assert、atexit、bsearch、tolower、offsetof及va_list

1.屏蔽assert函数

#define NDEBUG  ("no debug")    //shield the function of assert ... #include <assert.h>#include <stdlib.h>voidopen_record(char *record_name){    assert(record_name!=NULL);        /* Rest of code */    printf("\nRecord name is:%s\n", record_name);}intmain(void){      open_record(NULL);      open_record("I love janesnf...");      open_record(NULL);      return 0;}

2. 调用atexit

#include <stdio.h>#include <stdlib.h>voidtest_atexit0(void){    printf("\nHosfore 000000 is using atexit function ...\n");}voidtest_atexit(void){    printf("\nHosfore is using atexit function ...\n");}intmain(){    int i = 0;    atexit(test_atexit);    atexit(test_atexit0);    atexit(test_atexit);    atexit(test_atexit0);    for (; i < 100; i++)        printf("\n----\n");    return 0;}

3.调用二分搜索函数，搜索从数组的平均值开始

#include <stdlib.h>#include <stdio.h>#include <assert.h>#define  DEBUG 0intcompare(const void *key, const void *current){    assert(key != NULL);    assert(current != NULL);#if(DEBUG)    printf("\nIn %s and key val:%d, current val:%d\n",\            __func__, *(int*)key, *(int*)current);#endif    if (*(int*)key > *(int*)current)        return 1;    else if (*(int*)key == *(int*)current)        return 0;    else        return -1;}intmain(){    int key = 2, arr[10], i = 0, *rt;    for (; i < 10; i++)       arr[i] = 2+i;#if(DEBUG)    printf("\nIn %s and sizeof arr is:%d, sizeof int is:%d\n",\             __func__, sizeof(arr)/sizeof(arr[0]), sizeof(int));#endif    rt = bsearch(&key, arr, sizeof(arr)/sizeof(arr[0]), sizeof(int), compare);    if (rt)        printf("\nbsearch result of key:%d  is:%d and memory addr is:%p\n",\                key, *rt, rt);    return 0;}

 4.大小写字母转换函数调用

#include<ctype.h>#include<stdio.h>#include<string.h>int main(void){    int loop;    char string[]="THIS IS A TEST";    printf("Orig: %s\n",string);    for(loop=0;loop<strlen(string);loop++)        string[loop]=tolower(string[loop]);    printf("Tolowered:  %s\n",string);    return 0;}

 

5.求结构体属性在其内部地址偏移函数offsetof

 

#include<stddef.h>#include<stdio.h>int main(void){    struct user{        char name[50];        char alias[50];        int level;    };    printf("level is the %d byte in the user structure.\n",             offsetof(struct user,level));}

 

6.支持不定参数个数的函数（源自网络）

#include<stdarg.h>#include<stdio.h>voidsum(char *, int, ...);intmain(void){    sum("The sum of 10+15+13 is %d.\n",3,10,15,13);    return 0;}voidsum(char *string, int num_args, ...){    int sum=0;    va_list ap;    int loop;    va_start(ap,num_args);    for(loop=0;loop<num_args;loop++)        sum+=va_arg(ap,int);    printf(string,sum);    va_end(ap);}