=2328

           Summary: setTypeInfo in gc.d backwards.
           Product: D
           Version: 2.018
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P2
         Component: Phobos
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: dsimcha@yahoo.com


According to Phobos object docs:

uint flags();
    Get flags for type: 1 means GC should scan for pointers

This is implemented correctly.

import std.stdio;

void main() {
    writefln(typeid(uint).flags & 1);  //0
    writefln(typeid(uint*).flags & 1); //1
    writefln(typeid(void*).flags & 1); //1
    writefln(typeid(float).flags & 1); //0
}

However, source code to setTypeInfo:

void setTypeInfo(TypeInfo ti, void* p)
{
    if (ti.flags() & 1)
        hasNoPointers(p);
    else
        hasPointers(p);
}

The if statement in this code is clearly backwards.


-- 

d-bugmail@puremagic.com wrote:
> http://d.puremagic.com/issues/show_bug.cgi?id=2328
> 
>            Summary: setTypeInfo in gc.d backwards.
>            Product: D
>            Version: 2.018
>           Platform: All
>         OS/Version: All
>             Status: NEW
>           Severity: major
>           Priority: P2
>          Component: Phobos
>         AssignedTo: bugzilla@digitalmars.com
>         ReportedBy: dsimcha@yahoo.com
> 
> 
> According to Phobos object docs:
> 
> uint flags();
>     Get flags for type: 1 means GC should scan for pointers 
> 
> This is implemented correctly.
> 
> import std.stdio;
> 
> void main() {
>     writefln(typeid(uint).flags & 1);  //0
>     writefln(typeid(uint*).flags & 1); //1
>     writefln(typeid(void*).flags & 1); //1
>     writefln(typeid(float).flags & 1); //0
> }
> 
> However, source code to setTypeInfo:
> 
> void setTypeInfo(TypeInfo ti, void* p)
> {
>     if (ti.flags() & 1)
>         hasNoPointers(p);
>     else
>         hasPointers(p);
> }
> 
> The if statement in this code is clearly backwards.

I'm fairly certain that the doc comment is simply wrong.  Last time I checked, the flag was 1 for "has no pointers" as per the implementation.  I'd actually prefer it to work as the comment suggests, however.

== Quote from Sean Kelly (sean@invisibleduck.org)'s article
> d-bugmail@puremagic.com wrote:
> > http://d.puremagic.com/issues/show_bug.cgi?id=2328
> >
> >            Summary: setTypeInfo in gc.d backwards.
> >            Product: D
> >            Version: 2.018
> >           Platform: All
> >         OS/Version: All
> >             Status: NEW
> >           Severity: major
> >           Priority: P2
> >          Component: Phobos
> >         AssignedTo: bugzilla@digitalmars.com
> >         ReportedBy: dsimcha@yahoo.com
> >
> >
> > According to Phobos object docs:
> >
> > uint flags();
> >     Get flags for type: 1 means GC should scan for pointers
> >
> > This is implemented correctly.
> >
> > import std.stdio;
> >
> > void main() {
> >     writefln(typeid(uint).flags & 1);  //0
> >     writefln(typeid(uint*).flags & 1); //1
> >     writefln(typeid(void*).flags & 1); //1
> >     writefln(typeid(float).flags & 1); //0
> > }
> >
> > However, source code to setTypeInfo:
> >
> > void setTypeInfo(TypeInfo ti, void* p)
> > {
> >     if (ti.flags() & 1)
> >         hasNoPointers(p);
> >     else
> >         hasPointers(p);
> > }
> >
> > The if statement in this code is clearly backwards.
> I'm fairly certain that the doc comment is simply wrong.  Last time I
> checked, the flag was 1 for "has no pointers" as per the implementation.
>   I'd actually prefer it to work as the comment suggests, however.

Nope, I actually tested the implementation.  I didn't just assume the doc comment was right.  Furthermore, I tried to write code based on the expected behavior of Phobos's setTypeInfo() and it was clearly broken.  Lying to setTypeInfo() about the type fixed it.  Note that I don't know if this bug exists in Tango or Phobos/D1, only that it does exist in Phobos/D2.

dsimcha wrote:
>>>
>>> The if statement in this code is clearly backwards.
>> I'm fairly certain that the doc comment is simply wrong.  Last time I
>> checked, the flag was 1 for "has no pointers" as per the implementation.
>>   I'd actually prefer it to work as the comment suggests, however.
> 
> Nope, I actually tested the implementation.  I didn't just assume the doc comment
> was right.  Furthermore, I tried to write code based on the expected behavior of
> Phobos's setTypeInfo() and it was clearly broken.  Lying to setTypeInfo() about
> the type fixed it.  Note that I don't know if this bug exists in Tango or
> Phobos/D1, only that it does exist in Phobos/D2.

Oops, I was thinking of ClassInfo, which uses "&2" to represent "hasNoPointers."  You're right that TypeInfo uses "&1" to represent "hasPointers."  A bit confusing, so it doesn't surprise me that setTypeInfo is wrong.  However, Phobos' use of this flag in the runtime code is actually correct.  See internal/gc/gc.d, for example.  In short, setTypeInfo should probably just be deleted, since it's both incorrect and unused.

http://d.puremagic.com/issues/show_bug.cgi?id=2328


dsimcha@yahoo.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |critical
            Version|2.018                       |1.039




------- Comment #1 from dsimcha@yahoo.com  2009-01-25 22:15 -------
No longer relevant to D2, but should still be fixed in D1.


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=2328



--- Comment #2 from github-bugzilla@puremagic.com 2012-04-25 01:43:15 PDT ---
Commit pushed to phobos-1.x at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/e13d211422f71a681f08bf28df2c54bd7bf9dc88 fix Issue 2328 - setTypeInfo in gc.d backwards.

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