Cpp

tuple memory layout

Source

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#include <map>
#include <functional>
#include <vector>
#include <string>
#include <iostream>

template<typename... Args>
void func(std::tuple<Args...> const &pair) {
    auto &a = std::get<0>(pair);
    auto &b = std::get<1>(pair);
    auto &c = std::get<2>(pair);
    auto &d = std::get<3>(pair);
    std::cout << a << ", " << b << ", " << c << ", " << d << "\n";
}

int main () {
    std::tuple<int, unsigned short, long, long> pair1{128, 256, 655, 65536};
    func(pair1);
    std::cout << "Program end\n";
    return 0;
}

Disassembly

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main:
        subq    $40, %rsp
        movq    $65536, (%rsp)
        movq    $655, 8(%rsp)
        movw    $256, 16(%rsp)
        movl    $128, 20(%rsp)
        movq    %rsp, %rdi
        call    void func<int, unsigned short, long, long>(std::tuple<int, unsigned short, long, long> const&)
        movl    $.LC2, %esi
        movl    $_ZSt4cout, %edi
        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)
        movl    $0, %eax
        addq    $40, %rsp
        ret
 # 元素的排列顺序与声明顺序相反
 # tuple 的 variadic template deduction 造成的(类的继承关系)
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