https://issues.dlang.org/show_bug.cgi?id=21357

johanengelen@weka.io changed:

           What    |Removed                     |Added
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           Keywords|                            |industry, wrong-code

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https://issues.dlang.org/show_bug.cgi?id=21357

Iain Buclaw <ibuclaw@gdcproject.org> changed:

           What    |Removed                     |Added
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                 CC|                            |ibuclaw@gdcproject.org

--- Comment #1 from Iain Buclaw <ibuclaw@gdcproject.org> ---
(In reply to johanengelen from comment #0)
> The problem is the following:
> 1. BatchState is a large struct, which means that `BatchState.copy()` is
> passed a pointer to a caller-allocated struct to store its return value
> (instead of returning a value through a register).

I wouldn't count that as a problem, returning large structs is always done using a call slot optimization. It would be more likely whether the callee copies into it or uses the return address directly.  The latter elides a copy, but I don't initially see any reason BatchState should elide a copy (it is POD afterall).

Is there an identified regressing commit yet? Or should I trigger a bisect.

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https://issues.dlang.org/show_bug.cgi?id=21357

Boris Carvajal <boris2.9@gmail.com> changed:

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                 CC|                            |boris2.9@gmail.com

--- Comment #2 from Boris Carvajal <boris2.9@gmail.com> ---
Caused by:

commit 68275da1a9785ad0bf15782da6502948171271bd
Author: Martin Kinkelin <noone@nowhere.com>
Date:   Wed May 27 00:58:09 2020 +0200

    Fix Issue 11292 - Cannot re-initialize a const field in postblit

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https://issues.dlang.org/show_bug.cgi?id=21357

--- Comment #3 from Iain Buclaw <ibuclaw@gdcproject.org> ---
(In reply to Boris Carvajal from comment #2)
> Caused by:
> 
> commit 68275da1a9785ad0bf15782da6502948171271bd
> Author: Martin Kinkelin <noone@nowhere.com>
> Date:   Wed May 27 00:58:09 2020 +0200
> 
>     Fix Issue 11292 - Cannot re-initialize a const field in postblit

Confirmed.  The change alters the AssignExp `this.low = this.low.copy()` into a ConstructExp.  This is wrong, postblits don't initialize new memory.

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https://issues.dlang.org/show_bug.cgi?id=21357

Dlang Bot <dlang-bot@dlang.rocks> changed:

           What    |Removed                     |Added
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           Keywords|                            |pull

--- Comment #4 from Dlang Bot <dlang-bot@dlang.rocks> ---
@ibuclaw updated dlang/dmd pull request #11921 "Revert "Fix Issue 11292 - Cannot re-initialize a const field in postblit"" fixing this issue:

- fix Issue 21357 - [REG2.093] postblit aliases old and new struct pointers

https://github.com/dlang/dmd/pull/11921

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https://issues.dlang.org/show_bug.cgi?id=21357

--- Comment #5 from johanengelen@weka.io ---
(In reply to Iain Buclaw from comment #1)
> (In reply to johanengelen from comment #0)
> > The problem is the following:
> > 1. BatchState is a large struct, which means that `BatchState.copy()` is
> > passed a pointer to a caller-allocated struct to store its return value
> > (instead of returning a value through a register).
> 
> I wouldn't count that as a problem,

Neither do I.
The problem is 2 indeed.

-Johan

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https://issues.dlang.org/show_bug.cgi?id=21357

Dlang Bot <dlang-bot@dlang.rocks> changed:

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

--- Comment #6 from Dlang Bot <dlang-bot@dlang.rocks> ---
dlang/dmd pull request #11921 "Revert "Fix Issue 11292 - Cannot re-initialize a const field in postblit"" was merged into master:

- 14b87dbb0f9dfef258bf13041fcacd9dc2d7ac30 by Iain Buclaw:
  fix Issue 21357 - [REG2.093] postblit aliases old and new struct pointers

https://github.com/dlang/dmd/pull/11921

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