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digitalmars.D.bugs - [Issue 6629] New: std.conv.emplace: enforcement is too weak

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6629

           Summary: std.conv.emplace: enforcement is too weak
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: timon.gehr gmx.ch


--- Comment #0 from timon.gehr gmx.ch 2011-09-08 15:35:28 PDT ---
T emplace(T, Args...)(void[] chunk, Args args) if (is(T == class))
{
    enforce(chunk.length >= __traits(classInstanceSize, T),
           new ConvException("emplace: chunk size too small"));
    auto a = cast(size_t) chunk.ptr;

    enforce(a % T.alignof == 0, text(a, " vs. ", T.alignof));
    ...
}

T.alignof is the alignment of the class reference, not the class instance.
Classes have to be 16-byte aligned, but the enforcement checks only for 4 byte
alignment. This results in segmentation faults in user code, even though the
function performs checks.

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next sibling parent d-bugmail puremagic.com writes:
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--- Comment #1 from timon.gehr gmx.ch 2011-09-08 15:58:32 PDT ---
https://github.com/D-Programming-Language/phobos/pull/249

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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timon.gehr gmx.ch changed:

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


--- Comment #2 from timon.gehr gmx.ch 2011-09-09 05:04:22 PDT ---
The enforcement was actually correct, since apparently alignment of
size_t.sizeof is enough.

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prev sibling parent d-bugmail puremagic.com writes:
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timon.gehr gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |FIXED


--- Comment #3 from timon.gehr gmx.ch 2011-09-09 05:53:08 PDT ---
(In reply to comment #2)

 The enforcement was actually correct, since apparently alignment of
 size_t.sizeof is enough.


It is actually too weak, but enforcing 16-byte alignment is not the correct
solution either, see new try at
http://d.puremagic.com/issues/show_bug.cgi?id=6635

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