以下c程序中的错误是什么？

Question

a.c:
#include "a.h"
double GetTimeStamp()
{
            struct timespec start;

            if((clock_gettime( CLOCK_REALTIME, &start)) == -1 )
            {
              perror("clock gettime\n");

            }

/* I am calculating the Clock granularity here the granularity is basically how long that timer interrupt
 * will last while it's processing the background task.*/
            //micro seconds output
        return (1e3 * start.tv_sec + start.tv_nsec * 1e-3);

}

int a()
{
intr_rx_time = GetTimeStamp();
IPLatency = intr_rx_time;

}

---

a.h:
a();
double intr_rx_time, IPLatency;

---

b.c:
#include "a.h"
extern double IPLatency;
uint32 ipLatency;

int main()
{
  ipLatency = (uint32)IPLatency;
  printf("Current IP Latency microseconds: %ld\n", ipLatency);
}

在上面：我正在计算来自 a.c 程序的时间戳。稍后我正在读取 b.c 程序中的计算时间戳值，如上所示。但是我在 b.c 程序中将输出设为 0。上述程序中的错误是什么？有人可以帮忙吗？

Answer 1

a.c 和 b.c 中的 intr_rx_time 和 IPLatency 是不同的对象。

将extern 添加到头文件（从“定义”更改为“声明”）并在单个.c 文件中定义变量（不带extern）。

// a.h
int a(void);
extern double intr_rx_time, IPLatency;

---

// a.c
#include <stdio.h>
#include <time.h>
#include "a.h"
double GetTimeStamp(void)
{
    struct timespec start;
    if ((clock_gettime(CLOCK_REALTIME, &start)) == -1) {
        perror("clock gettime");
    }
    /* I am calculating the Clock granularity here the granularity is basically how long that timer interrupt
     * will last while it's processing the background task. */
    //micro seconds output
    return (1e3 * start.tv_sec + start.tv_nsec * 1e-3);
}

int a(void)
{
    intr_rx_time = GetTimeStamp();
    IPLatency = intr_rx_time;
}

---

// b.c
#include <inttypes.h>
#include <stdio.h>
#include "a.h"
double IPLatency;
uint32 ipLatency;

int main(void)
{
    ipLatency = IPLatency;
    printf("Current IP Latency microseconds: %" PRIu32 "\n", ipLatency);
}

Answer 2

1) 将 double intr_rx_time, IPLatency; 从 a.h 移动到 a.c

2) a.h 中的原型

a();

应该是

int a(void);

3) 将以下行添加到 a.h

#include<time.h> 
#include<stdio.h>
typedef unsigned int uint32;

4) 在 b.c 中将 %ld 更改为 %d