dlib 0.19.1 seems to be failing linking with ldc2

[jeff thompson]

On Friday, 31 July 2020 at 20:07:26 UTC, Dennis wrote:
> On Friday, 31 July 2020 at 14:17:14 UTC, jeff thompson wrote:
>> dlib.lib(dlib.audio.io.wav.obj) : error LNK2019: unresolved 
>> external symbol 
>> _D4core8internal7switch___T14__switch_errorZQrFNaNbNiNfAyamZv 
>> referenced in function 
>> _D3std6format__T10printFloatTfTaZQrFNaNfNkAafSQBsQBr__T10FormatSpecTaZQpEQCtQCs12RoundingModeZQCa
>> dlib.lib(dlib.filesystem.local.obj) : error LNK2001: 
>> unresolved external symbol 
>> _D4core8internal7switch___T14__switch_errorZQrFNaNbNiNfAyamZv
>> .dub\build\application-debug-windows-x86_64-ldc_2092-316AB5B187D20C1F6AFBA496E604908D\test.exe : fatal error LNK1120: 1 unresolved externals
>
>
> The first thing you want to do is demangle the symbols so you 
> know what they really are.
> You can use the tool `ddemangle` for that:
> ```
> echo 
> '_D3std6format__T10printFloatTfTaZQrFNaNfNkAafSQBsQBr__T10FormatSpecTaZQpEQCtQCs12RoundingModeZQCa' | ddemangle
> ```
>
> You'll find that this symbol is missing:
>
> pure nothrow @nogc @safe void 
> core.internal.switch_.__switch_error!().__switch_error(immutable(char)[], ulong)
>
> And it's used in this function:
>
> pure @safe char[] std.format.printFloat!(float, 
> char).printFloat(return char[], float, 
> std.format.FormatSpec!(char).FormatSpec, 
> std.format.RoundingMode)
>
> The switch_error function is called when none of the cases of a 
> `final switch` apply. There is a final switch in 
> std.format.printFloat:
> https://github.com/ldc-developers/phobos/blob/c43cafe53746a07dee8fa9e00d3a2256c7f05506/std/format.d#L7096
>
> So why is the compiler not emitting the final switch error 
> template function? I am not sure, it could be a bug, or maybe 
> you have some funky dub settings. You might be able to work 
> around this by defining a final switch in you own code 
> somewhere, or explicitly defining the function.
>
> ```
> pragma(mangle, 
> "_D4core8internal7switch___T14__switch_errorZQrFNaNbNiNfAyamZv")
> void switchError(string file, ulong line) {
>     assert(0, file);
> }
> ```
>
> I hope someone else with more familiarity of how template 
> symbols are emitted can find the root of this problem and give 
> a proper fix.

Thanks! From looking at it, isn't happening in 
dlib.lib(dlib.audio.io.wav.obj)? Also this is with a test program 
with nothing but an empty main and a dependency on dlib 0.19.1. I 
  guess ill post something in their github since it does compile 
and link with dmd