有时候，C语言声明十分反人类……于是，cdecl应运而生~~~

//
// main.cpp
// f-cdecl
//
// Created by ZYJ on 2016/11/2.
// Copyright © 2016年 ZYJ. All rights reserved.
//

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

#define MAXTOKENS 100
#define MAXTOKENLEN 64

#define pop stack[top--]
#define push(s) stack[++top] = s

enum type_tag
{
    IDENTIFIER, QUALIFIER, TYPE
};

struct token
{
    char type;
    char string[MAXTOKENLEN];
};

int top = -1;
struct token stack[MAXTOKENS];
struct token this_;

enum type_tag classify_string()     // 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() // 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;
}

PS：源码来自《C专家编程》，Xcode [Version 8.1 (8B62)]亲测无误。