总结：1.const重载主要是通过能否对传入的参数进行修改为判断的。2.const参数重载和const函数重载机制都是一样的，因为对于const 函数重载可看做是对隐含的指针this的参数重载。3.重载是在编译阶段已经完成，对于汇编和链接来说透明的。
TAG: 汇编 const 重载
书上和网上在很多地方都对const 的重载做了一些解释，但感觉都不是很详细。还有很多同学在不同的地方发问关于const 重载的问题，这里我又重新看了一下，做了一个简单的分析也可能有不对的地方，欢迎讨论。
所 谓重载，是指允许存在多个同名函数，而这些函数的参数表不同，即函数名相同但函数的签名不同。重载并不是面向对象编程的特有属性，这是因为重载是在编译阶 段实现的，编译器根据函数不同的参数表，对同名函数的名称做修饰，然后这些同名函数就成了不同的函数（这一点稍后有例子）。了
Const 参数重载解析：
关于const 重载几乎在所有c++的书中者提到过但大部分只是一句话，例如在《C++ primer》一书中这样描述：“可基于函数的引用形参是指向 const 对象还是指向非 const 对象，实现函数重载。将引用形参定义为 const 来重载函数是合法的，因为编译器可以根据实参是否为 const 确定调用哪一个函数。”
但是这一段描述并没有给出引用、指针和值传递前加const的实质区别是什么。在用非const的指针，引用和值均可转化为const的。这一点没有太多可说明的东东。
对于函数值传递的情况，因为参数传递是通过复制实参创建一个临时变量传递进函数的，函数内只能改变临时变量，但无法改变实参。则这个时候无论加不加 const对实参不会产生任何影响。但是在引用或指针传递函数调用中，因为传进去的是一个引用或指针，这样函数内部可以改变引用或指针所指向的变量，这时 const 才是实实在在地保护了实参所指向的变量。因为在编译阶段编译器对调用函数的选择是根据实参进行的，所以，只有引用传递和指针传递可以用是否加const来 重载。
下面给出一个例子可能就更明白了：
- #include<iostream>
- class A{
- public:
- A();
- int foo(int *test);
- int foo(const int *test);
- };
- A::A(){
- }
- int A::foo(int *test){
- std::cout << *test << " A::foo(int *test)" <<std::endl;
- return 1;
- }
- int A::foo(const int *test){
- std::cout << *test << " A::foo(const int *test)" <<std::endl;
- return 1;
- }
- int main()
- {
- const int b =5;
- int c = 3;
- A a;
- a.foo(&b);
- a.foo(&c);
- return 1;
- }
输出：
A::foo(const int *test)
A::foo(int *test)
那么编译器又是怎样工作的，通过g++ -S选项将汇编代码生成出来，通过AT&T汇编代码可以看出一些端倪来（之所以用AT&T汇编是因为VS生成的中间代码实在是让人头晕）：
.file "overload.cpp"
.section .ctors,"aw",@progbits
.align 4
.long _GLOBAL__I__ZN1AC2Ev
.text
.align 2
.globl _ZN1AC2Ev
.type _ZN1AC2Ev, @function
_ZN1AC2Ev:
.LFB1399:
pushl %ebp
.LCFI0:
movl %esp, %ebp
.LCFI1:
popl %ebp
ret
.LFE1399:
.size _ZN1AC2Ev, .-_ZN1AC2Ev
.globl __gxx_personality_v0
.align 2
.globl _ZN1AC1Ev
.type _ZN1AC1Ev, @function
_ZN1AC1Ev:
.LFB1400:
pushl %ebp
.LCFI2:
movl %esp, %ebp
.LCFI3:
popl %ebp
ret
.LFE1400:
.size _ZN1AC1Ev, .-_ZN1AC1Ev
.align 2
.type _Z41__static_initialization_and_destruction_0ii, @function
_Z41__static_initialization_and_destruction_0ii:
.LFB1411:
pushl %ebp
.LCFI4:
movl %esp, %ebp
.LCFI5:
subl $24, %esp
.LCFI6:
movl %eax, -4(%ebp)
movl %edx, -8(%ebp)
cmpl $1, -4(%ebp)
jne .L9
cmpl $65535, -8(%ebp)
jne .L9
movl $_ZSt8__ioinit, (%esp)
call _ZNSt8ios_base4InitC1Ev
movl $__dso_handle, 8(%esp)
movl $0, 4(%esp)
movl $__tcf_0, (%esp)
call __cxa_atexit
.L9:
leave
ret
.LFE1411:
.size _Z41__static_initialization_and_destruction_0ii, .-_Z41__static_initialization_and_destruction_0ii
.align 2
.type _GLOBAL__I__ZN1AC2Ev, @function
_GLOBAL__I__ZN1AC2Ev:
.LFB1413:
pushl %ebp
.LCFI7:
movl %esp, %ebp
.LCFI8:
subl $8, %esp
.LCFI9:
movl $65535, %edx
movl $1, %eax
call _Z41__static_initialization_and_destruction_0ii
leave
ret
.LFE1413:
.size _GLOBAL__I__ZN1AC2Ev, .-_GLOBAL__I__ZN1AC2Ev
.align 2
.type __tcf_0, @function
__tcf_0:
.LFB1412:
pushl %ebp
.LCFI10:
movl %esp, %ebp
.LCFI11:
subl $8, %esp
.LCFI12:
movl $_ZSt8__ioinit, (%esp)
call _ZNSt8ios_base4InitD1Ev
leave
ret
.LFE1412:
.size __tcf_0, .-__tcf_0
.section .rodata
.LC0:
.string " A::foo(const int *test)"
.text
.align 2
.globl _ZN1A3fooEPKi
.type _ZN1A3fooEPKi, @function
_ZN1A3fooEPKi:
.LFB1402:
pushl %ebp
.LCFI13:
movl %esp, %ebp
.LCFI14:
subl $8, %esp
.LCFI15:
movl 12(%ebp), %eax
movl (%eax), %eax
movl %eax, 4(%esp)
movl $_ZSt4cout, (%esp)
call _ZNSolsEi
movl $.LC0, 4(%esp)
movl %eax, (%esp)
call _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
movl $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, 4(%esp)
movl %eax, (%esp)
call _ZNSolsEPFRSoS_E
movl $1, %eax
leave
ret
.LFE1402:
.size _ZN1A3fooEPKi, .-_ZN1A3fooEPKi
.section .rodata
.LC1:
.string " A::foo(int *test)"
.text
.align 2
.globl _ZN1A3fooEPi
.type _ZN1A3fooEPi, @function
_ZN1A3fooEPi:
.LFB1401:
pushl %ebp
.LCFI16:
movl %esp, %ebp
.LCFI17:
subl $8, %esp
.LCFI18:
movl 12(%ebp), %eax
movl (%eax), %eax
movl %eax, 4(%esp)
movl $_ZSt4cout, (%esp)
call _ZNSolsEi
movl $.LC1, 4(%esp)
movl %eax, (%esp)
call _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
movl $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, 4(%esp)
movl %eax, (%esp)
call _ZNSolsEPFRSoS_E
movl $1, %eax
leave
ret
.LFE1401:
.size _ZN1A3fooEPi, .-_ZN1A3fooEPi
.align 2
.globl main
.type main, @function
main:
.LFB1403:
leal 4(%esp), %ecx
.LCFI19:
andl $-16, %esp
pushl -4(%ecx)
.LCFI20:
pushl %ebp
.LCFI21:
movl %esp, %ebp
.LCFI22:
pushl %ecx
.LCFI23:
subl $36, %esp
.LCFI24:
movl $5, -8(%ebp)
movl $3, -12(%ebp)
leal -13(%ebp), %eax
movl %eax, (%esp)
call _ZN1AC1Ev
leal -8(%ebp), %eax
movl %eax, 4(%esp)
leal -13(%ebp), %eax
movl %eax, (%esp)
call _ZN1A3fooEPKi
leal -12(%ebp), %eax
movl %eax, 4(%esp)
leal -13(%ebp), %eax
movl %eax, (%esp)
call _ZN1A3fooEPi
movl $1, %eax
addl $36, %esp
popl %ecx
popl %ebp
leal -4(%ecx), %esp
ret
.LFE1403:
.size main, .-main
.local _ZSt8__ioinit
.comm _ZSt8__ioinit,1,1
.weakref _Z20__gthrw_pthread_oncePiPFvvE,pthread_once
.weakref _Z27__gthrw_pthread_getspecificj,pthread_getspecific
.weakref _Z27__gthrw_pthread_setspecificjPKv,pthread_setspecific
.weakref _Z22__gthrw_pthread_createPmPK14pthread_attr_tPFPvS3_ES3_,pthread_create
.weakref _Z22__gthrw_pthread_cancelm,pthread_cancel
.weakref _Z26__gthrw_pthread_mutex_lockP15pthread_mutex_t,pthread_mutex_lock
.weakref _Z29__gthrw_pthread_mutex_trylockP15pthread_mutex_t,pthread_mutex_trylock
.weakref _Z28__gthrw_pthread_mutex_unlockP15pthread_mutex_t,pthread_mutex_unlock
.weakref _Z26__gthrw_pthread_mutex_initP15pthread_mutex_tPK19pthread_mutexattr_t,pthread_mutex_init
.weakref _Z26__gthrw_pthread_key_createPjPFvPvE,pthread_key_create
.weakref _Z26__gthrw_pthread_key_deletej,pthread_key_delete
.weakref _Z30__gthrw_pthread_mutexattr_initP19pthread_mutexattr_t,pthread_mutexattr_init
.weakref _Z33__gthrw_pthread_mutexattr_settypeP19pthread_mutexattr_ti,pthread_mutexattr_settype
.weakref _Z33__gthrw_pthread_mutexattr_destroyP19pthread_mutexattr_t,pthread_mutexattr_destroy
.section .eh_frame,"a",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0x0
.byte 0x1
.string "zP"
.uleb128 0x1
.sleb128 -4
.byte 0x8
.uleb128 0x5
.byte 0x0
.long __gxx_personality_v0
.byte 0xc
.uleb128 0x4
.uleb128 0x4
.byte 0x88
.uleb128 0x1
.align 4
.LECIE1:
.LSFDE5:
.long .LEFDE5-.LASFDE5
.LASFDE5:
.long .LASFDE5-.Lframe1
.long .LFB1411
.long .LFE1411-.LFB1411
.uleb128 0x0
.byte 0x4
.long .LCFI4-.LFB1411
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI5-.LCFI4
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE5:
.LSFDE7:
.long .LEFDE7-.LASFDE7
.LASFDE7:
.long .LASFDE7-.Lframe1
.long .LFB1413
.long .LFE1413-.LFB1413
.uleb128 0x0
.byte 0x4
.long .LCFI7-.LFB1413
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI8-.LCFI7
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE7:
.LSFDE9:
.long .LEFDE9-.LASFDE9
.LASFDE9:
.long .LASFDE9-.Lframe1
.long .LFB1412
.long .LFE1412-.LFB1412
.uleb128 0x0
.byte 0x4
.long .LCFI10-.LFB1412
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI11-.LCFI10
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE9:
.LSFDE11:
.long .LEFDE11-.LASFDE11
.LASFDE11:
.long .LASFDE11-.Lframe1
.long .LFB1402
.long .LFE1402-.LFB1402
.uleb128 0x0
.byte 0x4
.long .LCFI13-.LFB1402
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI14-.LCFI13
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE11:
.LSFDE13:
.long .LEFDE13-.LASFDE13
.LASFDE13:
.long .LASFDE13-.Lframe1
.long .LFB1401
.long .LFE1401-.LFB1401
.uleb128 0x0
.byte 0x4
.long .LCFI16-.LFB1401
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI17-.LCFI16
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE13:
.LSFDE15:
.long .LEFDE15-.LASFDE15
.LASFDE15:
.long .LASFDE15-.Lframe1
.long .LFB1403
.long .LFE1403-.LFB1403
.uleb128 0x0
.byte 0x4
.long .LCFI19-.LFB1403
.byte 0xc
.uleb128 0x1
.uleb128 0x0
.byte 0x9
.uleb128 0x4
.uleb128 0x1
.byte 0x4
.long .LCFI20-.LCFI19
.byte 0xc
.uleb128 0x4
.uleb128 0x4
.byte 0x4
.long .LCFI21-.LCFI20
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI22-.LCFI21
.byte 0xd
.uleb128 0x5
.byte 0x4
.long .LCFI23-.LCFI22
.byte 0x84
.uleb128 0x3
.align 4
.LEFDE15:
.ident "GCC: (GNU) 4.1.2 20070925 (Red Hat 4.1.2-33)"
.section .note.GNU-stack,"",@progbits
如上面的代码函数：
int foo(int *test);和int foo(const int *test);
分别被编译器生成名为：_ZN1A3fooEPKi和_ZN1A3fooEPi（这两个名字会因为编译器的不同而不同，名字只是一个区分的 符号而已不用深究，只用知道重载的函数经过编译器的处理函数名字已经发生了变化。所以对于后面的汇编和链接工作就不存在重载的问题了。）这里也同时说明对 重载来说在编译阶段已经完成。
对于a.foo(&b);因为变量b有const修饰所以就调用了int foo(const int *test);对于a.foo(&c);调用int foo(int *test);因为这个是精确匹配的。但是如果没有定义int foo(const int *test);则在代码24行会出现编译错误。反过来如果没有定义函数：int foo(int *test)；如下：
- #include<iostream>
- class A{
- public:
- A();
- // int foo(int *test);
- int foo(const int *test);
- };
- A::A(){
- }
- /*int A::foo(int *test){
- std::cout << *test << " A::foo(int *test)" <<std::endl;
- return 1;
- }
- */
- int A::foo(const int *test){
- std::cout << *test << " A::foo(const int *test)" <<std::endl;
- return 1;
- }
- int main()
- {
- const int b =5;
- int c = 3;
- A a;
- a.foo(&b);
- a.foo(&c);
- return 1;
- }
则输出结果为：
5 A::foo(const int *test)
3 A::foo(const int *test)
原因c++ primer上讲的很清楚：“We can use a nonconst object to initializer either aconst or nonconst reference. However, initializing aconst reference to a nonconst object requires a conversion, whereas initializing a nonconst parameter is an exact match.”
const 成员函数重载的解析：
const 成员函数重载的解析和const参数重载解析的原理可以说是一样的。之所以这样说是因为const成员函数的解析可被看做是对函数this参数用const来修饰的过程。例如下面代码：
- #include<iostream>
- class A{
- public:
- A();
- int foo(int *test); //可看做：int foo(A *this,int *test);
- int foo(int *test) const;//可看做：int foo(const A *this,int *test);
- };
- A::A(){
- }
- int A::foo(int *test){
- std::cout << *test << "foo" <<std::endl;
- return 1;
- }
- int A::foo(int *test) const {
- std::cout << *test << "foo const" <<std::endl;
- return 1;
- }
- int main()
- {
- int b = 5;
- const A a;
- a.foo(&b);
- return 1;
- }
生成汇编为：
.file "overload1.cpp"
.section .ctors,"aw",@progbits
.align 4
.long _GLOBAL__I__ZN1AC2Ev
.text
.align 2
.globl _ZN1AC2Ev
.type _ZN1AC2Ev, @function
_ZN1AC2Ev:
.LFB1399:
pushl %ebp
.LCFI0:
movl %esp, %ebp
.LCFI1:
popl %ebp
ret
.LFE1399:
.size _ZN1AC2Ev, .-_ZN1AC2Ev
.globl __gxx_personality_v0
.align 2
.globl _ZN1AC1Ev
.type _ZN1AC1Ev, @function
_ZN1AC1Ev:
.LFB1400:
pushl %ebp
.LCFI2:
movl %esp, %ebp
.LCFI3:
popl %ebp
ret
.LFE1400:
.size _ZN1AC1Ev, .-_ZN1AC1Ev
.align 2
.type _Z41__static_initialization_and_destruction_0ii, @function
_Z41__static_initialization_and_destruction_0ii:
.LFB1411:
pushl %ebp
.LCFI4:
movl %esp, %ebp
.LCFI5:
subl $24, %esp
.LCFI6:
movl %eax, -4(%ebp)
movl %edx, -8(%ebp)
cmpl $1, -4(%ebp)
jne .L9
cmpl $65535, -8(%ebp)
jne .L9
movl $_ZSt8__ioinit, (%esp)
call _ZNSt8ios_base4InitC1Ev
movl $__dso_handle, 8(%esp)
movl $0, 4(%esp)
movl $__tcf_0, (%esp)
call __cxa_atexit
.L9:
leave
ret
.LFE1411:
.size _Z41__static_initialization_and_destruction_0ii, .-_Z41__static_initialization_and_destruction_0ii
.align 2
.type _GLOBAL__I__ZN1AC2Ev, @function
_GLOBAL__I__ZN1AC2Ev:
.LFB1413:
pushl %ebp
.LCFI7:
movl %esp, %ebp
.LCFI8:
subl $8, %esp
.LCFI9:
movl $65535, %edx
movl $1, %eax
call _Z41__static_initialization_and_destruction_0ii
leave
ret
.LFE1413:
.size _GLOBAL__I__ZN1AC2Ev, .-_GLOBAL__I__ZN1AC2Ev
.align 2
.type __tcf_0, @function
__tcf_0:
.LFB1412:
pushl %ebp
.LCFI10:
movl %esp, %ebp
.LCFI11:
subl $8, %esp
.LCFI12:
movl $_ZSt8__ioinit, (%esp)
call _ZNSt8ios_base4InitD1Ev
leave
ret
.LFE1412:
.size __tcf_0, .-__tcf_0
.section .rodata
.LC0:
.string "foo const"
.text
.align 2
.globl _ZNK1A3fooEPi
.type _ZNK1A3fooEPi, @function
_ZNK1A3fooEPi:
.LFB1402:
pushl %ebp
.LCFI13:
movl %esp, %ebp
.LCFI14:
subl $8, %esp
.LCFI15:
movl 12(%ebp), %eax
movl (%eax), %eax
movl %eax, 4(%esp)
movl $_ZSt4cout, (%esp)
call _ZNSolsEi
movl $.LC0, 4(%esp)
movl %eax, (%esp)
call _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
movl $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, 4(%esp)
movl %eax, (%esp)
call _ZNSolsEPFRSoS_E
movl $1, %eax
leave
ret
.LFE1402:
.size _ZNK1A3fooEPi, .-_ZNK1A3fooEPi
.align 2
.globl main
.type main, @function
main:
.LFB1403:
leal 4(%esp), %ecx
.LCFI16:
andl $-16, %esp
pushl -4(%ecx)
.LCFI17:
pushl %ebp
.LCFI18:
movl %esp, %ebp
.LCFI19:
pushl %ecx
.LCFI20:
subl $36, %esp
.LCFI21:
movl $5, -8(%ebp)
leal -9(%ebp), %eax
movl %eax, (%esp)
call _ZN1AC1Ev
leal -8(%ebp), %eax
movl %eax, 4(%esp)
leal -9(%ebp), %eax
movl %eax, (%esp)
call _ZNK1A3fooEPi
movl $1, %eax
addl $36, %esp
popl %ecx
popl %ebp
leal -4(%ecx), %esp
ret
.LFE1403:
.size main, .-main
.section .rodata
.LC1:
.string "foo"
.text
.align 2
.globl _ZN1A3fooEPi
.type _ZN1A3fooEPi, @function
_ZN1A3fooEPi:
.LFB1401:
pushl %ebp
.LCFI22:
movl %esp, %ebp
.LCFI23:
subl $8, %esp
.LCFI24:
movl 12(%ebp), %eax
movl (%eax), %eax
movl %eax, 4(%esp)
movl $_ZSt4cout, (%esp)
call _ZNSolsEi
movl $.LC1, 4(%esp)
movl %eax, (%esp)
call _ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
movl $_ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, 4(%esp)
movl %eax, (%esp)
call _ZNSolsEPFRSoS_E
movl $1, %eax
leave
ret
.LFE1401:
.size _ZN1A3fooEPi, .-_ZN1A3fooEPi
.local _ZSt8__ioinit
.comm _ZSt8__ioinit,1,1
.weakref _Z20__gthrw_pthread_oncePiPFvvE,pthread_once
.weakref _Z27__gthrw_pthread_getspecificj,pthread_getspecific
.weakref _Z27__gthrw_pthread_setspecificjPKv,pthread_setspecific
.weakref _Z22__gthrw_pthread_createPmPK14pthread_attr_tPFPvS3_ES3_,pthread_create
.weakref _Z22__gthrw_pthread_cancelm,pthread_cancel
.weakref _Z26__gthrw_pthread_mutex_lockP15pthread_mutex_t,pthread_mutex_lock
.weakref _Z29__gthrw_pthread_mutex_trylockP15pthread_mutex_t,pthread_mutex_trylock
.weakref _Z28__gthrw_pthread_mutex_unlockP15pthread_mutex_t,pthread_mutex_unlock
.weakref _Z26__gthrw_pthread_mutex_initP15pthread_mutex_tPK19pthread_mutexattr_t,pthread_mutex_init
.weakref _Z26__gthrw_pthread_key_createPjPFvPvE,pthread_key_create
.weakref _Z26__gthrw_pthread_key_deletej,pthread_key_delete
.weakref _Z30__gthrw_pthread_mutexattr_initP19pthread_mutexattr_t,pthread_mutexattr_init
.weakref _Z33__gthrw_pthread_mutexattr_settypeP19pthread_mutexattr_ti,pthread_mutexattr_settype
.weakref _Z33__gthrw_pthread_mutexattr_destroyP19pthread_mutexattr_t,pthread_mutexattr_destroy
.section .eh_frame,"a",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0x0
.byte 0x1
.string "zP"
.uleb128 0x1
.sleb128 -4
.byte 0x8
.uleb128 0x5
.byte 0x0
.long __gxx_personality_v0
.byte 0xc
.uleb128 0x4
.uleb128 0x4
.byte 0x88
.uleb128 0x1
.align 4
.LECIE1:
.LSFDE5:
.long .LEFDE5-.LASFDE5
.LASFDE5:
.long .LASFDE5-.Lframe1
.long .LFB1411
.long .LFE1411-.LFB1411
.uleb128 0x0
.byte 0x4
.long .LCFI4-.LFB1411
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI5-.LCFI4
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE5:
.LSFDE7:
.long .LEFDE7-.LASFDE7
.LASFDE7:
.long .LASFDE7-.Lframe1
.long .LFB1413
.long .LFE1413-.LFB1413
.uleb128 0x0
.byte 0x4
.long .LCFI7-.LFB1413
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI8-.LCFI7
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE7:
.LSFDE9:
.long .LEFDE9-.LASFDE9
.LASFDE9:
.long .LASFDE9-.Lframe1
.long .LFB1412
.long .LFE1412-.LFB1412
.uleb128 0x0
.byte 0x4
.long .LCFI10-.LFB1412
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI11-.LCFI10
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE9:
.LSFDE11:
.long .LEFDE11-.LASFDE11
.LASFDE11:
.long .LASFDE11-.Lframe1
.long .LFB1402
.long .LFE1402-.LFB1402
.uleb128 0x0
.byte 0x4
.long .LCFI13-.LFB1402
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI14-.LCFI13
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE11:
.LSFDE13:
.long .LEFDE13-.LASFDE13
.LASFDE13:
.long .LASFDE13-.Lframe1
.long .LFB1403
.long .LFE1403-.LFB1403
.uleb128 0x0
.byte 0x4
.long .LCFI16-.LFB1403
.byte 0xc
.uleb128 0x1
.uleb128 0x0
.byte 0x9
.uleb128 0x4
.uleb128 0x1
.byte 0x4
.long .LCFI17-.LCFI16
.byte 0xc
.uleb128 0x4
.uleb128 0x4
.byte 0x4
.long .LCFI18-.LCFI17
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI19-.LCFI18
.byte 0xd
.uleb128 0x5
.byte 0x4
.long .LCFI20-.LCFI19
.byte 0x84
.uleb128 0x3
.align 4
.LEFDE13:
.LSFDE15:
.long .LEFDE15-.LASFDE15
.LASFDE15:
.long .LASFDE15-.Lframe1
.long .LFB1401
.long .LFE1401-.LFB1401
.uleb128 0x0
.byte 0x4
.long .LCFI22-.LFB1401
.byte 0xe
.uleb128 0x8
.byte 0x85
.uleb128 0x2
.byte 0x4
.long .LCFI23-.LCFI22
.byte 0xd
.uleb128 0x5
.align 4
.LEFDE15:
.ident "GCC: (GNU) 4.1.2 20070925 (Red Hat 4.1.2-33)"
.section .note.GNU-stack,"",@progbits
上面可以看到编译阶段的调用也是通过对重载函数的别名来实现的。
总结：
1.const重载主要是通过能否对传入的参数进行修改为判断的。
2.const参数重载和const函数重载机制都是一样的，因为对于const 函数重载可看做是对隐含的指针this的参数重载。
3.重载是在编译阶段已经完成，对于汇编和链接来说透明的。
文章转载自：罗索实验室 [http://www.rosoo.net/a/201203/15893.html]
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