C專家編程之編譯器日期被破壞程序

C專家編程之編譯器日期被破壞程序

#include
#include
#include
#include

#define CHOICE 2
#define FILEPATH "/root/date.c"

char global_buffer[120];


//NO.1 使用全局聲明的數組
#if CHOICE == 1
char *local_time(char* filename)
{
        struct tm *tm_ptr;
        struct stat stat_block; 

        stat(filename , &stat_block);

        tm_ptr = localtime(&stat_block.st_mtime);

        strftime(global_buffer, sizeof(global_buffer), "%a %b %e %T %Y",tm_ptr);
	printf("using global array!\n");
        return global_buffer;
}


/* NO.2 顯式分配一些內存，保存返回的值*/
#elif CHOICE == 2
char *local_time(char* filename)
{
	struct tm *tm_ptr;
	struct stat stat_block;
	char *buffer = (char*)malloc(120);
	
	stat(filename , &stat_block);
	
	tm_ptr = localtime(&stat_block.st_mtime);
	
	strftime(buffer, 120, "%a %b %e %T %Y",tm_ptr);
	printf("using malloc memory!\n");
	
	return buffer;
}

//No.3 使用靜態數組
#else 
char *local_time(char* filename)
{
        struct tm *tm_ptr;
        struct stat stat_block;
        static char buffer[120];

        stat(filename , &stat_block);

        tm_ptr = localtime(&stat_block.st_mtime);

        strftime(buffer, sizeof(buffer), "%a %b %e %T %Y",tm_ptr);
	printf("using static array!\n");

        return buffer;
}
#endif



int main()
{
	char *s = FILEPATH;
#if CHOICE == 1
	//char *ptr = (char *) malloc(120);
	char *p = local_time(s);
	printf("%s\n",p);
#elif CHOICE == 2
	char *p = local_time(s);
	printf("%s\n",p);
	//free(p);
#else
	char *p = local_time(s);
	printf("%s\n",p);
#endif	
}