I have the C++ code:
int main(){
M* m;
O* o = new IO();
H* h = new H("A");
if(__rdtsc() % 5 == 0){
m = new Y(o, h);
}
else{
m = new Z(o, h);
}
m->my_virtual();
return 1;
}
where the virtual call is represented by this asm:
mov rax,qword ptr [x]
mov rax,qword ptr [rax]
mov rcx,qword ptr [x]
call qword ptr [rax]
It is one more line than I was expecting for the vtable method invoccation. Are all four of the ASM lines specific to the polymorphic call?
How do the above four lines read pseudo-ly?
This is the complete ASM and C++ (the virtual call is made right at the end):
int main(){
add byte ptr [rax-33333334h],bh
rep stos dword ptr [rdi]
mov qword ptr [rsp+0A8h],0FFFFFFFFFFFFFFFEh
M* x;
o* o = new IO();
mov ecx,70h
call operator new (013F6B7A70h)
mov qword ptr [rsp+40h],rax
cmp qword ptr [rsp+40h],0
je main+4Fh (013F69687Fh)
mov rcx,qword ptr [rsp+40h]
call IO::IO (013F6814F6h)
mov qword ptr [rsp+0B0h],rax
jmp main+5Bh (013F69688Bh)
mov qword ptr [rsp+0B0h],0
mov rax,qword ptr [rsp+0B0h]
mov qword ptr [rsp+38h],rax
mov rax,qword ptr [rsp+38h]
mov qword ptr [o],rax
H* h = new H("A");
mov ecx,150h
call operator new (013F6B7A70h)
mov qword ptr [rsp+50h],rax
cmp qword ptr [rsp+50h],0
je main+0CEh (013F6968FEh)
lea rax,[rsp+58h]
mov qword ptr [rsp+80h],rax
lea rdx,[ec_table+11Ch (013F7C073Ch)]
mov rcx,qword ptr [rsp+80h]
call std::basic_string<char,std::char_traits<char>,std::allocator<char> >::basic_string<char,std::char_traits<char>,std::allocator<char> > (013F681104h)
mov qword ptr [rsp+0B8h],rax
mov rdx,qword ptr [rsp+0B8h]
mov rcx,qword ptr [rsp+50h]
call H::H (013F6826A3h)
mov qword ptr [rsp+0C0h],rax
jmp main+0DAh (013F69690Ah)
mov qword ptr [rsp+0C0h],0
mov rax,qword ptr [rsp+0C0h]
mov qword ptr [rsp+48h],rax
mov rax,qword ptr [rsp+48h]
mov qword ptr [h],rax
if(__rdtsc() % 5 == 0){
rdtsc
shl rdx,20h
or rax,rdx
xor edx,edx
mov ecx,5
div rax,rcx
mov rax,rdx
test rax,rax
jne main+175h (013F6969A5h)
x = new Y(o, h);
mov ecx,18h
call operator new (013F6B7A70h)
mov qword ptr [rsp+90h],rax
cmp qword ptr [rsp+90h],0
je main+14Ah (013F69697Ah)
mov r8,qword ptr [h]
mov rdx,qword ptr [o]
mov rcx,qword ptr [rsp+90h]
call Y::Y (013F681B4Fh)
mov qword ptr [rsp+0C8h],rax
jmp main+156h (013F696986h)
mov qword ptr [rsp+0C8h],0
mov rax,qword ptr [rsp+0C8h]
mov qword ptr [rsp+88h],rax
mov rax,qword ptr [rsp+88h]
mov qword ptr [x],rax
}
else{
jmp main+1DCh (013F696A0Ch)
x = new Z(o, h);
mov ecx,18h
call operator new (013F6B7A70h)
mov qword ptr [rsp+0A0h],rax
cmp qword ptr [rsp+0A0h],0
je main+1B3h (013F6969E3h)
mov r8,qword ptr [h]
mov rdx,qword ptr [o]
mov rcx,qword ptr [rsp+0A0h]
call Z::Z (013F68160Eh)
mov qword ptr [rsp+0D0h],rax
jmp main+1BFh (013F6969EFh)
mov qword ptr [rsp+0D0h],0
mov rax,qword ptr [rsp+0D0h]
mov qword ptr [rsp+98h],rax
mov rax,qword ptr [rsp+98h]
mov qword ptr [x],rax
}
x->my_virtual();
mov rax,qword ptr [x]
mov rax,qword ptr [rax]
mov rcx,qword ptr [x]
call qword ptr [rax]
return 1;
mov eax,1
}