user-0 提问: 字符串查找并返回问题，谢谢

回复:
user: user-1
content: lz没看见 if？？？？

user: user-0
content: 您好，问您一个问题，这里有两个return,第一个如果执行了，第二个还会返回吗？ 引用 2 楼 zhao4zhong1 的回复:C:\Program Files\Microsoft Visual Studio\VC98\CRT\SRC\STRCHR.C /*** *strchr.c - search a string for a given character * *       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved. * *Purpose: *       defines strchr() - search a string for a character * *******************************************************************************/  #include <cruntime.h> #include <string.h>  /*** *char *strchr(string, c) - search a string for a character * *Purpose: *       Searches a string for a given character, which may be the *       null character '\0'. * *Entry: *       char *string - string to search in *       char c - character to search for * *Exit: *       returns pointer to the first occurence of c in string *       returns NULL if c does not occur in string * *Exceptions: * *******************************************************************************/  char * __cdecl strchr (         const char * string,         int ch         ) {         while (*string && *string != (char)ch)                 string++;          if (*string == (char)ch)                 return((char *)string);         return(NULL); }

user: user-2
content: C:\Program Files\Microsoft Visual Studio\VC98\CRT\SRC\STRCHR.C /*** *strchr.c - search a string for a given character * *       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved. * *Purpose: *       defines strchr() - search a string for a character * *******************************************************************************/  #include <cruntime.h> #include <string.h>  /*** *char *strchr(string, c) - search a string for a character * *Purpose: *       Searches a string for a given character, which may be the *       null character '\0'. * *Entry: *       char *string - string to search in *       char c - character to search for * *Exit: *       returns pointer to the first occurence of c in string *       returns NULL if c does not occur in string * *Exceptions: * *******************************************************************************/  char * __cdecl strchr (         const char * string,         int ch         ) {         while (*string && *string != (char)ch)                 string++;          if (*string == (char)ch)                 return((char *)string);         return(NULL); }

user: user-0
content: *ret++;注释掉了，忘记打了，谢谢

user: user-2
content: C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\intel\strchr.asm 		page	,132 		title	strchr - search	string for given character ;*** ;strchr.asm	- search a string for a	given character ; ;		Copyright (c) Microsoft	Corporation. All rights	reserved. ; ;Purpose: ;		defines	strchr() - search a	string for a character ; ;*******************************************************************************  		.xlist 		include	cruntime.inc 		.list  page ;*** ;char *strchr(string, chr) - search	a string for a character ; ;Purpose: ;		Searches a string for a	given character, which may be the ;		null character '\0'. ; ;		Algorithm: ;		char * ;		strchr (string,	chr) ;		char *string, chr; ;		{ ;		  while	(*string &&	*string	!= chr) ;			  string++; ;		  if (*string == chr) ;			  return(string); ;		  return((char *)0); ;		} ; ;Entry: ;		char *string - string to search	in ;		char chr	 - character to	search for ; ;Exit: ;		returns	pointer	to the first occurence of c	in string ;		returns	NULL if	chr	does not occur in string ; ;Uses: ; ;Exceptions: ; ;*******************************************************************************  		CODESEG  found_bx: 		lea		eax,[edx - 1] 		pop		ebx					; restore ebx 		ret							; _cdecl return  		align	16 		public	strchr,	__from_strstr_to_strchr strchr	proc \ 		string:ptr byte, \ 		chr:byte  		OPTION PROLOGUE:NONE, EPILOGUE:NONE  		.FPO	( 0, 2,	0, 0, 0, 0 )  		xor		eax,eax 		mov		al,[esp	+ 8]		; al = chr (search char)  __from_strstr_to_strchr	label proc  		push	ebx					; PRESERVE EBX 		mov		ebx,eax				; ebx =	0/0/0/chr 		shl		eax,8				; eax =	0/0/chr/0 		mov		edx,[esp + 8]		; edx =	buffer 		test	edx,3				; test if string is	aligned	on 32 bits 		jz		short main_loop_start  str_misaligned:						; simple byte loop until string	is aligned 		mov		cl,[edx] 		add		edx,1 		cmp		cl,bl 		je		short found_bx 		test	cl,cl 		jz		short retnull_bx 		test	edx,3				; now aligned ? 		jne		short str_misaligned  main_loop_start:					; set all 4	bytes of ebx to	[chr] 		or		ebx,eax				; ebx =	0/0/chr/chr 		push	edi					; PRESERVE EDI 		mov		eax,ebx				; eax =	0/0/chr/chr 		shl		ebx,10h				; ebx =	chr/chr/0/0 		push	esi					; PRESERVE ESI 		or		ebx,eax				; ebx =	all	4 bytes	= [chr]  ; in the main loop (below),	we are looking for chr or for EOS (end of string)  main_loop: 		mov		ecx,[edx]			; read	dword (4 bytes) 		mov		edi,7efefeffh		; work with	edi	& ecx for looking for chr  		mov		eax,ecx				; eax =	dword 		mov		esi,edi				; work with	esi	& eax for looking for EOS  		xor		ecx,ebx				; eax =	dword xor chr/chr/chr/chr 		add		esi,eax  		add		edi,ecx 		xor		ecx,-1  		xor		eax,-1 		xor		ecx,edi  		xor		eax,esi 		add		edx,4  		and		ecx,81010100h		; test for chr 		jnz		short chr_is_found	; chr probably has been	found  		; chr was not found, check for EOS  		and		eax,81010100h		; is any flag set ?? 		jz		short main_loop		; EOS was not found, go	get	another	dword  		and		eax,01010100h		; is it	in high	byte? 		jnz		short retnull		; no, definitely found EOS,	return failure  		and		esi,80000000h		; check	was	high byte 0	or 80h 		jnz		short main_loop		; it just was 80h in high byte,	go get 									; another dword retnull: 		pop		esi 		pop		edi retnull_bx: 		pop		ebx 		xor		eax,eax 		ret							; _cdecl return  chr_is_found: 		mov		eax,[edx - 4]		; let's look one more time on this dword 		cmp		al,bl				; is chr in	byte 0? 		je		short byte_0 		test	al,al				; test if low byte is 0 		je		retnull 		cmp		ah,bl				; is it	byte 1 		je		short byte_1 		test	ah,ah				; found	EOS	? 		je		retnull 		shr		eax,10h				; is it	byte 2 		cmp		al,bl 		je		short byte_2 		test	al,al				; if in	al some	bits were set, bl!=bh 		je		retnull 		cmp		ah,bl 		je		short byte_3 		test	ah,ah 		jz		retnull 		jmp		short main_loop		; neither chr nor EOS found, go	get 									; another dword byte_3: 		pop		esi 		pop		edi 		lea		eax,[edx - 1] 		pop		ebx					; restore ebx 		ret							; _cdecl return  byte_2: 		lea		eax,[edx - 2] 		pop		esi 		pop		edi 		pop		ebx 		ret							; _cdecl return  byte_1: 		lea		eax,[edx - 3] 		pop		esi 		pop		edi 		pop		ebx 		ret							; _cdecl return  byte_0: 		lea		eax,[edx - 4] 		pop		esi					; restore esi 		pop		edi					; restore edi 		pop		ebx					; restore ebx 		ret							; _cdecl return  strchr	endp 		end

user: user-3
content: 引用 3 楼 tudou12345679 的回复:您好，问您一个问题，这里有两个return,第一个如果执行了，第二个还会返回吗？ [quote=引用 2 楼 zhao4zhong1 的回复:] C:\Program Files\Microsoft Visual Studio\VC98\CRT\SRC\STRCHR.C /*** *strchr.c - search a string for a given character * *       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved. * *Purpose: *       defines strchr() - search a string for a character * *******************************************************************************/  #include <cruntime.h> #include <string.h>  /*** *char *strchr(string, c) - search a string for a character * *Purpose: *       Searches a string for a given character, which may be the *       null character '\0'. * *Entry: *       char *string - string to search in *       char c - character to search for * *Exit: *       returns pointer to the first occurence of c in string *       returns NULL if c does not occur in string * *Exceptions: * *******************************************************************************/  char * __cdecl strchr (         const char * string,         int ch         ) {         while (*string && *string != (char)ch)                 string++;          if (*string == (char)ch)                 return((char *)string);         return(NULL); } [/quote]  当然不会