http://d.puremagic.com/issues/show_bug.cgi?id=10625
Summary: Compiler should warn or disallow using slice syntax in
initialization
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Keywords: accepts-invalid
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nob...@puremagic.com
ReportedBy: andrej.mitrov...@gmail.com
--- Comment #0 from Andrej Mitrovic <andrej.mitrov...@gmail.com> 2013-07-12
09:57:21 PDT ---
-----
void main()
{
int[] source = [0, 1];
int[] arr1 = new int[](2);
arr1[] = source[];
assert(arr1 !is source); // ok
int[] arr2 = source[]; // looks like a copy
assert(arr2 !is arr2); // assert fails: but in fact it's not!
}
-----
The 'int[] arr2 = source[];' syntax appears as though the source contents are
copied into arr2, but in fact this is the same code as 'int[] arr2 = source;'.
Since [] has a very special meaning, the above should either:
1) Become an actual deep copy, meaning arr2 would have to allocate space first
and then copy contents. This would be a breaking and negative change due to
performance implications.
2) Not compile. It looks like a deep copy but it isn't, and this can cause
issues down the road (for example using memcpy or even OpenGL functions can
create hard to track problems due to using the source and target arrays which
point to the same memory).
I'd vote heavily towards 2.
Of course one can always use 'int[] arr2 = source.dup'.
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