我怎么能写返回在C字符串的函数？

问题描述

当我尝试使用的printf（％S，course_comment（1.0））打电话给我的功能; ，程序崩溃。这是我的功能：

When I try calling my function using printf(" %s",course_comment(1.0) );, the program crashes. This is my function:

char *course_comment(float b)
{
   if(b < 2.0)
     return("Retake");
}

为什么它会崩溃？我怎样才能解决这个问题？

Why does it crash? How can I fix it?

推荐答案

如果你的字符串是常数，也无意修改结果，字符串的工作是最好的选择，例如：

If your strings are constants and there is no intention to modify the result, working with string literals is the best choice, e.g.:

#include <stdio.h>

static const char RETAKE_STR[] = "Retake";
static const char DONT_RETAKE_STR[] = "Don't retake";

const char *
course_comment (float b)
{
  return b < 2.0 ? RETAKE_STR : DONT_RETAKE_STR;
}

int main()
{
  printf ("%s or... %s?\n",
      course_comment (1.0),
      course_comment (3.0));
  return 0;
}

另外，你可以使用的strdup 克隆字符串（不要忘了免费吧）：

Otherwise, you can use strdup to clone the string (and don't forget to free it):

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char *
course_comment (float b)
{
  char result[256];

  if (b < 2.0)
    {
      snprintf (result, sizeof (result), "Retake %f", b);
    }
  else
    {
      snprintf (result, sizeof (result), "Do not retake %f", b);
    }
  return strdup (result);
}

int main()
{
  char *comment;

  comment = course_comment (1.0);
  printf ("Result: %s\n", comment);
  free (comment); // Don't forget to free the memory!

  comment = course_comment (3.0);
  printf ("Result: %s\n", comment);
  free (comment); // Don't forget to free the memory!

  return 0;
}

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