cross platform - How to obtain a pointer out of a C++ vtable? -

say have c++ class like:

class foo {  public:   virtual ~foo() {}   virtual dosomething() = 0; }; 

the c++ compiler translates call vtable lookup:

foo* foo;  // translated c++ to: //   foo->vtable->dosomething(foo); foo->dosomething(); 

suppose writing jit compiler , wanted obtain address of dosomething() function particular instance of class foo, can generate code jumps directly instead of doing table lookup , indirect branch.

my questions are:

1. is there standard c++ way (i'm sure answer no, wanted ask sake of completeness).

2. is there remotely compiler-independent way of doing this, library has implemented provides api accessing vtable?

i'm open hacks, if work. example, if created own derived class , determine address of dosomething method, assume vtable first (hidden) member of foo , search through vtable until find pointer value. however, don't know way of getting address: if write &derivedfoo::dosomething pointer-to-member, totally different.

maybe turn pointer-to-member vtable offset. when compile following:

class foo {  public:   virtual ~foo() {}   virtual void dosomething() = 0; };  void foo(foo *f, void (foo::*member)()) {   (f->*member)(); } 

on gcc/x86-64, assembly output:

disassembly of section .text:  0000000000000000 <_z3foop3fooms_fvve>:    0:   40 f6 c6 01             test   sil,0x1    4:   48 89 74 24 e8          mov    qword ptr [rsp-0x18],rsi    9:   48 89 54 24 f0          mov    qword ptr [rsp-0x10],rdx    e:   74 10                   je     20 <_z3foop3fooms_fvve+0x20>   10:   48 01 d7                add    rdi,rdx   13:   48 8b 07                mov    rax,qword ptr [rdi]   16:   48 8b 74 30 ff          mov    rsi,qword ptr [rax+rsi*1-0x1]   1b:   ff e6                   jmp    rsi   1d:   0f 1f 00                nop    dword ptr [rax]   20:   48 01 d7                add    rdi,rdx   23:   ff e6                   jmp    rsi 

i don't understand what's going on here, if reverse-engineer or use abi spec generate fragment above each separate platform, way of obtaining pointer out of vtable.

why think &derivedfoo::dosomething different? isn't you're asking for? way think it, call derivedfoo::dosomething() call same function, passing different pointer. vtable merely distinguishes between different types derived foo, not instances.