如何查看类似strcpy这样的函数的内部实现

[minioreo]

如题

[liecs]

linux内核源码
可以 code.google.com 之
不同的系统实现的方式也是不同的

[minioreo]

哦 windows平台呢？想看一些C库函数的实现

[minioreo]

多谢4楼 我看到汇编代码了 你的C源码是在哪看到的？还是从汇编反向工程出来的？
我在C:\Program Files\Microsoft Visual Studio 9.0\VC\crt\src里只能找到strcat的定义

[R9R9R9]

查看方法：

在调试状态下，在即将执行到strcpy的时候，按f11进入函数体内部，就能看到！

就在汇编代码的上面几行。向上向上

[R9R9R9]

其实就是那些汇编代码的注释。

[LogWarning]

VC的crt实现在：Microsoft Visual Studio/VC/crt/src/

[太乙]

page
;***
;char *strcpy(dst, src) - copy one string over another
;
;Purpose:
;       Copies the string src into the spot specified by
;       dest; assumes enough room.
;
;       Algorithm:
;       char * strcpy (char * dst, char * src)
;       {
;           char * cp = dst;
;
;           while( *cp++ = *src++ )
;                   ;               /* Copy src over dst */
;           return( dst );
;       }
;
;Entry:
;       char * dst - string over which "src" is to be copied
;       const char * src - string to be copied over "dst"
;
;Exit:
;       The address of "dst" in EAX
;
;Uses:
;       EAX, ECX
;
;Exceptions:
;*******************************************************************************


        CODESEG

%       public  strcat, strcpy      ; make both functions available
strcpy  proc
        push    edi                 ; preserve edi
        mov     edi,[esp+8]         ; edi points to dest string
        jmp     short copy_start

strcpy  endp

        align   16

strcat  proc

        .FPO    ( 0, 2, 0, 0, 0, 0 )

        mov     ecx,[esp+4]         ; ecx -> dest string
        push    edi                 ; preserve edi
        test    ecx,3               ; test if string is aligned on 32 bits
        je      short find_end_of_dest_string_loop

dest_misaligned:                    ; simple byte loop until string is aligned
        mov     al,byte ptr [ecx]
        inc     ecx
        test    al,al
        je      short start_byte_3
        test    ecx,3
        jne     short dest_misaligned

        align   4

find_end_of_dest_string_loop:
        mov     eax,dword ptr [ecx] ; read 4 bytes
        mov     edx,7efefeffh
        add     edx,eax
        xor     eax,-1
        xor     eax,edx
        add     ecx,4
        test    eax,81010100h
        je      short find_end_of_dest_string_loop
        ; found zero byte in the loop
        mov     eax,[ecx - 4]
        test    al,al               ; is it byte 0
        je      short start_byte_0
        test    ah,ah               ; is it byte 1
        je      short start_byte_1
        test    eax,00ff0000h       ; is it byte 2
        je      short start_byte_2
        test    eax,0ff000000h      ; is it byte 3
        je      short start_byte_3
        jmp     short find_end_of_dest_string_loop
                                    ; taken if bits 24-30 are clear and bit
                                    ; 31 is set
start_byte_3:
        lea     edi,[ecx - 1]
        jmp     short copy_start
start_byte_2:
        lea     edi,[ecx - 2]
        jmp     short copy_start
start_byte_1:
        lea     edi,[ecx - 3]
        jmp     short copy_start
start_byte_0:
        lea     edi,[ecx - 4]
;       jmp     short copy_start

;       edi points to the end of dest string.
copy_start::
        mov     ecx,[esp+0ch]       ; ecx -> sorc string
        test    ecx,3               ; test if string is aligned on 32 bits
        je      short main_loop_entrance

src_misaligned:                     ; simple byte loop until string is aligned
        mov     dl,byte ptr [ecx]
        inc     ecx
        test    dl,dl
        je      short byte_0
        mov     [edi],dl
        inc     edi
        test    ecx,3
        jne     short src_misaligned
        jmp     short main_loop_entrance

main_loop:                          ; edx contains first dword of sorc string
        mov     [edi],edx           ; store one more dword
        add     edi,4               ; kick dest pointer
main_loop_entrance:
        mov     edx,7efefeffh
        mov     eax,dword ptr [ecx] ; read 4 bytes

        add     edx,eax
        xor     eax,-1

        xor     eax,edx
        mov     edx,[ecx]           ; it's in cache now

        add     ecx,4               ; kick dest pointer
        test    eax,81010100h

        je      short main_loop
        ; found zero byte in the loop
; main_loop_end:
        test    dl,dl               ; is it byte 0
        je      short byte_0
        test    dh,dh               ; is it byte 1
        je      short byte_1
        test    edx,00ff0000h       ; is it byte 2
        je      short byte_2
        test    edx,0ff000000h      ; is it byte 3
        je      short byte_3
        jmp     short main_loop     ; taken if bits 24-30 are clear and bit
                                    ; 31 is set
byte_3:
        mov     [edi],edx
        mov     eax,[esp+8]         ; return in eax pointer to dest string
        pop     edi
        ret
byte_2:
        mov     [edi],dx
        mov     eax,[esp+8]         ; return in eax pointer to dest string
        mov     byte ptr [edi+2],0
        pop     edi
        ret
byte_1:
        mov     [edi],dx
        mov     eax,[esp+8]         ; return in eax pointer to dest string
        pop     edi
        ret
byte_0:
        mov     [edi],dl
        mov     eax,[esp+8]         ; return in eax pointer to dest string
        pop     edi
        ret

strcat  endp

        end






查看方法：

在vc6.0的调试状态下，在即将执行到strcpy的时候，按f11进入函数体内部，就能看到！

[jkjackstar]

到底怎么弄啊？ 有没有完整的？