出于某种原因，我在编译 .c 程序后收到一条错误消息。
生成 11 个警告。架构 x86_64 的未定义符号：“_main”，引用自：主要可执行文件 ld 的隐式入口/开始：未找到架构 x86_64 的符号：错误：链接器命令失败，退出代码为 1（使用 -v 查看调用）
我的日期.c：
#include "date.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
struct date {
char *day;
char *month;
char *year;
};
/*
* date_create creates a Date structure from `datestr`
* `datestr' is expected to be of the form "dd/mm/yyyy"
* returns pointer to Date structure if successful,
* NULL if not (syntax error)
*/
Date *date_create(char *datestr) {
Date *d = (Date *)malloc(sizeof(Date));
const char delimiter[2] = "/";
char *token;
if (d != NULL) {
token = strtok(datestr, delimiter);
d->day = *token;
token = strtok(NULL, delimiter);
d->month = *token;
token = strtok(NULL, delimiter);
d->year = *token;
}
};
/*
* date_duplicate creates a duplicate of `d'
* returns pointer to new Date structure if successful,
* NULL if not (memory allocation failure)
*/
Date *date_duplicate(Date *d) {
return NULL;
};
/*
* date_compare compares two dates, returning <0, 0, >0 if
* date1<date2, date1==date2, date1>date2, respectively
*/
int date_compare(Date *date1, Date *date2) {
return 0;
};
/*
* date_destroy returns any storage associated with `d' to the system
*/
void date_destroy(Date *d) {
};
重击输出：
bash-3.2$ gcc -W -Wall date.c
date.c:25:12: warning: incompatible integer to pointer conversion assigning to
'char *' from 'char'; remove * [-Wint-conversion]
d->day = *token;
^ ~~~~~~
date.c:27:14: warning: incompatible integer to pointer conversion assigning to
'char *' from 'char'; remove * [-Wint-conversion]
d->month = *token;
^ ~~~~~~
date.c:29:13: warning: incompatible integer to pointer conversion assigning to
'char *' from 'char'; remove * [-Wint-conversion]
d->year = *token;
^ ~~~~~~
date.c:37:44: warning: format specifies type 'void *' but the argument has type
'char' [-Wformat]
printf("Day: %p Month: %p Year: %p\n", *d->day, *d->month, *d->year);
~~ ^~~~~~~
%c
date.c:37:53: warning: format specifies type 'void *' but the argument has type
'char' [-Wformat]
printf("Day: %p Month: %p Year: %p\n", *d->day, *d->month, *d->year);
~~ ^~~~~~~~~
%c
date.c:37:64: warning: format specifies type 'void *' but the argument has type
'char' [-Wformat]
printf("Day: %p Month: %p Year: %p\n", *d->day, *d->month, *d->year);
~~ ^~~~~~~~
%c
date.c:40:1: warning: control reaches end of non-void function [-Wreturn-type]
};
^
date.c:47:28: warning: unused parameter 'd' [-Wunused-parameter]
Date *date_duplicate(Date *d) {
^
date.c:55:24: warning: unused parameter 'date1' [-Wunused-parameter]
int date_compare(Date *date1, Date *date2) {
^
date.c:55:37: warning: unused parameter 'date2' [-Wunused-parameter]
int date_compare(Date *date1, Date *date2) {
^
date.c:62:25: warning: unused parameter 'd' [-Wunused-parameter]
void date_destroy(Date *d) {
^
11 warnings generated.
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)