strstr() 是否返回一个指向 malloced 内存的指针，需要我稍后手动释放它？

Question

I have a parser method that is parsing an API call. I am using strstr() in my parsing function. My parse_api function is allowing me to return the pointer returned by strstr . Am I correct in assuming that this means strstr mallocs a memory space and I need to free it?

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

char *parse_api(char *str);

int main() {
    char str[] = "dadsadsdsdsdamountdsafoodsd";
    puts(parse_api(str));
    return 0;
}
  
char *parse_api(char *str) {
    char *needle;
    char *updated_needle;
    needle = strstr(str, "amount");
    puts(needle);
    updated_needle = needle + 9;
    updated_needle[strlen(updated_needle) - 3] = '\0';
    return updated_needle;
}

Answer 1

The strstr function does not return alloc'ed memory. It returns a pointer to the start of the substring inside of the haystack parameter.

So in this case strstr will return str + 12 .

Answer 2

In the documentation, strstr the following describes the returned value:

Pointer to the first character of the found substring in str , or a null pointer if such substring is not found. If substr points to an empty string, str is returned.

When it says it returns a pointer to the first character of the substring, it means that quite literally. It points to a location within str . In your case, it returns str + 12 . No memory is allocated.

Note: This means that the value returned by strstr stops being valid if str is changed or freed!