Hello everyone!

I'm new to D.
While playing with around with traits,
I ended up writing this short example:


module test;

class Foo
{
    private int _value = 21;

    void foo()
    {
        import std.traits;

        alias funs = MemberFunctionsTuple!( typeof( this ), "bar" );

        version( crash )
	{
            void function( string ) b = &funs[ 0 ];
            b( "world" );
        }

        funs[ 0 ]( "world" );
    }

    void bar( string s )
    {
        import std.stdio;
        writeln( "hello ", s, "! ", _value );
    }
}

void main()
{
    auto f = new Foo();
    f.foo();
}


My first question is why building this with
dmd test.d

the line:
funs[ 0 ]( "world" );

does not crash, as I would expect because there's no this pointer to access _value when calling the member function.


The second question is why when building with:
dmd -version=crash test.d

the compiler just crashes instead.


These experiments were done with DMD v2.067.0 on Ubuntu x64 and on Windows x64.

Thank you!

On Tuesday, 14 April 2015 at 09:24:04 UTC, Filippo Fantini wrote:
> Hello everyone!
>
> I'm new to D.
> While playing with around with traits,
> I ended up writing this short example:
>
>
> module test;
>
> class Foo
> {
>     private int _value = 21;
>
>     void foo()
>     {
>         import std.traits;
>
>         alias funs = MemberFunctionsTuple!( typeof( this ), "bar" );
>
>         version( crash )
> 	{
>             void function( string ) b = &funs[ 0 ];
>             b( "world" );
>         }
>
>         funs[ 0 ]( "world" );
>     }
>
>     void bar( string s )
>     {
>         import std.stdio;
>         writeln( "hello ", s, "! ", _value );
>     }
> }
>
> void main()
> {
>     auto f = new Foo();
>     f.foo();
> }
>
>
> My first question is why building this with
> dmd test.d
>
> the line:
> funs[ 0 ]( "world" );
>
> does not crash, as I would expect because there's no this pointer to access _value when calling the member function.

That's the same as `Foo.bar("world");`, which also works. The this pointer is passed even though the call does not show it. I don't know if or where this is specified, but I'm pretty sure it's supposed to work like this.

> The second question is why when building with:
> dmd -version=crash test.d
>
> the compiler just crashes instead.

Every compiler crash is a bug. Please report it at <http://issues.dlang.org/>.

On Tuesday, 14 April 2015 at 10:43:16 UTC, anonymous wrote:
> On Tuesday, 14 April 2015 at 09:24:04 UTC, Filippo Fantini wrote:
>> Hello everyone!
>>
>> I'm new to D.
>> While playing with around with traits,
>> I ended up writing this short example:
>>
>>
>> module test;
>>
>> class Foo
>> {
>>    private int _value = 21;
>>
>>    void foo()
>>    {
>>        import std.traits;
>>
>>        alias funs = MemberFunctionsTuple!( typeof( this ), "bar" );
>>
>>        version( crash )
>> 	{
>>            void function( string ) b = &funs[ 0 ];
>>            b( "world" );
>>        }
>>
>>        funs[ 0 ]( "world" );
>>    }
>>
>>    void bar( string s )
>>    {
>>        import std.stdio;
>>        writeln( "hello ", s, "! ", _value );
>>    }
>> }
>>
>> void main()
>> {
>>    auto f = new Foo();
>>    f.foo();
>> }
>>
>>
>> My first question is why building this with
>> dmd test.d
>>
>> the line:
>> funs[ 0 ]( "world" );
>>
>> does not crash, as I would expect because there's no this pointer to access _value when calling the member function.
>
> That's the same as `Foo.bar("world");`, which also works. The this pointer is passed even though the call does not show it. I don't know if or where this is specified, but I'm pretty sure it's supposed to work like this.
>
>> The second question is why when building with:
>> dmd -version=crash test.d
>>
>> the compiler just crashes instead.
>
> Every compiler crash is a bug. Please report it at <http://issues.dlang.org/>.


Thanks.
I've created an issue:
<https://issues.dlang.org/show_bug.cgi?id=14448/>

correct link:

https://issues.dlang.org/show_bug.cgi?id=14448