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Date: Thu, 14 Sep 2006 05:13:54 -0600
From: Eric Blake <ebb9 AT byu DOT net>
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To: cygwin AT cygwin DOT com
Subject: Re: bash-3.1-7　BUG
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According to Christopher Faylor on 9/13/2006 8:07 PM:
> 
> I doubt that Eric will want to deal with the fallout of having bash not
> understand \r\n line endings but, if he does, it would be his decision
> and, again, I would support it 100%.  I am very eager to see things like
> configure scripts work faster and if we have to drop a few scared or
> lazy people along the way to accomplish that goal, that's fine with me.
> I have no problem at all with being a part of a smaller community which
> doesn't need to use notepad to edit their bash scripts.

Here's the difference between 3.1-7 and 3.1-8:

diff -u bash-3.1/input.c bash-3.1/input.c
- --- bash-3.1/input.c    2006-09-08 16:58:58.703125000 -0600
+++ bash-3.1/input.c    2006-09-14 04:13:11.359375000 -0600
@@ -166,6 +166,10 @@
   bp->b_used = bp->b_inputp = bp->b_flag = 0;
   if (bufsize == 1)
     bp->b_flag |= B_UNBUFF;
+#ifdef __CYGWIN__
+  if ((fcntl (fd, F_GETFL) & O_TEXT) != 0)
+    bp->b_flag |= B_TEXT;
+#endif
   return (bp);
 }

@@ -442,6 +446,25 @@
 {
   ssize_t nr;

+#ifdef __CYGWIN__
+  /* lseek'ing on text files is problematic; lseek reports the true
+     file offset, but read collapses \r\n and returns a character
+     count.  We cannot reliably seek backwards if nr is smaller than
+     the seek offset encountered during the read, and must instead
+     treat the stream as unbuffered.  */
+  if ((bp->b_flag & (B_TEXT | B_UNBUFF)) == B_TEXT)
+    {
+      off_t offset = lseek (bp->b_fd, 0, SEEK_CUR);
+      nr = zread (bp->b_fd, bp->b_buffer, bp->b_size);
+      if (nr > 0 && nr < lseek (bp->b_fd, 0, SEEK_CUR) - offset)
+       {
+         lseek (bp->b_fd, offset, SEEK_SET);
+         bp->b_flag |= B_UNBUFF;
+         nr = zread (bp->b_fd, bp->b_buffer, bp->b_size = 1);
+       }
+    }
+  else
+#endif
   nr = zread (bp->b_fd, bp->b_buffer, bp->b_size);
   if (nr <= 0)
     {
@@ -454,15 +477,6 @@
       return (EOF);
     }

- -#if defined (__CYGWIN__)
- -  /* If on cygwin, translate \r\n to \n. */
- -  if (nr >= 2 && bp->b_buffer[nr - 2] == '\r' && bp->b_buffer[nr - 1] ==
'\n')
- -    {
- -      bp->b_buffer[nr - 2] = '\n';
- -      nr--;
- -    }
- -#endif
- -
   bp->b_used = nr;
   bp->b_inputp = 0;
   return (bp->b_buffer[bp->b_inputp++] & 0xFF);
only in patch2:
unchanged:
- --- bash-3.1-orig/input.h       2002-01-30 07:11:47.000000000 -0700
+++ bash-3.1/input.h    2006-09-14 03:29:05.484375000 -0600
@@ -47,6 +47,7 @@
 #define B_ERROR                0x02
 #define B_UNBUFF       0x04
 #define B_WASBASHINPUT 0x08
+#define B_TEXT         0x10 /* Text stream, when O_BINARY is nonzero */

 /* A buffered stream.  Like a FILE *, but with our own buffering and
    synchronization.  Look in input.c for the implementation. */


My thoughts on the matter are that if you use binary mounts (and I highly
recommend them), then every character in your file is important.  Since
bash on Linux does not ignore \r, and POSIX does not allow bash to ignore
\r by default (although you can set IFS to include \r as a whitespace
character to ignore), then neither should bash on a binary cygwin file.
If you use text mounts, then this patch is smart enough to buffer data up
until the point that an \r\n pair is converted by the text mode file into
a single character, at which point the lseek optimization breaks down and
the text mode file is subsequently processed a byte at a time.  If you
need DOS line endings, use a text mount.  If you need speed, use UNIX line
endings on a binary mount, although even UNIX line endings on a text mount
will be faster than DOS line endings.  Case closed, since I'm the
maintainer, and I really don't want to bother with anything larger than
the above patch (and also plan on submitting the above patch upstream,
where it is less likely to be accepted if it is larger).

- --
Life is short - so eat dessert first!

Eric Blake             ebb9 AT byu DOT net
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