What is the bug in the following program?   #include <stdlib.h>  #include <stdio.h>  #define SIZE 15   int main()  {      int *a, i;      a = malloc(SIZE*sizeof(int));      for (i=0; i<SIZE; i++)          *(a + i) = i * i;      for (i=0; i<SIZE; i++)          printf("%d\n", *a++);      free(a);      return 0;  }

Is the following a valid C program? If so, what is the output of it?   #include <stdio.h>  int main()  {    int a=3, b = 5;    printf(&a["Ya!Hello! how is this? %s\n"], &b["junk/super"]);    printf(&a["WHAT%c%c%c  %c%c  %c !\n"], 1["this"],       2["beauty"],0["tool"],0["is"],3["sensitive"],4["CCCCCC"]);    return 0;  }

#include <stdio.h>int main(){int a[] = {0, 1, 2};printf(“%d, %d, %d\n”, 0[a], 1[a], 2[a]);return 0;}

What is the output of the following, if the input provided is:Life is beautiful   #include <stdio.h>  int main()  {      char dummy[80];      printf("Enter a string:\n");      scanf("%[^a]",dummy);      printf("%s\n",dummy);      return 0;  }

第四十一题

Note : This question has more to do with Linker than C language We have three files a.c, b.c and main.c respectively as follows: a.c--- int a;b.c--- int a = 10;main.c------ extern int a;int main(){        printf("a = %d\n",a);        return 0;}Let‘s see what happens, when the files are compiled together: bash$ gcc a.c b.c main.cbash$ ./a.outa = 10Hmm!! no compilation/linker error!!! Why is it so??

知识点讲解：

参考《C陷阱与缺陷》第67页 4.2 申明与定义。

若一个文件中定义int a，另一个文件中定义int a，编译不会有问题，编译器将a初始化为0；

若一个文件中定义int a，另一个文件中定义int a=10，a的值为10；

若一个文件中定义int a=1，另一个文件中定义int a=10，编译会有重复定义的错误。

第四十二题

The following is the offset macros which is used many a times. Figure out what is it trying to do and what is the advantage of using it.   #define offsetof(a,b) ((int)(&(((a*)(0))->b)))

知识点讲解：

计算结构体成员变量在结构体中的偏移。a为结构体类型，b为成员变量。

第四十三题

The following is the macro implementation of the famous, Triple xor swap.   #define SWAP(a,b) ((a) ^= (b) ^= (a) ^= (b))What are the potential problems with the above macro?

知识点讲解：

参考博文：http://www.cnblogs.com/tanghuimin0713/p/3220665.html的评论。

此方法有如下局限：

1）a和b不能是同一个变量，即如果执行SWAP(a, a)那么不管原来a值是多少，执行后a值被置为0； 

2）a和b不能是浮点数，异或操作对浮点数没有意义； 

3）a和b不能是结体体等复合数据类型，原因同上； 

4）a或b不能是表达式；

第四十四题

What is the use of the following macro?   #define DPRINTF(x) printf("%s:%d\n",#x,x)

题目讲解：

打印x的值。

如a=10，DPRINTF(a)的结果为“a:10“。

第四十五题

Let‘s say you were asked to code a function IAddOverFlow which takes three parameters, pointer to an integer where the result is to be stored, and the two integers which needs to be added. It returns 0 if there is an overflow and 1 otherwise:   int IAddOverFlow(int* result,int a,int b)  {      /* ... */  }So, how do you code the above function? (To put in a nutshell, what is the logic you use for overflow detection?)

题目讲解：

检测溢出的方法参考：http://www.fefe.de/intof.html