Fix insert-file-contents infloop with unlucky END

This partially reverts 55f41ca3aa8fe487d10730708a7396137a2c9d18,
which was a partial fix for Bug#77315.
* src/fileio.c (Finsert_file_contents): Go back to accepting
partial reads when doing the optimized way when code conversion is
not needed.  This avoids an unlikely bug when END happens to lie
at a buffer boundary, causing an infloop.  For consistency, do the
same when doing code conversion (though there’s no bug in then),
as there’s not a real need for emacs_full_read there either.

(cherry picked from commit 27e0f0f79b9c97796fc89fedf3c05517532f0475)

diff --git a/src/fileio.c b/src/fileio.c
index 9b47b565458fe8a721b9dff0e3438c917aedee58..76e5e56190e8105e82714fdcf5a52ae5d89cb9cc 100644 (file)
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -4454,42 +4454,10 @@ by calling `format-decode', which see.  */)
          bytes_to_read = min (bytes_to_read, end_offset - curpos);
          ptrdiff_t nread = (bytes_to_read <= 0
                             ? 0
-                            : emacs_full_read (fd, read_buf, bytes_to_read));
+                            : emacs_fd_read (fd, read_buf, bytes_to_read));
          if (nread < 0)
            report_file_error ("Read error", orig_filename);
-
-         if (0 < nread)
-           {
-             curpos += nread;
-
-             if (CODING_REQUIRE_DETECTION (&coding))
-               {
-                 coding_system
-                   = detect_coding_system ((unsigned char *) read_buf,
-                                           nread, nread, 1, 0,
-                                           coding_system);
-                 setup_coding_system (coding_system, &coding);
-               }
-
-             if (CODING_REQUIRE_DECODING (&coding))
-               /* We found that the file should be decoded somehow.
-                  Let's give up here.  */
-               {
-                 giveup_match_end = true;
-                 break;
-               }
-
-             ptrdiff_t bufpos = 0;
-             ptrdiff_t bufposlim = min (nread, same_at_end - same_at_start);
-             while (bufpos < bufposlim
-                    && FETCH_BYTE (same_at_start) == read_buf[bufpos])
-               same_at_start++, bufpos++;
-             /* If we found a discrepancy, stop the scan.  */
-             if (bufpos != nread)
-               break;
-           }
-
-         if (nread < bytes_to_read)
+         else if (nread == 0)
            {
              /* Data inserted from the file match the buffer's leading bytes,
                 so there's no need to replace anything.  */
@@ -4500,6 +4468,33 @@ by calling `format-decode', which see.  */)
              del_range_byte (same_at_start, same_at_end);
              goto handled;
            }
+
+         curpos += nread;
+
+         if (CODING_REQUIRE_DETECTION (&coding))
+           {
+             coding_system = detect_coding_system ((unsigned char *) read_buf,
+                                                   nread, nread, 1, 0,
+                                                   coding_system);
+             setup_coding_system (coding_system, &coding);
+           }
+
+         if (CODING_REQUIRE_DECODING (&coding))
+           /* We found that the file should be decoded somehow.
+               Let's give up here.  */
+           {
+             giveup_match_end = true;
+             break;
+           }
+
+         ptrdiff_t bufpos = 0;
+         ptrdiff_t bufposlim = min (nread, same_at_end - same_at_start);
+         while (bufpos < bufposlim
+                && FETCH_BYTE (same_at_start) == read_buf[bufpos])
+           same_at_start++, bufpos++;
+         /* If we found a discrepancy, stop the scan.  */
+         if (bufpos != nread)
+           break;
        }
       off_t same_at_start_pos = beg_offset + (same_at_start - BEGV_BYTE);
 
@@ -4692,7 +4687,7 @@ by calling `format-decode', which see.  */)
             quitting while reading a huge file.  */
 
          ptrdiff_t trial = sizeof read_buf - unprocessed;
-         this = emacs_full_read (fd, read_buf + unprocessed, trial);
+         this = emacs_fd_read (fd, read_buf + unprocessed, trial);
          if (this < 0)
            report_file_error ("Read error", orig_filename);
          if (this == 0)
@@ -4706,8 +4701,6 @@ by calling `format-decode', which see.  */)
          unprocessed = coding.carryover_bytes;
          if (coding.carryover_bytes > 0)
            memcpy (read_buf, coding.carryover, unprocessed);
-         if (this < trial)
-           break;
        }
 
       emacs_fd_close (fd);