Compiler patch for runtime reflection

[Robert Jacques]

On Fri, 21 Oct 2011 17:23:17 -0400, Daniel Gibson <metalcaedes at gmail.com> wrote:
> Am 21.10.2011 21:07, schrieb Vladimir Panteleev:
>> Hi,
>>
>> Igor Stepanov has created a patch for DMD and Druntime which adds RTTI
>> information for class and struct members.
>>
>> Example:
>>
>> import std.stdio;
>>
>> class Foo
>> {
>> static void PrintHello()
>> {
>> writeln("Hello");
>> }
>> }
>> void main()
>> {
>> auto info = cast(OffsetTypeInfo_StaticMethod)Foo.classinfo.m_offTi[0];
>> assert(info.name == "PrintHello");
>> auto print = cast(void function())info.pointer;
>> print(); //prints "Hello"
>> }
>>
>> While the inclusion of such functionality into the language remains a
>> disputed matter, would anyone be interested in an unofficial patch for
>> this?
>>
>> Walter: would it be okay if the compiler changes were published as a
>> GitHub fork, or should we stick to patches?
>>
>
> I'd love to see proper runtime reflection support in D, including
> functionality to get information about available methods (their name and
> parameters) and a way to call them.

What do you mean by their 'parameters'? What about overloads? Attributes? Arguments? Argument attributes?

> Something that is close to what Java offers would be great.

And what, exactly does JAVA offer? What works? What doesn't work? What's missing?

> BTW: I don't really see the problem with providing this information
> (overhead-wise) - the information needs to be available once per
> class/struct, but objects of classes just need one pointer to it (other
> types don't even need that because they're not polymorphic and - like
> methods of structs - the address of the information is known at
> compile-time).

1) Unused information is simply bloat: it increases exe size, slows the exe down and increases the runtime memory footprint.
2) On a lot of systems (i.e. consoles, embedded, smart phones, tablets) memory and disk space are both highly constrained resources that you don't want to waste.
3) RTTI provides a back-door into a code-base; one that for many reasons you may want to keep closed.