http://d.puremagic.com/issues/show_bug.cgi?id=11051

           Summary: Unmatched case in a final switch should throw in both
                    release and non-release mode
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: andrej.mitrovich@gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-09-16 07:14:09 PDT ---
-----
module test;

import std.stdio;

enum E { a }

string get()
{
    auto e = cast(E)123;
    final switch(e)
    {
        case E.a:
            return "foobar";
    }
}

void main()
{
    writeln(get());
}
-----

$ dmd -run test.d
> core.exception.SwitchError@test(10): No appropriate switch clause found

$ dmd -release -run test.d
> x ↑

The release switch ends up making get() return garbage.

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bearophile_hugs@eml.cc changed:

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


--- Comment #1 from bearophile_hugs@eml.cc 2013-09-16 07:29:13 PDT ---
Letting it throw an error in non-release mode kills some of optimization you are supposed to have using a final switch, so I am not sure it's a good idea.

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--- Comment #2 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-09-16 07:34:50 PDT ---
(In reply to comment #1)
> Letting it throw an error in non-release mode kills some of optimization you are supposed to have using a final switch, so I am not sure it's a good idea.

You mean *in release mode*, right? It currently throws in non-release mode, it doesn't throw in release mode.

But what is the above code supposed to do if not throw in both cases?

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--- Comment #3 from bearophile_hugs@eml.cc 2013-09-16 07:42:32 PDT ---
(In reply to comment #2)
> You mean *in release mode*, right?

Right, sorry.


> It currently throws in non-release mode, it doesn't throw in release mode.

This seems good to me. If you want to convert an untrusted value to an enum safely you should use std.conv.to:


import std.stdio, std.conv;

enum E { a }

string get() {
    //immutable e = cast(E)123;
    immutable e = to!E(123);
    final switch(e) {
        case E.a: return "foobar";
    }
}
void main() {
    get.writeln;
}

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--- Comment #4 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-09-16 07:56:31 PDT ---
(In reply to comment #3)
> This seems good to me.

No, returning garbage is not good. At the very least I expect a HALT instruction after the final switch for code which should not reach that point.

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Maxim Fomin <maxim@maxim-fomin.ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maxim@maxim-fomin.ru


--- Comment #5 from Maxim Fomin <maxim@maxim-fomin.ru> 2013-09-16 08:08:27 PDT ---
(In reply to comment #3)
> (In reply to comment #2)
> > You mean *in release mode*, right?
> 
> Right, sorry.
> 
> 
> > It currently throws in non-release mode, it doesn't throw in release mode.
> 
> This seems good to me. If you want to convert an untrusted value to an enum safely you should use std.conv.to:
> 
> 
> import std.stdio, std.conv;
> 
> enum E { a }
> 
> string get() {
>     //immutable e = cast(E)123;
>     immutable e = to!E(123);
>     final switch(e) {
>         case E.a: return "foobar";
>     }
> }
> void main() {
>     get.writeln;
> }

No, you will run into memory errors. Either dmd should still throw SwitchError or insert halt instruction.

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--- Comment #6 from Orvid King <blah38621@gmail.com> 2013-09-16 09:03:51 PDT ---
(In reply to comment #1)
> Letting it throw an error in non-release mode kills some of optimization you are supposed to have using a final switch, so I am not sure it's a good idea.

But an error isn't covered by the nothrow contract, so you wouldn't be able to optimize that anyways.

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