I confirmed that fread can read data from fp in EOF state on Linux. On OS X, freading from fp in EOF state doesn't work,
just return 0.

I tested this behavior using the following code.
----------------------------

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

main(void)
{
  FILE *fp1, *fp2;
  int n;
  char buf[128];

  fp1 = fopen("spam.txt", "w+");
  fputs("foo", fp1);

  fseek(fp1, 0L, SEEK_END);
  if (fread(buf, 1, sizeof(buf), fp1) == 0)
    fprintf(stderr, "first fread failed\n");

  fp2 = fopen("spam.txt", "a+");
  fputs("bar", fp2);
  fclose(fp2);

  if (feof(fp1))
    fprintf(stderr, "after appending some text, fp1 is still eof\n");

  if (fread(buf, 1, sizeof(buf), fp1) == 0)
    fprintf(stderr, "second fread failed\n");
  printf("buf: %s\n", buf);

  fclose(fp1);

  return 0;
}
----------------------------
=============
On Linux
=============
first fread failed
after appending some text, fp1 is still eof
buf: bar

=============
On OS X
=============
first fread failed
after appending some text, fp1 is still eof
second fread failed
buf: 

Anyway, I think it's safe and preferable to clear EOF indicator in this case.