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digitalmars.D.bugs - [Issue 4791] New: Assigning a static array to itself should be allowed

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4791

           Summary: Assigning a static array to itself should be allowed
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dsimcha yahoo.com


--- Comment #0 from David Simcha <dsimcha yahoo.com> 2010-09-02 21:48:58 PDT ---
void main() {
    int[2] foo;
    foo = foo;
}

object.Exception: overlapping array copy

This is a ridiculous limitation and is bugs waiting to happen.  (For example,
Bug 4789.)  Even if this requires a simple runtime check before calling
memcpy() or whatever, IMHO it's worth it because the cost of a single pointer
comparison is negligible in almost all cases and for tiny static arrays (where
it might not be negligible) the compiler could just generate regular assignment
instructions that are safe for the overlapping/identical case instead of using
something like memcpy().

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Sep 02 2010
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4791


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc


--- Comment #1 from bearophile_hugs eml.cc 2010-09-03 04:39:48 PDT ---
The only correct syntax to write that code is this, see bug 3971

void main() {
    int[2] foo;
    foo[] = foo[];
}

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prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=4791



--- Comment #2 from David Simcha <dsimcha yahoo.com> 2010-09-03 05:25:43 PDT ---
Yes, and this is a nightmare for generic code.

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