PICC中函数传递结构体指针

只看该作者 · 2014-6-25 23:02

请教各位一个问题。大家有没有使用过函数参数使用结构体指针，PICC是否支持这种方式。我用了一次，编译能通过，但是仿真的时候，发现指针指向的是程序存储空间的地址，而非RAM区数据。高手给指点一下。谢谢！

2万 · 2014-6-26 08:40

可以使用。

你要正确的定义和使用指针，否则出现错误指向很正常。

只看该作者 · 2014-6-26 10:30

我使用的是PICC自带的time函数，使用time_t mktime（struct tm *ptr）函数来转换时间。仿真时发现指向事先定义的struct tm CurTime的结构体指针传进去之后，而在local窗口中发现显示的值不正确，不是CurTime的值。

测试程序如下，请各位帮忙分析。其中time.h和mktime.c：为PICC自带库函数。
//main.c

#include "pic18f67k22.h"
#include "time.h"

struct tm CurTime;
main()
{
time_t tt;

while(1)
{
CurTime.tm_sec = 20;
CurTime.tm_min = 0;
CurTime.tm_hour = 0;
CurTime.tm_mday = 1;
CurTime.tm_mon = 1;
CurTime.tm_year = 70;

tt = mktime(&CurTime);
}
}

//time.h

#ifndef _TIME

#ifndef _STDDEF
typedef int ptrdiff_t; /* result type of pointer difference */
typedef unsigned size_t; /* type yielded by sizeof */
typedef unsigned short wchar_t; /* wide char type */
#define _STDDEF
#define offsetof(ty, mem) ((int)&(((ty *)0)->mem))
#endif /* _STDDEF */

typedef long time_t; /* for representing times in seconds */
struct tm {
int tm_sec;
int tm_min;
int tm_hour;
int tm_mday;
int tm_mon;
int tm_year;
int tm_wday;
int tm_yday;
int tm_isdst;
};

#define CLOCKS_PER_SEC 1
#define clock() (-1L)
#define difftime(t1, t0) ((double)((time_t)(t1)-(time_t)(t0)))
#define _TIME
#endif /* _TIME */

extern int time_zone; /* minutes WESTWARD of Greenwich */
/* this value defaults to 0 since with
   operating systems like MS-DOS there is
   no time zone information available */

extern time_t time(time_t *); /* seconds since 00:00:00 Jan 1 1970 */
extern int stime(time_t *); /* set time */
extern char * asctime(const struct tm *); /* converts struct tm to ascii time */
extern char * ctime(const time_t *); /* current local time in ascii form */
extern struct tm * gmtime(const time_t *); /* Universal time */
extern struct tm * localtime(const time_t *); /* local time */
extern time_t mktime(struct tm *);
extern size_t strftime(char *, size_t, const char *, const struct tm *);

//mktime.c
#include <time.h>
#include <stdlib.h>
#include <string.h>

static int
isleap(unsigned yr)
{
return yr % 400 == 0 || (yr % 4 == 0 && yr % 100 != 0);
}

static unsigned
months_to_days(unsigned month)
{
return (month * 3057 - 3007) / 100;
}

static long
years_to_days (unsigned yr)
{
return yr * 365L + yr / 4 - yr / 100 + yr / 400;
}

/*
* Return the number of days. The function takes
* into account leap years.
*
* yr : must be greater than 0
* mo : must be between 1 and 12
* day: must be between 1 and 32
* */
static long
ymd_to_scalar(unsigned yr, unsigned mo, unsigned day)
{
long scalar;
scalar = day + months_to_days(mo);
if ( mo > 2 )                      /* adjust if past February */
   scalar -= isleap(yr) ? 1 : 2;
yr--;
scalar += years_to_days(yr);
return scalar;
}

time_t
mktime(struct tm *timeptr)
{
time_t tt;

if ((timeptr->tm_year < 70) || (timeptr->tm_year > 138))
{
      tt = (time_t)-1;
}
else
{
      tt = ymd_to_scalar(timeptr->tm_year + 1900,
                        timeptr->tm_mon + 1,
                        timeptr->tm_mday)
         - ymd_to_scalar(1970, 1, 1);
      tt = tt * 24 + timeptr->tm_hour;
      tt = tt * 60 + timeptr->tm_min;
      tt = tt * 60 + timeptr->tm_sec;
}
return tt;
}

只看该作者 · 2014-6-30 22:55

这个会不会是编译器优化的结果，结构体只有赋值语句，而且都是常量，处理日期时间的函数调用里也没有修改结构体里的变量值，编译器把它作为常量存储在程序存储区，做个单步调试然后查看一下对应的数据是否正确就能判断调用方式是否有问题了

PICC中函数传递结构体指针

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