$ cat leak.c

#include <fcntl.h>

void test ()
{
   int fd = open("test", O_RDONLY);
}

void main(){}

$ gcc-11.2.0 leak.c -fanalyzer

leak.c: In function ‘test’:
leak.c:6:1: warning: leak of FILE ‘fd’ [CWE-775] [-Wanalyzer-file-leak]
    6 | }
      | ^
  ‘test’: events 1-2
    |
    |    5 |    int fd = open("test", O_RDONLY);
    |      |             ^~~~~~~~~~~~~~~~~~~~~~
    |      |             |
    |      |             (1) opened here
    |    6 | }
    |      | ~            
    |      | |
    |      | (2) leaks here
    |

$ cat leak-by-not-saving.c

#include <fcntl.h>

void test ()
{
   open("test", O_RDONLY);
}

void main(){}

$ gcc leak-by-not-saving.c -fanalyzer

leak.c: In function ‘test’:
leak.c:5:4: warning: leak by not saving fd [CWE-775] [-Wanalyzer-file-leak]
    5 |    open("test", O_RDONLY);
      |    ^~~~~~~~~~~~~~~~~~~~~~
  ‘test’: event 1
    |
    |    5 |    open("test", O_RDONLY);
    |      |    ^~~~~~~~~~~~~~~~~~~~~~
    |      |    |
    |      |    (1) leak by not saving fd
    |