Const 重載解析

總結：1.const重載主要是通過能否對傳入的參數進行修改為判斷的。2.const參數重載和const函數重載機制都是一樣的，因為對于const 函數重載可看做是對隐含的指針this的參數重載。3.重載是在編譯階段已經完成，對于彙編和連結來說透明的。

TAG: 彙編 const 重載

書上和網上在很多地方都對const 的重載做了一些解釋，但感覺都不是很詳細。還有很多同學在不同的地方發問關于const 重載的問題，這裡我又重新看了一下，做了一個簡單的分析也可能有不對的地方，歡迎讨論。

所謂重載，是指允許存在多個同名函數，而這些函數的參數表不同，即函數名相同但函數的簽名不同。重載并不是面向對象程式設計的特有屬性，這是因為重載是在編譯階段實作的，編譯器根據函數不同的參數表，對同名函數的名稱做修飾，然後這些同名函數就成了不同的函數（這一點稍後有例子）。了

Const 參數重載解析：

關于const 重載幾乎在所有c++的書中者提到過但大部分隻是一句話，例如在《C++ primer》一書中這樣描述：“可基于函數的引用形參是指向 const 對象還是指向非 const 對象，實作函數重載。将引用形參定義為 const 來重載函數是合法的，因為編譯器可以根據實參是否為 const 确定調用哪一個函數。”

但是這一段描述并沒有給出引用、指針和值傳遞前加const的實質差別是什麼。在用非const的指針，引用和值均可轉化為const的。這一點沒有太多可說明的東東。

對于函數值傳遞的情況，因為參數傳遞是通過複制實參建立一個臨時變量傳遞進函數的，函數内隻能改變臨時變量，但無法改變實參。則這個時候無論加不加 const對實參不會産生任何影響。但是在引用或指針傳遞函數調用中，因為傳進去的是一個引用或指針，這樣函數内部可以改變引用或指針所指向的變量，這時 const 才是實實在在地保護了實參所指向的變量。因為在編譯階段編譯器對調用函數的選擇是根據實參進行的，是以，隻有引用傳遞和指針傳遞可以用是否加const來重載。

下面給出一個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;       
       }

輸出：

A::foo(const int *test)

A::foo(int *test)

那麼編譯器又是怎樣工作的，通過g++ -S選項将彙編代碼生成出來，通過AT&T彙編代碼可以看出一些端倪來（之是以用AT&T彙編是因為VS生成的中間代碼實在是讓人頭暈）：

.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

.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

.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

如上面的代碼函數：

int foo(int *test);和int foo(const int *test);

分别被編譯器生成名為：_ZN1A3fooEPKi和_ZN1A3fooEPi（這兩個名字會因為編譯器的不同而不同，名字隻是一個區分的符号而已不用深究，隻用知道重載的函數經過編譯器的處理函數名字已經發生了變化。是以對于後面的彙編和連結工作就不存在重載的問題了。）這裡也同時說明對重載來說在編譯階段已經完成。

對于a.foo(&b);因為變量b有const修飾是以就調用了int foo(const int *test);對于a.foo(&c);調用int foo(int *test);因為這個是精确比對的。但是如果沒有定義int foo(const int *test);則在代碼24行會出現編譯錯誤。反過來如果沒有定義函數：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;       
       }

則輸出結果為：

5 A::foo(const int *test)

3 A::foo(const int *test)

原因c++ primer上講的很清楚：“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 成員函數重載的解析：

const 成員函數重載的解析和const參數重載解析的原理可以說是一樣的。之是以這樣說是因為const成員函數的解析可被看做是對函數this參數用const來修飾的過程。例如下面代碼：

  #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;       
       }

生成彙編為：

.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

.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

.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

上面可以看到編譯階段的調用也是通過對重載函數的别名來實作的。

總結：

1.const重載主要是通過能否對傳入的參數進行修改為判斷的。

2.const參數重載和const函數重載機制都是一樣的，因為對于const 函數重載可看做是對隐含的指針this的參數重載。

3.重載是在編譯階段已經完成，對于彙編和連結來說透明的。

文章轉載自：羅索實驗室 [http://www.rosoo.net/a/201203/15893.html]

Const 重載解析

繼續閱讀

c++ 比對相鄰元素相等的元素（adjacent_find）

DateTimePicker 控件的格式設定

swmm與lisflood-fp源碼如何一起編譯 CMake指令

Windows下VS開發環境環境安裝工程項目設定關于Debug和Release的提示

一文看懂字元串的加減乘除

C++ 第十五周報告1--《冒泡法排序》

C++數組引用C++數組引用

C++實作簡單順序表

[C++學習曆程]基礎部分 C++中的函數學習

C經典書籍筆記——C陷阱與缺陷②(文法陷阱之優先級)一、錯誤案列二、優先級規律

使用遞減運算符在循環中按遞減順序列印10到0之間的整數

指針，常量和類型别名

VS C++常見問題集錦1.在Vs中編C出現這兩個錯誤是什麼原因？錯誤1：error LNK2005: _main 已經在 *** 中定義

線性表之順序表的實作

C++判斷素數、求最大公約數代碼判斷一個數是否為素數求兩個數的最大公約數

SequoiaDB巨杉資料庫C++驅動概述