[C++] template class instantiation

驗證一下, 在template class當中, 如果有method不依靠template class type T, 這樣還是會產生出兩份不一樣的code, 因為template本身在instantiation的時候就會被當作兩個不同的class.

#include <iostream>
template
class Foo
{
public:
    T goo(T a) { return a + a; };
    int foo(int a) { return a;};
};   

int main()
{
    Foo a;
    Foo b;

    a.goo(12);
    b.goo(1.2);
    a.foo(1);
    b.foo(1);
    return 0;
}

可以看到main裡面, _ZN3FooIiE3fooEi, _ZN3FooIdE3fooEi 是被call到兩個不同的function, 就算裡面code是完全一樣的

    .file   "template_gen.cpp"
    .local  _ZStL8__ioinit
    .comm   _ZStL8__ioinit,1,1
    .text
.globl main
    .type   main, @function
main:
.LFB959:
    .cfi_startproc
    .cfi_personality 0x3,__gxx_personality_v0
    pushq   %rbp
    .cfi_def_cfa_offset 16
    movq    %rsp, %rbp
    .cfi_offset 6, -16
    .cfi_def_cfa_register 6
    subq    $16, %rsp
    leaq    -1(%rbp), %rax
    movl    $12, %esi
    movq    %rax, %rdi
    call    _ZN3FooIiE3gooEi
    movsd   .LC0(%rip), %xmm0
    leaq    -2(%rbp), %rax
    movq    %rax, %rdi
    call    _ZN3FooIdE3gooEd
    leaq    -1(%rbp), %rax
    movl    $1, %esi
    movq    %rax, %rdi
    call    _ZN3FooIiE3fooEi
    leaq    -2(%rbp), %rax
    movl    $1, %esi
    movq    %rax, %rdi
    call    _ZN3FooIdE3fooEi
    movl    $0, %eax
    leave
    ret
    .cfi_endproc

...略

_ZN3FooIiE3fooEi:
.LFB962:
    .cfi_startproc
    .cfi_personality 0x3,__gxx_personality_v0
    pushq   %rbp
    .cfi_def_cfa_offset 16
    movq    %rsp, %rbp
    .cfi_offset 6, -16
    .cfi_def_cfa_register 6
    movq    %rdi, -8(%rbp)
    movl    %esi, -12(%rbp)
    movl    -12(%rbp), %eax
    leave
    ret
    .cfi_endproc
.LFE962:
    .size   _ZN3FooIiE3fooEi, .-_ZN3FooIiE3fooEi
    .section    .text._ZN3FooIdE3fooEi,"axG",@progbits,_ZN3FooIdE3fooEi,comdat
    .align 2
    .weak   _ZN3FooIdE3fooEi
    .type   _ZN3FooIdE3fooEi, @function
_ZN3FooIdE3fooEi:
.LFB963:
    .cfi_startproc
    .cfi_personality 0x3,__gxx_personality_v0
    pushq   %rbp
    .cfi_def_cfa_offset 16
    movq    %rsp, %rbp
    .cfi_offset 6, -16
    .cfi_def_cfa_register 6
    movq    %rdi, -8(%rbp)
    movl    %esi, -12(%rbp)
    movl    -12(%rbp), %eax
    leave
    ret
    .cfi_endproc 

...略