006模板的编译机制_对模板进行两次编译

其他 2019-04-24 10:51:05 阅读次数: 0 
#include<iostream>
using namespace std;
/*

函数模板机制结论
编译器并不是把函数模板处理成能够处理任意类的函数
编译器从函数模板通过具体类型产生不同的函数
编译器会对函数模板进行两次编译
在声明的地方对模板代码本身进行编译；在调用的地方对参数替换后的代码进行编译。

根据调用产生不同类型的函数，本质上是c++编译器帮我们做了函数的重写，（本例生成两个函数）
*/
// 函数的业务逻辑 一样 
// 函数的参数类型 不一样
void myswap01(int &a, int &b)
{
	int c = 0;
	c = a;
	a = b;
	b = c;
}

void myswap02(char &a, char &b)
{
	char c = 0;
	c = a;
	a = b;
	b = c;
}

template <typename T>
void myswap(T&a,T&b)
{
	T c = 0;
	c = a;
	a = b;
	b = c;
	cout << "hello...我是函数模板，欢迎call我" << endl;
}

int main(void)
{
	{
		int x = 10;
		int y = 20;
		myswap<int>(x, y);//调用模板函数,显示调用
		cout << "x=" << x << endl;
		cout << "y=" << y << endl;
	}

	{
		char a = 'a';
		char b = 'b';
		myswap<char>(a, b);
		cout << "a=" << a << endl;
		cout << "b=" << b << endl;

	}
	system("pause");
	return 0;
}
/*
模板本质剖析.cpp
把此文档编译成汇编

预处理（Pre-Processing）
编译（Compiling）
汇编（Assembling）
链接（Linking）
Gcc *.c -o 1exe (总的编译步骤)
Gcc -E 1.c -o 1.i  //宏定义进行宏展开
Gcc -S 1.i -o 1.s
Gcc -c 1.s -o 1.o
Gcc 1.o -o 1exe
*/

/*
本程序主要是为了编译成汇编语言来查看
模板的机制编译器会对函数模板进行两次编译.cpp

二次编译：第一次扫描函数模板的语法，有没有语法错误，可能生成函数头
当调用函数时生成具体的函数。

加一个断点 -调试-窗口-反汇编
*/

可以看到函数被调用了4次

	
.file	"006\346\250\241\346\235\277\347\232\204\347\274\226\350\257\221\346\234\272\345\210\266_\345\257\271\346\250\241\346\235\277\350\277\233\350\241\214\344\270\244\346\254\241\347\274\226\350\257\221.cpp"
	.text
	.section	.rodata
	.type	_ZStL19piecewise_construct, @object
	.size	_ZStL19piecewise_construct, 1
_ZStL19piecewise_construct:
	.zero	1
	.local	_ZStL8__ioinit
	.comm	_ZStL8__ioinit,1,1
	.text
	.globl	_Z8myswap01RiS_
	.type	_Z8myswap01RiS_, @function
_Z8myswap01RiS_:
.LFB1493:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movq	%rdi, -24(%rbp)
	movq	%rsi, -32(%rbp)
	movl	$0, -4(%rbp)
	movq	-24(%rbp), %rax
	movl	(%rax), %eax
	movl	%eax, -4(%rbp)
	movq	-32(%rbp), %rax
	movl	(%rax), %edx
	movq	-24(%rbp), %rax
	movl	%edx, (%rax)
	movq	-32(%rbp), %rax
	movl	-4(%rbp), %edx
	movl	%edx, (%rax)
	nop
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1493:
	.size	_Z8myswap01RiS_, .-_Z8myswap01RiS_
	.globl	_Z8myswap02RcS_
	.type	_Z8myswap02RcS_, @function
_Z8myswap02RcS_:
.LFB1494:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movq	%rdi, -24(%rbp)
	movq	%rsi, -32(%rbp)
	movb	$0, -1(%rbp)
	movq	-24(%rbp), %rax
	movzbl	(%rax), %eax
	movb	%al, -1(%rbp)
	movq	-32(%rbp), %rax
	movzbl	(%rax), %edx
	movq	-24(%rbp), %rax
	movb	%dl, (%rax)
	movq	-32(%rbp), %rax
	movzbl	-1(%rbp), %edx
	movb	%dl, (%rax)
	nop
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1494:
	.size	_Z8myswap02RcS_, .-_Z8myswap02RcS_
	.section	.rodata
.LC0:
	.string	"x="
.LC1:
	.string	"y="
.LC2:
	.string	"a="
.LC3:
	.string	"b="
.LC4:
	.string	"pause"
	.text
	.globl	main
	.type	main, @function
main:
.LFB1496:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$16, %rsp
	movq	%fs:40, %rax
	movq	%rax, -8(%rbp)
	xorl	%eax, %eax
	movl	$10, -16(%rbp)
	movl	$20, -12(%rbp)
	leaq	-12(%rbp), %rdx
	leaq	-16(%rbp), %rax
	movq	%rdx, %rsi
	movq	%rax, %rdi
	call	_Z6myswapIiEvRT_S1_
	leaq	.LC0(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movl	-16(%rbp), %eax
	movl	%eax, %esi
	movq	%rdx, %rdi
	call	_ZNSolsEi@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	leaq	.LC1(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movl	-12(%rbp), %eax
	movl	%eax, %esi
	movq	%rdx, %rdi
	call	_ZNSolsEi@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	movb	$97, -16(%rbp)
	movb	$98, -12(%rbp)
	leaq	-12(%rbp), %rdx
	leaq	-16(%rbp), %rax
	movq	%rdx, %rsi
	movq	%rax, %rdi
	call	_Z6myswapIcEvRT_S1_
	leaq	.LC2(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movzbl	-16(%rbp), %eax
	movsbl	%al, %eax
	movl	%eax, %esi
	movq	%rdx, %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_c@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	leaq	.LC3(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movzbl	-12(%rbp), %eax
	movsbl	%al, %eax
	movl	%eax, %esi
	movq	%rdx, %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_c@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	leaq	.LC4(%rip), %rdi
	call	system@PLT
	movl	$0, %eax
	movq	-8(%rbp), %rcx
	xorq	%fs:40, %rcx
	je	.L5
	call	__stack_chk_fail@PLT
.L5:
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1496:
	.size	main, .-main
	.section	.rodata
	.align 8
.LC5:
	.string	"hello...\316\322\312\307\272\257\312\375\304\243\260\345\243\254\273\266\323\255call\316\322"
	.section	.text._Z6myswapIiEvRT_S1_,"axG",@progbits,_Z6myswapIiEvRT_S1_,comdat
	.weak	_Z6myswapIiEvRT_S1_
	.type	_Z6myswapIiEvRT_S1_, @function
_Z6myswapIiEvRT_S1_:
.LFB1733:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$32, %rsp
	movq	%rdi, -24(%rbp)
	movq	%rsi, -32(%rbp)
	movl	$0, -4(%rbp)
	movq	-24(%rbp), %rax
	movl	(%rax), %eax
	movl	%eax, -4(%rbp)
	movq	-32(%rbp), %rax
	movl	(%rax), %edx
	movq	-24(%rbp), %rax
	movl	%edx, (%rax)
	movq	-32(%rbp), %rax
	movl	-4(%rbp), %edx
	movl	%edx, (%rax)
	leaq	.LC5(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	nop
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1733:
	.size	_Z6myswapIiEvRT_S1_, .-_Z6myswapIiEvRT_S1_
	.section	.text._Z6myswapIcEvRT_S1_,"axG",@progbits,_Z6myswapIcEvRT_S1_,comdat
	.weak	_Z6myswapIcEvRT_S1_
	.type	_Z6myswapIcEvRT_S1_, @function
_Z6myswapIcEvRT_S1_:
.LFB1737:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$32, %rsp
	movq	%rdi, -24(%rbp)
	movq	%rsi, -32(%rbp)
	movb	$0, -1(%rbp)
	movq	-24(%rbp), %rax
	movzbl	(%rax), %eax
	movb	%al, -1(%rbp)
	movq	-32(%rbp), %rax
	movzbl	(%rax), %edx
	movq	-24(%rbp), %rax
	movb	%dl, (%rax)
	movq	-32(%rbp), %rax
	movzbl	-1(%rbp), %edx
	movb	%dl, (%rax)
	leaq	.LC5(%rip), %rsi
	leaq	_ZSt4cout(%rip), %rdi
	call	_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@PLT
	movq	%rax, %rdx
	movq	_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_@GOTPCREL(%rip), %rax
	movq	%rax, %rsi
	movq	%rdx, %rdi
	call	_ZNSolsEPFRSoS_E@PLT
	nop
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1737:
	.size	_Z6myswapIcEvRT_S1_, .-_Z6myswapIcEvRT_S1_
	.text
	.type	_Z41__static_initialization_and_destruction_0ii, @function
_Z41__static_initialization_and_destruction_0ii:
.LFB1988:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$16, %rsp
	movl	%edi, -4(%rbp)
	movl	%esi, -8(%rbp)
	cmpl	$1, -4(%rbp)
	jne	.L10
	cmpl	$65535, -8(%rbp)
	jne	.L10
	leaq	_ZStL8__ioinit(%rip), %rdi
	call	_ZNSt8ios_base4InitC1Ev@PLT
	leaq	__dso_handle(%rip), %rdx
	leaq	_ZStL8__ioinit(%rip), %rsi
	movq	_ZNSt8ios_base4InitD1Ev@GOTPCREL(%rip), %rax
	movq	%rax, %rdi
	call	__cxa_atexit@PLT
.L10:
	nop
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1988:
	.size	_Z41__static_initialization_and_destruction_0ii, .-_Z41__static_initialization_and_destruction_0ii
	.type	_GLOBAL__sub_I__Z8myswap01RiS_, @function
_GLOBAL__sub_I__Z8myswap01RiS_:
.LFB1989:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movl	$65535, %esi
	movl	$1, %edi
	call	_Z41__static_initialization_and_destruction_0ii
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1989:
	.size	_GLOBAL__sub_I__Z8myswap01RiS_, .-_GLOBAL__sub_I__Z8myswap01RiS_
	.section	.init_array,"aw"
	.align 8
	.quad	_GLOBAL__sub_I__Z8myswap01RiS_
	.hidden	__dso_handle
	.ident	"GCC: (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0"
	.section	.note.GNU-stack,"",@progbits

猜你喜欢

转载自blog.csdn.net/baixiaolong1993/article/details/89482507
今日推荐
周排行
LRU cache算法
windows10, 自带的OpenSSH, key权限问题, 文件权限问题
测试用例书写方法
HIVE-默认分隔符的（linux系统的特殊字符）查看，输入和修改
最贵的AMD 7nm显卡来了！这设计 够狂野
java多线程简单demo
[ 转载 ]在Android系统上使用busybox——最简单的方法
QT connect学习
BFSIFT算法分析
Xcode10：library not found for -lstdc++.6.0.9 临时解决
每日归档
更多
2024-08-06(0)
2024-08-05(0)
2024-08-04(0)
2024-08-03(0)
2024-08-02(0)
2024-08-01(0)
2024-07-31(0)
2024-07-30(0)
2024-07-29(0)
2024-07-28(0)

代码天地 © 2018 codetd.com

境外服务器   最新电视剧2022