Fixed fgets_eagain unit test.

On a non-blocking pipe fgets sets EAGAIN when it encounters partial lines. No
error is set on full lines or EOF. EOF is reached when the writing end of the
pipe is closed. Partial lines and full lines are both returned by fgets, EOF
results in NULL.

Mention of this behaviour can be found in #1903 and #2045.

src/test/test_util.c

@@ -2447,8 +2447,9 @@ test_util_exit_status(void *ptr)
 #endif
 
 #ifndef _WIN32
-/** Check that fgets waits until a full line, and not return a partial line, on
- * a EAGAIN with a non-blocking pipe */
+/* Check that fgets with a non-blocking pipe returns partial lines and sets
+ * EAGAIN, returns full lines and sets no error, and returns NULL on EOF and
+ * sets no error */
 static void
 test_util_fgets_eagain(void *ptr)
 {
@@ -2457,17 +2458,19 @@ test_util_fgets_eagain(void *ptr)
   ssize_t retlen;
   char *retptr;
   FILE *test_stream = NULL;
-  char buf[10];
+  char buf[4] = { 0 };
 
   (void)ptr;
 
+  errno = 0;
+
   /* Set up a pipe to test on */
   retval = pipe(test_pipe);
-  tt_int_op(retval, >=, 0);
+  tt_int_op(retval, ==, 0);
 
   /* Set up the read-end to be non-blocking */
   retval = fcntl(test_pipe[0], F_SETFL, O_NONBLOCK);
-  tt_int_op(retval, >=, 0);
+  tt_int_op(retval, ==, 0);
 
   /* Open it as a stdio stream */
   test_stream = fdopen(test_pipe[0], "r");
@@ -2477,51 +2480,69 @@ test_util_fgets_eagain(void *ptr)
   retlen = write(test_pipe[1], "A", 1);
   tt_int_op(retlen, ==, 1);
   retptr = fgets(buf, sizeof(buf), test_stream);
-  tt_want(retptr == NULL);
   tt_int_op(errno, ==, EAGAIN);
+  tt_ptr_op(retptr, ==, buf);
+  tt_str_op(buf, ==, "A");
+  errno = 0;
 
   /* Send in the rest */
   retlen = write(test_pipe[1], "B\n", 2);
   tt_int_op(retlen, ==, 2);
   retptr = fgets(buf, sizeof(buf), test_stream);
+  tt_int_op(errno, ==, 0);
   tt_ptr_op(retptr, ==, buf);
-  tt_str_op(buf, ==, "AB\n");
+  tt_str_op(buf, ==, "B\n");
+  errno = 0;
 
   /* Send in a full line */
   retlen = write(test_pipe[1], "CD\n", 3);
   tt_int_op(retlen, ==, 3);
   retptr = fgets(buf, sizeof(buf), test_stream);
+  tt_int_op(errno, ==, 0);
   tt_ptr_op(retptr, ==, buf);
   tt_str_op(buf, ==, "CD\n");
+  errno = 0;
 
   /* Send in a partial line */
   retlen = write(test_pipe[1], "E", 1);
   tt_int_op(retlen, ==, 1);
   retptr = fgets(buf, sizeof(buf), test_stream);
-  tt_ptr_op(retptr, ==, NULL);
   tt_int_op(errno, ==, EAGAIN);
+  tt_ptr_op(retptr, ==, buf);
+  tt_str_op(buf, ==, "E");
+  errno = 0;
 
   /* Send in the rest */
   retlen = write(test_pipe[1], "F\n", 2);
   tt_int_op(retlen, ==, 2);
   retptr = fgets(buf, sizeof(buf), test_stream);
+  tt_int_op(errno, ==, 0);
   tt_ptr_op(retptr, ==, buf);
-  tt_str_op(buf, ==, "EF\n");
+  tt_str_op(buf, ==, "F\n");
+  errno = 0;
 
   /* Send in a full line and close */
   retlen = write(test_pipe[1], "GH", 2);
   tt_int_op(retlen, ==, 2);
   retval = close(test_pipe[1]);
-  test_pipe[1] = -1;
   tt_int_op(retval, ==, 0);
+  test_pipe[1] = -1;
   retptr = fgets(buf, sizeof(buf), test_stream);
+  tt_int_op(errno, ==, 0);
   tt_ptr_op(retptr, ==, buf);
   tt_str_op(buf, ==, "GH");
+  errno = 0;
 
   /* Check for EOF */
   retptr = fgets(buf, sizeof(buf), test_stream);
+  tt_int_op(errno, ==, 0);
   tt_ptr_op(retptr, ==, NULL);
-  tt_int_op(feof(test_stream), >, 0);
+  retval = feof(test_stream);
+  tt_int_op(retval, !=, 0);
+  errno = 0;
+
+  /* Check that buf is unchanged according to C99 and C11 */
+  tt_str_op(buf, ==, "GH");
 
  done:
   if (test_stream != NULL)
@@ -3782,7 +3803,7 @@ struct testcase_t util_tests[] = {
 #endif
 #ifndef _WIN32
   UTIL_TEST(exit_status, 0),
-  UTIL_TEST(fgets_eagain, TT_SKIP),
+  UTIL_TEST(fgets_eagain, 0),
 #endif
   UTIL_TEST(spawn_background_ok, 0),
   UTIL_TEST(spawn_background_fail, 0),