Re: [ooc-compiler] PROPOSAL: Interface to C++ objects and methods

[Stewart G. <sgr...@ii...>]

Stewart Greenhill wrote:
>> Would it not be simpler to have OOC mangle the symbol names the same 
>> way as the C++ compiler? I realise that is compiler-dependant and I 
>> believe g++ broke ABI recently by changing the mangling algorithm. 
>> Even so the algorithms should be reasonably easy to discover 
>> (especially for g++). There would remain the issue of telling OOC 
>> which algorithm to use.
> 
> 
> I suppose that might work. Within the current oo2c implementation it 
> would need to be possible to access the mangled symbols from C code. I'm 
> not sure if that's possible - presumably the compiler writers take steps 
> to prevent the mangled names colliding with the mangled symbols. 

Ooops! What I meant was that the compiler should prevent "C" names 
colliding with the mangled symbols.

> Certainly, it would be possible at the asm/linker level.

Looks like for GCC it is possible from "C". Given this definition:

class Test {
	int add(int a, int b);
};

int Test::add(int a, int b) {
	return a + b;
}

The compiler generates a symbol named "__ZN1T3addEii". With the 
appropriate definition, this can be called from "C":

#include <stdio.h>

extern int _ZN1T3addEii(void * obj, int a, int b);

int main(int argc, char ** argv) {
	printf("test -> %d\n", _ZN1T3addEii(NULL, 2, 3));
}

Some compiler mangle the names using symbols that are not valid within C 
identifiers, which would prevent this approach from working. See some 
examples here:
http://en.wikipedia.org/wiki/Name_mangling#How_different_compilers_mangle_the_same_functions

Cheers,
   Stewart