• d-bugmail puremagic.com (44/44) Oct 31 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6869
• d-bugmail puremagic.com (9/9) Oct 31 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6869
• d-bugmail puremagic.com (9/9) Jan 31 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6869
• d-bugmail puremagic.com (10/10) Jan 31 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6869
• d-bugmail puremagic.com (9/9) Jan 31 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6869

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6869

           Summary: Disallow array to pointer cast
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



This is a spinoff of bug 3990

In DMD 2.056 this code compiles:

void main() {
   int[] a1 = [5, 4, 3];
   int* p1 = cast(int*)a1; // no compile error here
}


Similar code using user-created struct doesn't compile:


struct Foo {
    int* p;
    size_t n;
}
void main() {
    Foo f;
    auto x = cast(int*)f; // compile error here
}


I don't see the need to accept this cast, because allowing the array to pointer
cast means introducing/leaving an useless special case, and there in practice
this special case is not useful because arrays have the ptr property:


struct Foo {
    int* p;
    size_t n;
}
void main() {
    Foo f;
    auto x = f.ptr; // OK
}


So I think cast(int*)a1 should be forbidden.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6869




See some discussion:

http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=148090

An answer:

http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=148099

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6869


yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yebblies gmail.com
           Severity|normal                      |enhancement


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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6869


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|enhancement                 |normal



Reverted to bug, this isn't an enhancement, it's a bug.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6869




How is it a bug?  Implicit conversions from arrays to pointers have been
deprecated, but as far as I know this is an intentional feature of D,
regardless of if it's a useful/bug prone one or not.  Is there any reason you
know of why this is not working as intended?

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