程序比程序员更理解c语言！ cdecl程序（分析c语言的声明

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c语言的声明有时侯是很复杂的；比如int (*a[5])(int); 再比如:int*((*p)(int))(int);你能说明白它们的意思吗？

像这样的声明很容易把一般的程序员弄蒙逼的。

cdecl是一个分析这种声明的程序，输入声明形式，用英语输出其描述。

一个在线的cdecl.

我们也可以自己编写分析程序。编写一个这样的分析程序，很有助于帮助我们理解c语言的声明。

下面是照着《c专家编程》敲的cdecl程序。

/* * ===================================================================================== * *       Filename:  cdecl.c * *    Description:   * *        Version:  1.0 *        Created:  2012年02月28日 21时54分11秒 *       Revision:  none *       Compiler:  gcc * *         Author:  MaZheng (blog.csdn.net/mazheng1989), mazheng19891019@gmail.com *        Company:  Dalian University Of Technology * * ===================================================================================== */#include<stdio.h>#include<string.h>#include<ctype.h>#include<stdlib.h>#define MAXTOKENS 100/*  */#defineMAXTOKENLEN 64/*  */enum type_tag{ IDENTIFIER,QUALIFIER,TYPE};struct token{char type;char string[MAXTOKENLEN];};int top =-1;struct token stack[MAXTOKENS];struct token this;#definepop stack[top--]/*  */#definepush(s) stack[++top]=s/*  */enum type_tag classify_string(void )/*推断标识符的类型*/{char *s=this.string;if(!strcmp(s,"const")){strcpy(s,"read-only");return QUALIFIER;}if(!strcmp(s,"volatile")) return QUALIFIER;if(!strcmp(s,"void")) return TYPE;if(!strcmp(s,"char")) return TYPE;if(!strcmp(s,"signed")) return TYPE;if(!strcmp(s,"unsigned")) return TYPE;if(!strcmp(s,"short")) return TYPE;if(!strcmp(s,"int")) return TYPE;if(!strcmp(s,"long")) return TYPE;if(!strcmp(s,"float")) return TYPE;if(!strcmp(s,"double")) return TYPE;if(!strcmp(s,"struct")) return TYPE;if(!strcmp(s,"union")) return TYPE;if(!strcmp(s,"enum")) return TYPE;return IDENTIFIER;}void gettoken(void)/*读取下一个标记到 this*/{char *p=this.string;/*略过空白字符*/while((*p=getchar())==' ');if(isalnum(*p)){/*读入的标识符以A—Z，0-9开头*/while(isalnum(*++p=getchar()));ungetc(*p,stdin);*p='\0';this.type=classify_string();return;}if(*p=='*'){strcpy(this.string,"pointer to");this.type='*';return ;}this.string[1]='\0';this.type=*p;return ;}void read_to_first_identifier(){gettoken();while(this.type!=IDENTIFIER){push(this);gettoken();}printf("%s is ",this.string);gettoken();}void deal_with_arrays(){while(this.type=='['){printf("array ");gettoken();/*数字或']'*/if(isdigit(this.string[0])){int temp;sscanf(this.string,"%d",&temp);printf("0..%d ",temp-1);gettoken();/*读取']'*/}gettoken();/*读取']'之后的再一个标记*/printf("of ");}}void deal_with_function_args(){/*处理函数参数*/while(this.type!=')'){gettoken();}gettoken();printf("function returning ");}void deal_with_pointers(){while(stack[top].type=='*'){printf("%s ",pop.string);}}void deal_with_declarator(){/*处理标识符之后可能存在的数组/函数*/switch(this.type){case '[':deal_with_arrays(); break;case '(': deal_with_function_args(); break;}deal_with_pointers();/*处理在读入到标识符之前压入到堆栈的符号*/while(top>=0){if(stack[top].type=='('){pop;gettoken();/*读取')'之后的符号*/deal_with_declarator();}else{printf("%s ",pop.string);}}}int main(){/*将标记呀入堆栈中，直到遇见标识符*/read_to_first_identifier();deal_with_declarator();printf("\n");return 0;}

编译：gcc cdecl.c -o cdecl

输入： int *((*p)(int))(int)
输出：p is pointer to function returning function returning pointer to int