[Issue 14931] switch doesn't work with any pointers

https://issues.dlang.org/show_bug.cgi?id=14931

Andrei Alexandrescu <andrei@erdani.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|x86                         |All
                 OS|Mac OS X                    |All

--- Comment #1 from Andrei Alexandrescu <andrei@erdani.com> ---
Consider:

void fun(T)() {}
alias Ptr = void function() pure nothrow @nogc @safe;

void main(string[] argv) {
    enum a = &fun!int;
    static immutable Ptr b = &fun!double;
    static assert(a != b);

    Ptr p;
    switch (p)
    {
        case a: break;
        case b: break;
    }
}

The first three lines in main() clarify that pointers to functions can be evaluated and compared during compilation. Yet the switch statement does not work.

This applies to general pointers - switch does not work with any pointers, yet it should work because pointers are comparable and there exist constant pointers.

--

https://issues.dlang.org/show_bug.cgi?id=14931 Sobirari Muhomori <dfj1esp02@sneakemail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- URL| |http://forum.dlang.org/post | |/mqvbcl$1k2q$2@digitalmars. | |com --- Comment #2 from Sobirari Muhomori <dfj1esp02@sneakemail.com> --- As I understand from the discussion, the idea is to not only compile it, but to generate a jump table for such switch statement instead of being a syntax sugar for if-else chain? --

https://issues.dlang.org/show_bug.cgi?id=14931 --- Comment #3 from Andrei Alexandrescu <andrei@erdani.com> --- Yah, accept it and subject it to the usual assumptions and optimizations that go for equivalent integral-based switch statements. --

https://issues.dlang.org/show_bug.cgi?id=14931 yebblies <yebblies@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |yebblies@gmail.com --- Comment #4 from yebblies <yebblies@gmail.com> --- (In reply to Andrei Alexandrescu from comment #3) > Yah, accept it and subject it to the usual assumptions and optimizations that go for equivalent integral-based switch statements. There is no guarantee that integral switches get turned into jump tables. --

https://issues.dlang.org/show_bug.cgi?id=14931 --- Comment #5 from Andrei Alexandrescu <andrei@erdani.com> --- (In reply to yebblies from comment #4) > (In reply to Andrei Alexandrescu from comment #3) > > Yah, accept it and subject it to the usual assumptions and optimizations that go for equivalent integral-based switch statements. > > There is no guarantee that integral switches get turned into jump tables. Understood, thanks. Just handle them the same is all. --

https://issues.dlang.org/show_bug.cgi?id=14931 --- Comment #6 from yebblies <yebblies@gmail.com> --- (In reply to Andrei Alexandrescu from comment #5) > (In reply to yebblies from comment #4) > > (In reply to Andrei Alexandrescu from comment #3) > > > Yah, accept it and subject it to the usual assumptions and optimizations that go for equivalent integral-based switch statements. > > > > There is no guarantee that integral switches get turned into jump tables. > > Understood, thanks. Just handle them the same is all. We should be able to support pointer switch, but we can't do pointer switch jump tables since the pointer's integer representation isn't known until link time. --

https://issues.dlang.org/show_bug.cgi?id=14931 ZombineDev <petar.p.kirov@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |petar.p.kirov@gmail.com --- Comment #7 from ZombineDev <petar.p.kirov@gmail.com> --- Is it possible to generate a jump table with placeholders and fill them at link time? --

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