Remove fgets() compatbility function and related tests.

This patch removes the `tor_fgets()` wrapper around `fgets(3)` since it
is no longer needed. The function was created due to inconsistency
between the returned values of `fgets(3)` on different versions of Unix
when using `fgets(3)` on non-blocking file descriptors, but with the
recent changes in bug #21654 we switch from unbuffered to direct I/O on
non-blocking file descriptors in our utility module.

We continue to use `fgets(3)` directly in the geoip and dirserv module
since this usage is considered safe.

This patch also removes the test-case that was created to detect
differences in the implementation of `fgets(3)` as well as the changes
file since these changes was not included in any releases yet.

See: https://bugs.torproject.org/21654

changes/bug20988

@@ -1,4 +0,0 @@
-  o Minor bugfixes (portability):
-    - Add Tor compatibility function for fgets(3) due to inconsistency of
-      returned values in different supported C libraries. This fixes unit test
-      failures reported on FreeBSD. Fixes bug 20988.

src/common/compat.c

@@ -3476,45 +3476,6 @@ tor_getpass(const char *prompt, char *output, size_t buflen)
 #endif
 }
 
-/** Read at most one less than the number of characters specified by
- * <b>size</b> from the given <b>stream</b> and store it in <b>str</b>.
- *
- * Reading stops when a newline character is found or at EOF or error. If any
- * characters are read and there's no error, a trailing NUL byte is appended to
- * the end of <b>str</b>.
- *
- * Upon successful completion, this function returns a pointer to the string
- * <b>str</b>. If EOF occurs before any characters are read the function will
- * return NULL and the content of <b>str</b> is unchanged. Upon error, the
- * function returns NULL and the caller must check for error using foef(3) and
- * ferror(3).
- */
-char *
-tor_fgets(char *str, int size, FILE *stream)
-{
-  char *ret;
-
-  /* Reset errno before our call to fgets(3) to avoid a situation where the
-   * caller is calling us again because we just returned NULL and errno ==
-   * EAGAIN, but when they call us again we will always return NULL because the
-   * error flag on the file handler remains set and errno is set to EAGAIN.
-   */
-  errno = 0;
-
-  ret = fgets(str, size, stream);
-
-  /* FreeBSD, OpenBSD, Linux (glibc), and Linux (musl) seem to disagree about
-   * what to do in the given situation. We check if the stream has been flagged
-   * with an error-bit and return NULL in that situation if errno is also set
-   * to EAGAIN.
-   */
-  if (ferror(stream) && errno == EAGAIN) {
-    return NULL;
-  }
-
-  return ret;
-}
-
 /** Return the amount of free disk space we have permission to use, in
  * bytes. Return -1 if the amount of free space can't be determined. */
 int64_t

src/common/compat.h

@@ -740,8 +740,6 @@ STATIC int tor_ersatz_socketpair(int family, int type, int protocol,
 
 ssize_t tor_getpass(const char *prompt, char *output, size_t buflen);
 
-char *tor_fgets(char *str, int size, FILE *stream);
-
 /* This needs some of the declarations above so we include it here. */
 #include "compat_threads.h"
 

src/or/dirserv.c

@@ -2701,7 +2701,7 @@ dirserv_read_measured_bandwidths(const char *from_file,
     return -1;
   }
 
-  if (!tor_fgets(line, sizeof(line), fp)
+  if (!fgets(line, sizeof(line), fp)
           || !strlen(line) || line[strlen(line)-1] != '\n') {
     log_warn(LD_DIRSERV, "Long or truncated time in bandwidth file: %s",
              escaped(line));
@@ -2731,7 +2731,7 @@ dirserv_read_measured_bandwidths(const char *from_file,
 
   while (!feof(fp)) {
     measured_bw_line_t parsed_line;
-    if (tor_fgets(line, sizeof(line), fp) && strlen(line)) {
+    if (fgets(line, sizeof(line), fp) && strlen(line)) {
       if (measured_bw_line_parse(&parsed_line, line) != -1) {
         /* Also cache the line for dirserv_get_bandwidth_for_router() */
         dirserv_cache_measured_bw(&parsed_line, file_time);

src/or/geoip.c

@@ -346,7 +346,7 @@ geoip_load_file(sa_family_t family, const char *filename)
              (family == AF_INET) ? "IPv4" : "IPv6", filename);
   while (!feof(f)) {
     char buf[512];
-    if (tor_fgets(buf, (int)sizeof(buf), f) == NULL)
+    if (fgets(buf, (int)sizeof(buf), f) == NULL)
       break;
     crypto_digest_add_bytes(geoip_digest_env, buf, strlen(buf));
     /* FFFF track full country name. */

src/test/test_util.c

@@ -3940,116 +3940,6 @@ test_util_exit_status(void *ptr)
 #endif
 
 #ifndef _WIN32
-/* 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)
-{
-  int test_pipe[2] = {-1, -1};
-  int retval;
-  ssize_t retlen;
-  char *retptr;
-  FILE *test_stream = NULL;
-  char buf[4] = { 0 };
-
-  (void)ptr;
-
-  errno = 0;
-
-  /* Set up a pipe to test on */
-  retval = pipe(test_pipe);
-  tt_int_op(retval, OP_EQ, 0);
-
-  /* Set up the read-end to be non-blocking */
-  retval = fcntl(test_pipe[0], F_SETFL, O_NONBLOCK);
-  tt_int_op(retval, OP_EQ, 0);
-
-  /* Open it as a stdio stream */
-  test_stream = fdopen(test_pipe[0], "r");
-  tt_ptr_op(test_stream, OP_NE, NULL);
-
-  /* Send in a partial line */
-  retlen = write(test_pipe[1], "A", 1);
-  tt_int_op(retlen, OP_EQ, 1);
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, EAGAIN);
-  tt_ptr_op(retptr, OP_EQ, NULL);
-  tt_str_op(buf, OP_EQ, "A");
-  errno = 0;
-
-  /* Send in the rest */
-  retlen = write(test_pipe[1], "B\n", 2);
-  tt_int_op(retlen, OP_EQ, 2);
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, 0);
-  tt_ptr_op(retptr, OP_EQ, buf);
-  tt_str_op(buf, OP_EQ, "B\n");
-  errno = 0;
-  memset(buf, '\0', sizeof(buf));
-
-  /* Send in a full line */
-  retlen = write(test_pipe[1], "CD\n", 3);
-  tt_int_op(retlen, OP_EQ, 3);
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, 0);
-  tt_ptr_op(retptr, OP_EQ, buf);
-  tt_str_op(buf, OP_EQ, "CD\n");
-  errno = 0;
-  memset(buf, '\0', sizeof(buf));
-
-  /* Send in a partial line */
-  retlen = write(test_pipe[1], "E", 1);
-  tt_int_op(retlen, OP_EQ, 1);
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, EAGAIN);
-  tt_ptr_op(retptr, OP_EQ, NULL);
-  tt_str_op(buf, OP_EQ, "E");
-  errno = 0;
-
-  /* Send in the rest */
-  retlen = write(test_pipe[1], "F\n", 2);
-  tt_int_op(retlen, OP_EQ, 2);
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, 0);
-  tt_ptr_op(retptr, OP_EQ, buf);
-  tt_str_op(buf, OP_EQ, "F\n");
-  errno = 0;
-  memset(buf, '\0', sizeof(buf));
-
-  /* Send in a full line and close */
-  retlen = write(test_pipe[1], "GH", 2);
-  tt_int_op(retlen, OP_EQ, 2);
-  retval = close(test_pipe[1]);
-  tt_int_op(retval, OP_EQ, 0);
-  test_pipe[1] = -1;
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, 0);
-  tt_ptr_op(retptr, OP_EQ, buf);
-  tt_str_op(buf, OP_EQ, "GH");
-  errno = 0;
-
-  /* Check for EOF */
-  retptr = tor_fgets(buf, sizeof(buf), test_stream);
-  tt_int_op(errno, OP_EQ, 0);
-  tt_ptr_op(retptr, OP_EQ, NULL);
-  retval = feof(test_stream);
-  tt_int_op(retval, OP_NE, 0);
-  errno = 0;
-
-  /* Check that buf is unchanged according to C99 and C11 */
-  tt_str_op(buf, OP_EQ, "GH");
-  memset(buf, '\0', sizeof(buf));
-
- done:
-  if (test_stream != NULL)
-    fclose(test_stream);
-  if (test_pipe[0] != -1)
-    close(test_pipe[0]);
-  if (test_pipe[1] != -1)
-    close(test_pipe[1]);
-}
-
 static void
 test_util_string_from_pipe(void *ptr)
 {
@@ -5839,7 +5729,6 @@ struct testcase_t util_tests[] = {
   UTIL_TEST(num_cpus, 0),
   UTIL_TEST_WIN_ONLY(load_win_lib, 0),
   UTIL_TEST_NO_WIN(exit_status, 0),
-  UTIL_TEST_NO_WIN(fgets_eagain, 0),
   UTIL_TEST_NO_WIN(string_from_pipe, 0),
   UTIL_TEST(format_hex_number, 0),
   UTIL_TEST(format_dec_number, 0),