http://d.puremagic.com/issues/show_bug.cgi?id=10789

           Summary: Struct destructor erroneously called
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: sludwig@outerproduct.org


--- Comment #0 from Sönke Ludwig <sludwig@outerproduct.org> 2013-08-09 22:54:25 PDT ---
The attached program simulates a simple reference counted struct. 'fun' is supposed to return a newly initialized S with a count of 1. Instead it calls the destructor dropping the count to zero and then returns a copy of the initialized struct. Leaving out the 'if' statment and returning the fresh 'S' directly does not exibit this behavior.

This issue is critical as it has a high probability to indroduce hard to detect/track down bugs when automatic reference counting is used.

Tested on DMD 2.063.2/Win32 and /Win64 and DMD master/Win32.

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--- Comment #1 from Sönke Ludwig <sludwig@outerproduct.org> 2013-08-09 22:55:04 PDT ---
Created an attachment (id=1241)
Reproduction case

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Maxim Fomin <maxim@maxim-fomin.ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maxim@maxim-fomin.ru


--- Comment #2 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-08-10 00:44:27 PDT ---
Reduced:

extern(C) int printf(const char*, ...);

struct S {
    static int count;

    this(int ignoreme)
    {
      int oldcount = count;
        printf("%X ctor %d=>%d\n", &this, oldcount, ++count);
    }

    ~this()
    {
      int oldcount = count;
        printf("%X dtor %d=>%d\n", &this, oldcount, --count);
    }

    this(this)
    {
      int oldcount = count;
        printf("%X postblit %d=>%d\n", &this, oldcount, ++count);
    }
}

S fun()
{
   S s1 = S(42), s2 = S(24);
    if (true) return s1;
   else return s2;
}

void main()
{
   S s = fun();
}

In case of if(true) compiler does not insert postblit call.

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--- Comment #3 from Sönke Ludwig <sludwig@outerproduct.org> 2013-08-17 07:31:21 PDT ---
I digged a little in the DMD sources and found a commit by Kenji Hara that at
least affects this example and has a commented out code block that looks a
little suspicious :
https://github.com/D-Programming-Language/dmd/commit/b4bc25d72e601436f3999abc5c9c31e464385052#L4R1241

Changing "#if 0//DMDV2" back to "#if DMDV2" inserts a proper postblit call, but then the returned t has its initialized field set to false. This does not happen with the "#if 0" AFAICS. Unfortunately I know far to less about the mechanics at work there to make an informed attempt to fix this.

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Maxim Fomin <maxim@maxim-fomin.ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |regression


--- Comment #4 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-08-17 09:26:45 PDT ---
(In reply to comment #3)
> I digged a little in the DMD sources and found a commit by Kenji Hara that at
> least affects this example and has a commented out code block that looks a
> little suspicious :
> https://github.com/D-Programming-Language/dmd/commit/b4bc25d72e601436f3999abc5c9c31e464385052#L4R1241
> 
> Changing "#if 0//DMDV2" back to "#if DMDV2" inserts a proper postblit call, but then the returned t has its initialized field set to false. This does not happen with the "#if 0" AFAICS. Unfortunately I know far to less about the mechanics at work there to make an informed attempt to fix this.

Sounds like a regression.

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #5 from Kenji Hara <k.hara.pg@gmail.com> 2013-09-03 21:45:29 PDT ---
https://github.com/D-Programming-Language/dmd/pull/2523

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--- Comment #6 from github-bugzilla@puremagic.com 2013-09-03 22:53:21 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/4ca445bb2564997b80d5c00c6dfc1daeff1e30af fix Issue 10789 - Struct destructor erroneously called

https://github.com/D-Programming-Language/dmd/commit/cfffc9b02fed9366babb6712cba7d6f26c18df6e Merge pull request #2523 from 9rnsr/fix10789

[REG2.061] Issue 10789 - Struct destructor erroneously called

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Walter Bright <bugzilla@digitalmars.com> changed:

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


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Sönke Ludwig <sludwig@outerproduct.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |


--- Comment #7 from Sönke Ludwig <sludwig@outerproduct.org> 2013-09-29 04:38:40 PDT ---
The original test case still fails on DMD HEAD:

---
0018FD74 this() 0
0018FD75 this(this) 1
0018FD74 ~this() 2
0018FD9C ~this() 1
core.exception.AssertError@app(47): Assertion failure
---

This is due to the last destructor running on an uninitialized instance
(initialized == false).

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--- Comment #8 from Kenji Hara <k.hara.pg@gmail.com> 2013-09-29 08:36:03 PDT ---
(In reply to comment #7)
> The original test case still fails on DMD HEAD:
> 
> ---
> 0018FD74 this() 0
> 0018FD75 this(this) 1
> 0018FD74 ~this() 2
> 0018FD9C ~this() 1
> core.exception.AssertError@app(47): Assertion failure
> ---
> 
> This is due to the last destructor running on an uninitialized instance
> (initialized == false).

To me it looks like that the original test case contains a bug.

In S.this(this), `initialized` field is incorrectly set to false. It will stop to decrement S.count at the destruction of the copied objects. Therefore the last assertion in main fails because S.count == 1.

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