On Sunday, 3 January 2016 at 19:29:05 UTC, Martin Nowak wrote:
There is a bug.

You should never do this b/c of iterator/range invalidation.

foreach (key; aa.keys)

I've recently hit this when trying to remove some of the elements from an AA while iterating over it. It's easy to forget that it is not allowed, especially when working on more complex algorithms. Accidentally, it worked all fine even with large data sets with DMD 2.069, but with GDC mysterious segfaults appeared - the first thought in such case was obviously a bug in GDC or in the older front-end.

However, this is a very convenient, natural and intuitive syntax for something that is needed quite frequently, yet this code breaks silently in non-predictable ways. There are already registered issues concerning this (or similar with insertion) problem, including:


I've personally encountered segfaults, infinite loops, programs producing incorrect results. Some solutions to this were proposed in the bug reports - either: a) explicitly allow removing during iteration, and make sure it always works, or b) explicitly disallow removing during iteration, and always throw an Error whenever it is attempted. In some cases it could even be detectable in compile time.

And I don't mean including a single sentence about this somewhere in the docs. I mean an error reported by the compiler and/or runtime. The runtime checks could be disabled for -release, but there should be at least an option to detect such errors. Probably the worst part of it is that you're free to wrap it in @safe, while it's not safe at all.

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