At some point between Diffutils 2.8.7 and 2.9, the code that handles
binary files was removed from io.c.  The changes below resurrect the
correct behavior.  To accomplish this, I needed to add the binary-io
module, and make changes there as well.  Patches are below.

Thanks.

2012-05-12  Eli Zaretskii  <e...@gnu.org>

        * lib/binary-io.h (SET_BINARY) [O_BINARY]: Return the previous mode.
        (UNSET_BINARY): New macro, to reset I/O to text mode.
        (SET_BINARY, UNSET_BINARY): Include _WIN32 in the conditional for
        MS systems.

        * src/io.c: Include binary-io.h.
        (sip, read_files): Switch file I/O to binary mode and back as
        appropriate, to support binary files on systems that distinguish
        between text and binary I/O.

--- src/io.c~0  2011-08-15 08:24:38.000000000 +0300
+++ src/io.c    2012-05-12 18:55:24.201750000 +0300
@@ -22,6 +22,7 @@
 #include <cmpbuf.h>
 #include <file-type.h>
 #include <xalloc.h>
+#include <binary-io.h>

 /* Rotate an unsigned value to the left.  */
 #define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))
@@ -110,12 +111,25 @@ sip (struct file_data *current, bool ski
       if (! skip_test)
        {
          /* Check first part of file to see if it's a binary file.  */
-
-         /* FIXME: if O_BINARY, this should revert to text mode
-            if the file is not binary.  */
+         bool binary_file;
+         int prev_mode = SET_BINARY (current->desc);

          file_block_read (current, current->bufsize);
-         return binary_file_p (current->buffer, current->buffered);
+         binary_file = binary_file_p (current->buffer, current->buffered);
+         if (prev_mode != O_BINARY)
+           {
+             /* Revert to text mode and seek back to the beginning to
+                reread the file.  Use relative seek, since file
+                descriptors like stdin might not start at offset
+                zero.  */
+
+             if (lseek (current->desc, -current->buffered, SEEK_CUR) == -1)
+               pfatal_with_name (current->name);
+             (void) UNSET_BINARY (current->desc);
+              current->buffered = 0;
+              current->eof = false;
+           }
+         return binary_file;
        }
     }

@@ -761,7 +775,8 @@ read_files (struct file_data filevec[],
     }
   if (appears_binary)
     {
-      /* FIXME: If O_BINARY, this should set both files to binary mode.  */
+      (void) SET_BINARY (filevec[0].desc);
+      (void) SET_BINARY (filevec[1].desc);
       return true;
     }

--- lib/binary-io.h~1   2012-05-12 17:31:43.639250000 +0300
+++ lib/binary-io.h     2012-05-12 18:19:53.842375000 +0300
@@ -26,9 +26,14 @@
 #include <stdio.h>

 /* SET_BINARY (fd);
-   changes the file descriptor fd to perform binary I/O.  */
+   changes the file descriptor fd to perform binary I/O, returns
+   the previous I/O mode.
+
+   UNSET_BINARY (fd);
+   changes the file descriptor fd to perform text I/O, returns
+   the previous I/O mode. */
 #if O_BINARY
-# if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
+# if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__ || defined _WIN32
 #  include <io.h> /* declares setmode() */
 # else
 #  define setmode _setmode
@@ -40,13 +45,15 @@
    /* Avoid putting stdin/stdout in binary mode if it is connected to
       the console, because that would make it impossible for the user
       to interrupt the program through Ctrl-C or Ctrl-Break.  */
-#  define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
+#  define SET_BINARY(fd) (!isatty (fd) ? setmode (fd, O_BINARY) : -1)
 # else
-#  define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
+#  define SET_BINARY(fd) (setmode (fd, O_BINARY))
 # endif
+# define UNSET_BINARY(fd) (setmode (fd, O_TEXT))
 #else
   /* On reasonable systems, binary I/O is the default.  */
-# define SET_BINARY(fd) /* do nothing */ ((void) 0)
+# define SET_BINARY(fd) /* do nothing */ (O_BINARY)
+# define UNSET_BINARY(fd) /* do nothing */ (-1)
 #endif

 #endif /* _BINARY_H */

Sorry, I found 2 subtle mistakes in the patches I sent.  Please use
the ones below instead:

2012-05-12  Eli Zaretskii  <e...@gnu.org>

        * lib/binary-io.h (SET_BINARY) [O_BINARY]: Return the previous mode.
        (UNSET_BINARY): New macro, to reset I/O to text mode.
        (SET_BINARY, UNSET_BINARY): Include _WIN32 in the conditional for
        MS systems.

        * src/io.c: Include binary-io.h.
        (sip, read_files): Switch file I/O to binary mode and back as
        appropriate, to support binary files on systems that distinguish
        between text and binary I/O.

--- src/io.c~0  2011-08-15 08:24:38.000000000 +0300
+++ src/io.c    2012-05-12 18:55:24.201750000 +0300
@@ -22,6 +22,7 @@
 #include <cmpbuf.h>
 #include <file-type.h>
 #include <xalloc.h>
+#include <binary-io.h>

 /* Rotate an unsigned value to the left.  */
 #define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))
@@ -110,12 +111,25 @@ sip (struct file_data *current, bool ski
       if (! skip_test)
        {
          /* Check first part of file to see if it's a binary file.  */
-
-         /* FIXME: if O_BINARY, this should revert to text mode
-            if the file is not binary.  */
+         bool binary_file;
+         int prev_mode = SET_BINARY (current->desc);

          file_block_read (current, current->bufsize);
-         return binary_file_p (current->buffer, current->buffered);
+         binary_file = binary_file_p (current->buffer, current->buffered);
+         if (prev_mode != O_BINARY)
+           {
+             /* Revert to text mode and seek back to the beginning to
+                reread the file.  Use relative seek, since file
+                descriptors like stdin might not start at offset
+                zero.  */
+
+             if (lseek (current->desc, -current->buffered, SEEK_CUR) == -1)
+               pfatal_with_name (current->name);
+             (void) UNSET_BINARY (current->desc);
+              current->buffered = 0;
+              current->eof = false;
+           }
+         return binary_file;
        }
     }

@@ -761,7 +775,8 @@ read_files (struct file_data filevec[],
     }
   if (appears_binary)
     {
-      /* FIXME: If O_BINARY, this should set both files to binary mode.  */
+      (void) SET_BINARY (filevec[0].desc);
+      (void) SET_BINARY (filevec[1].desc);
       return true;
     }

--- lib/binary-io.h~1   2012-05-12 17:31:43.639250000 +0300
+++ lib/binary-io.h     2012-05-12 18:19:53.842375000 +0300
@@ -26,9 +26,14 @@
 #include <stdio.h>

 /* SET_BINARY (fd);
-   changes the file descriptor fd to perform binary I/O.  */
+   changes the file descriptor fd to perform binary I/O, returns
+   the previous I/O mode.
+
+   UNSET_BINARY (fd);
+   changes the file descriptor fd to perform text I/O, returns
+   the previous I/O mode. */
 #if O_BINARY
-# if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
+# if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__ || defined __MINGW32__
 #  include <io.h> /* declares setmode() */
 # else
 #  define setmode _setmode
@@ -40,13 +45,15 @@
    /* Avoid putting stdin/stdout in binary mode if it is connected to
       the console, because that would make it impossible for the user
       to interrupt the program through Ctrl-C or Ctrl-Break.  */
-#  define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
+#  define SET_BINARY(fd) (!isatty (fd) ? setmode (fd, O_BINARY) : O_BINARY)
 # else
-#  define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
+#  define SET_BINARY(fd) (setmode (fd, O_BINARY))
 # endif
+# define UNSET_BINARY(fd) (setmode (fd, O_TEXT))
 #else
   /* On reasonable systems, binary I/O is the default.  */
-# define SET_BINARY(fd) /* do nothing */ ((void) 0)
+# define SET_BINARY(fd) /* do nothing */ (O_BINARY)
+# define UNSET_BINARY(fd) /* do nothing */ (-1)
 #endif

 #endif /* _BINARY_H */

Should be __MINGW32__, obviously.  Sorry.

I can't comment on the rationale of the diffutils/src/io.c change in
http://git.savannah.gnu.org/gitweb/?p=diffutils.git;a=commitdiff;h=91...

But regarding <binary-io.h>, I am unhappy about another macro UNSET_BINARY.
If you need
  1. to reset the value to O_TEXT,
  2. to get the previous value in return,
then I would suggest to use a function

  int setmode (int fd, int o_mode);

exactly like in Cygwin, so that no code is needed on Cygwin.

If we had the chance to design a new API would prefer

  bool set_binary_mode (int fd, bool binary);

but this interface would have no significant advantage over the well-known
Cygwin one.

This change is wrong. The MSVC headers don't unconditionally declare
'setmode' and 'fileno'.

And, please, for consistency with the other codes, use
"defined _WIN32 || defined __WIN32__", not just "defined _WIN32".

Bruno

What is the rationale/benefit for this proposed change?

Bruno

You mean, us it directly, not through a macro?  But then why does
gnulib provide SET_BINARY as a macro?  I'm probably missing something
here.

Using UNSET_BINARY allowed me to avoid any #ifdef's in the application
code.  If I use setmode, then #ifdef's are necessary.

In fact, Diffutils 2.8.7 used precisely such an API.

Yes, that was my mistake.  I changed this to __MINGW32__ in a
followup (MinGW does have io.h that declares 'setmode').

I think this is a moot point, since _WIN32 will be replaced by
__MINGW32__.

Thanks.

MinGW provides 'setmode' whose declaration is in io.h.

But mingw's declaration of 'fileno' in stdio.h is not always enabled
(only if !defined _NO_OLDNAMES). Therefore the #else branch is needed
on mingw.

Bruno

I meant, through a macro or a function, depending on what's easiest on each
platform.

I meant that setmode should be defined, either as a function or as a
function-like macro, on all platforms.

SET_BINARY is a simpler-to-use macro for the simpler cases. Many GNU
programs do things like this:

  if (strcmp (filename, "-") == 0 || strcmp (filename, "/dev/stdin") == 0)
    {
      fp = stdin;
      SET_BINARY (fileno (fp));
    }
  else
    {
      fp = fopen (filename, "rb");
      ...
    }

I prefer a macro or function that takes an additional boolean argument
to another macro.

Bruno

_NO_OLDNAMES is undefined by default.

That's okay, but then io.h should be included anyway, because it
provides the prototype of _setmode as well.  According to MSDN, the
same is true for MSVC.

Like this?

2012-05-12  Eli Zaretskii  <e...@gnu.org>

        * lib/binary-io.h [O_BINARY]: Include io.h on all systems that
        have non-zero O_BINARY.
        (O_TEXT) [!O_BINARY]: Define if not defined.
        (setmode) [!O_BINARY]: Define to do nothing and return O_BINARY.

        * src/io.c: Include binary-io.h.
        (sip, read_files): Switch file I/O to binary mode and back as
        appropriate, to support binary files on systems that distinguish
        between text and binary I/O.

--- src/io.c~0  2011-08-15 08:24:38.000000000 +0300
+++ src/io.c    2012-05-12 22:49:54.561125000 +0300
@@ -22,6 +22,7 @@
 #include <cmpbuf.h>
 #include <file-type.h>
 #include <xalloc.h>
+#include <binary-io.h>

 /* Rotate an unsigned value to the left.  */
 #define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))
@@ -110,12 +111,25 @@ sip (struct file_data *current, bool ski
       if (! skip_test)
        {
          /* Check first part of file to see if it's a binary file.  */
-
-         /* FIXME: if O_BINARY, this should revert to text mode
-            if the file is not binary.  */
+         bool binary_file;
+         int prev_mode = setmode (current->desc, O_BINARY);

          file_block_read (current, current->bufsize);
-         return binary_file_p (current->buffer, current->buffered);
+         binary_file = binary_file_p (current->buffer, current->buffered);
+         if (prev_mode != O_BINARY)
+           {
+             /* Revert to text mode and seek back to the beginning to
+                reread the file.  Use relative seek, since file
+                descriptors like stdin might not start at offset
+                zero.  */
+
+             if (lseek (current->desc, -current->buffered, SEEK_CUR) == -1)
+               pfatal_with_name (current->name);
+             (void) setmode (current->desc, O_TEXT);
+              current->buffered = 0;
+              current->eof = false;
+           }
+         return binary_file;
        }
     }

@@ -761,7 +775,8 @@ read_files (struct file_data filevec[],
     }
   if (appears_binary)
     {
-      /* FIXME: If O_BINARY, this should set both files to binary mode.  */
+      (void) setmode (filevec[0].desc, O_BINARY);
+      (void) setmode (filevec[1].desc, O_BINARY);
       return true;
     }

--- lib/binary-io.h~1   2012-05-12 17:31:43.639250000 +0300
+++ lib/binary-io.h     2012-05-12 22:50:07.217375000 +0300
@@ -28,9 +28,8 @@
 /* SET_BINARY (fd);
    changes the file descriptor fd to perform binary I/O.  */
 #if O_BINARY
-# if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
-#  include <io.h> /* declares setmode() */
-# else
+# include <io.h> /* declares setmode() */
+# if !defined __EMX__ && !defined __DJGPP__ && !defined __CYGWIN__
 #  define setmode _setmode
 #  undef fileno
 #  define fileno _fileno
@@ -46,7 +45,14 @@
 # endif
 #else
   /* On reasonable systems, binary I/O is the default.  */
+# ifndef O_BINARY
+#  define O_BINARY 0
+# endif
+# ifndef O_TEXT
+#  define O_TEXT 0
+# endif
 # define SET_BINARY(fd) /* do nothing */ ((void) 0)
+# define setmode(fd,m)                   (O_BINARY)
 #endif

 #endif /* _BINARY_H */

But it may be defined.

<io.h> is not needed here. When I add a use of setmode() to the unit test,
with the existing code, I do not get a warning about _setmode() being
undeclared - neither with mingw nor with MSVC. (Maybe this is because
<fcntl.h> already includes <io.h>.)

There is no need to change the code to #include a non-POSIX include file.

Bruno

Not needed, see the other mail.

Why? You don't need it in the diffutils change. Additionally, gnulib's
<fcntl.h> already does it.

This part is basically OK, but lacks comments and a unit test.
Here's a proposed patch. It passes all tests on glibc, mingw, MSVC, Cygwin.

2012-05-12  Bruno Haible  <br...@clisp.org>

        binary-io: Define setmode function.
        * lib/binary-io.h (setmode): Define if not defined by the platform.
        (SET_BINARY): Define in terms of setmode always.
        * tests/test-binary-io.c (main): Accept an argument, and test either
        setmode or SET_BINARY depending on the argument.
        * tests/test-binary-io.sh: Invoke test-binary-io twice, with an argument.
        Clean up also t-bin-out0.tmp.

--- lib/binary-io.h.orig        Sat May 12 23:23:39 2012
+++ lib/binary-io.h     Sat May 12 22:23:04 2012
@@ -25,8 +25,9 @@
    so we include it here first.  */
 #include <stdio.h>

-/* SET_BINARY (fd);
-   changes the file descriptor fd to perform binary I/O.  */
+/* setmode (fd, mode)
+   sets the binary/text I/O mode of file descriptor fd to the given mode
+   (must be O_BINARY or O_TEXT) and returns the previous mode.  */
 #if O_BINARY
 # if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
 #  include <io.h> /* declares setmode() */
@@ -35,18 +36,21 @@
 #  undef fileno
 #  define fileno _fileno
 # endif
-# ifdef __DJGPP__
-#  include <unistd.h> /* declares isatty() */
-   /* Avoid putting stdin/stdout in binary mode if it is connected to
-      the console, because that would make it impossible for the user
-      to interrupt the program through Ctrl-C or Ctrl-Break.  */
-#  define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
-# else
-#  define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
-# endif
 #else
-  /* On reasonable systems, binary I/O is the default.  */
-# define SET_BINARY(fd) /* do nothing */ ((void) 0)
+  /* On reasonable systems, binary I/O is the only choice.  */
+# define setmode(fd, mode) ((void) (fd), (void) (mode), O_BINARY)
+#endif
+
+/* SET_BINARY (fd);
+   changes the file descriptor fd to perform binary I/O.  */
+#ifdef __DJGPP__
+# include <unistd.h> /* declares isatty() */
+  /* Avoid putting stdin/stdout in binary mode if it is connected to
+     the console, because that would make it impossible for the user
+     to interrupt the program through Ctrl-C or Ctrl-Break.  */
+# define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
+#else
+# define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
 #endif

 #endif /* _BINARY_H */
--- tests/test-binary-io.c.orig Sat May 12 23:23:39 2012
+++ tests/test-binary-io.c      Sat May 12 22:27:33 2012
@@ -30,26 +30,40 @@
 #include "macros.h"

 int
-main ()
+main (int argc, char *argv[])
 {
   /* Test the O_BINARY macro.  */
   {
     int fd =
-      open ("t-bin-out2.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
+      open ("t-bin-out0.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
     if (write (fd, "Hello\n", 6) < 0)
       exit (1);
     close (fd);
   }
   {
     struct stat statbuf;
-    if (stat ("t-bin-out2.tmp", &statbuf) < 0)
+    if (stat ("t-bin-out0.tmp", &statbuf) < 0)
       exit (1);
     ASSERT (statbuf.st_size == 6);
   }

-  /* Test the SET_BINARY macro.  */
-  SET_BINARY (1);
-  fputs ("Hello\n", stdout);
+  switch (argv[1][0])
+    {
+    case '1':
+      /* Test the setmode() function.  */
+      setmode (1, O_BINARY);
+      fputs ("Hello\n", stdout);
+      break;
+
+    case '2':
+      /* Test the SET_BINARY macro.  */
+      SET_BINARY (1);
+      fputs ("Hello\n", stdout);
+      break;
+
+    default:
+      break;
+    }

   return 0;
 }
--- tests/test-binary-io.sh.orig        Sat May 12 23:23:39 2012
+++ tests/test-binary-io.sh     Sat May 12 22:28:28 2012
@@ -3,9 +3,11 @@
 tmpfiles=""
 trap 'rm -fr $tmpfiles' 1 2 3 15

-tmpfiles="$tmpfiles t-bin-out1.tmp t-bin-out2.tmp"
-./test-binary-io${EXEEXT} > t-bin-out1.tmp || exit 1
-cmp t-bin-out1.tmp t-bin-out2.tmp > /dev/null || exit 1
+tmpfiles="$tmpfiles t-bin-out0.tmp t-bin-out1.tmp t-bin-out2.tmp"
+./test-binary-io${EXEEXT} 1 > t-bin-out1.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out1.tmp > /dev/null || exit 1
+./test-binary-io${EXEEXT} 2 > t-bin-out2.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out2.tmp > /dev/null || exit 1

 rm -fr $tmpfiles

On 05/12/2012 10:41 AM, Bruno Haible wrote:

That would clash with the setmode function defined
in <unistd.h> in FreeBSD etc., which is partly why we
removed this stuff from diffutils.
I agree that it'd be nicer to have a function
with an additional argument.  But I'd rather
not use a name like 'setmode' that clashes with BSD.

'set_binary_mode' would be OK, but wouldn't it
be cleaner to use fcntl?  The standard way to
set and clear O_* flags is fcntl, so shouldn't
it look like this?

    flags = fcntl (fd, F_GETFL);
    fcntl (fd, F_SETFL, flags | O_BINARY);

Thanks for the heads-up. Indeed MacOS X, FreeBSD, NetBSD, Minix all have
the same kind of getmode/setmode functions.

Good. New proposal attached below.

This can't be easily implemented on native Windows. In particular, there
is no way to retrieve the O_APPEND flag. And the read/write flags are
hard to retrieve without making system calls as well.

2012-05-12  Bruno Haible  <br...@clisp.org>

        binary-io: Define set_binary_mode function.
        * lib/binary-io.h (set_binary_mode): New function.
        (SET_BINARY): Define in terms of set_binary_mode.
        * tests/test-binary-io.c (main): Accept an argument, and test either
        set_binary_mode or SET_BINARY depending on the argument.
        * tests/test-binary-io.sh: Invoke test-binary-io twice, with an argument.
        Clean up also t-bin-out0.tmp.

--- lib/binary-io.h.orig        Sun May 13 03:58:11 2012
+++ lib/binary-io.h     Sun May 13 03:57:27 2012
@@ -25,28 +25,33 @@
    so we include it here first.  */
 #include <stdio.h>

-/* SET_BINARY (fd);
-   changes the file descriptor fd to perform binary I/O.  */
+/* set_binary_mode (fd, mode)
+   sets the binary/text I/O mode of file descriptor fd to the given mode
+   (must be O_BINARY or O_TEXT) and returns the previous mode.  */
 #if O_BINARY
 # if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
 #  include <io.h> /* declares setmode() */
+#  define set_binary_mode setmode
 # else
-#  define setmode _setmode
+#  define set_binary_mode _setmode
 #  undef fileno
 #  define fileno _fileno
 # endif
-# ifdef __DJGPP__
-#  include <unistd.h> /* declares isatty() */
-   /* Avoid putting stdin/stdout in binary mode if it is connected to
-      the console, because that would make it impossible for the user
-      to interrupt the program through Ctrl-C or Ctrl-Break.  */
-#  define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
-# else
-#  define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
-# endif
 #else
-  /* On reasonable systems, binary I/O is the default.  */
-# define SET_BINARY(fd) /* do nothing */ ((void) 0)
+  /* On reasonable systems, binary I/O is the only choice.  */
+# define set_binary_mode(fd, mode) ((void) (fd), (void) (mode), O_BINARY)
+#endif
+
+/* SET_BINARY (fd);
+   changes the file descriptor fd to perform binary I/O.  */
+#ifdef __DJGPP__
+# include <unistd.h> /* declares isatty() */
+  /* Avoid putting stdin/stdout in binary mode if it is connected to
+     the console, because that would make it impossible for the user
+     to interrupt the program through Ctrl-C or Ctrl-Break.  */
+# define SET_BINARY(fd) ((void) (!isatty (fd) ? (set_binary_mode (fd, O_BINARY), 0) : 0))
+#else
+# define SET_BINARY(fd) ((void) set_binary_mode (fd, O_BINARY))
 #endif

 #endif /* _BINARY_H */
--- tests/test-binary-io.c.orig Sun May 13 03:58:11 2012
+++ tests/test-binary-io.c      Sun May 13 03:56:50 2012
@@ -30,26 +30,40 @@
 #include "macros.h"

 int
-main ()
+main (int argc, char *argv[])
 {
   /* Test the O_BINARY macro.  */
   {
     int fd =
-      open ("t-bin-out2.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
+      open ("t-bin-out0.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
     if (write (fd, "Hello\n", 6) < 0)
       exit (1);
     close (fd);
   }
   {
     struct stat statbuf;
-    if (stat ("t-bin-out2.tmp", &statbuf) < 0)
+    if (stat ("t-bin-out0.tmp", &statbuf) < 0)
       exit (1);
     ASSERT (statbuf.st_size == 6);
   }

-  /* Test the SET_BINARY macro.  */
-  SET_BINARY (1);
-  fputs ("Hello\n", stdout);
+  switch (argv[1][0])
+    {
+    case '1':
+      /* Test the set_binary_mode() function.  */
+      set_binary_mode (1, O_BINARY);
+      fputs ("Hello\n", stdout);
+      break;
+
+    case '2':
+      /* Test the SET_BINARY macro.  */
+      SET_BINARY (1);
+      fputs ("Hello\n", stdout);
+      break;
+
+    default:
+      break;
+    }

   return 0;
 }
--- tests/test-binary-io.sh.orig        Sun May 13 03:58:11 2012
+++ tests/test-binary-io.sh     Sat May 12 22:28:28 2012
@@ -3,9 +3,11 @@
 tmpfiles=""
 trap 'rm -fr $tmpfiles' 1 2 3 15

-tmpfiles="$tmpfiles t-bin-out1.tmp t-bin-out2.tmp"
-./test-binary-io${EXEEXT} > t-bin-out1.tmp || exit 1
-cmp t-bin-out1.tmp t-bin-out2.tmp > /dev/null || exit 1
+tmpfiles="$tmpfiles t-bin-out0.tmp t-bin-out1.tmp t-bin-out2.tmp"
+./test-binary-io${EXEEXT} 1 > t-bin-out1.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out1.tmp > /dev/null || exit 1
+./test-binary-io${EXEEXT} 2 > t-bin-out2.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out2.tmp > /dev/null || exit 1

 rm -fr $tmpfiles

Yes, I do.  See this line:

              (void) setmode (current->desc, O_TEXT);

Thanks.

And here's the patch for Diffutils' io.c to go with the new proposal:

2012-05-13  Eli Zaretskii  <e...@gnu.org>

        * src/io.c: Include binary-io.h.
        (sip, read_files): Switch file I/O to binary mode and back as
        appropriate, to support binary files on systems that distinguish
        between text and binary I/O.

--- src/io.c~0  2011-08-15 08:24:38.000000000 +0300
+++ src/io.c    2012-05-13 21:38:39.795500000 +0300
@@ -22,6 +22,7 @@
 #include <cmpbuf.h>
 #include <file-type.h>
 #include <xalloc.h>
+#include <binary-io.h>

 /* Rotate an unsigned value to the left.  */
 #define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))
@@ -110,12 +111,25 @@ sip (struct file_data *current, bool ski
       if (! skip_test)
        {
          /* Check first part of file to see if it's a binary file.  */
-
-         /* FIXME: if O_BINARY, this should revert to text mode
-            if the file is not binary.  */
+         bool binary_file;
+         int prev_mode = set_binary_mode (current->desc, O_BINARY);

          file_block_read (current, current->bufsize);
-         return binary_file_p (current->buffer, current->buffered);
+         binary_file = binary_file_p (current->buffer, current->buffered);
+         if (prev_mode != O_BINARY)
+           {
+             /* Revert to text mode and seek back to the beginning to
+                reread the file.  Use relative seek, since file
+                descriptors like stdin might not start at offset
+                zero.  */
+
+             if (lseek (current->desc, -current->buffered, SEEK_CUR) == -1)
+               pfatal_with_name (current->name);
+             (void) set_binary_mode (current->desc, O_TEXT);
+              current->buffered = 0;
+              current->eof = false;
+           }
+         return binary_file;
        }
     }

@@ -761,7 +775,8 @@ read_files (struct file_data filevec[],
     }
   if (appears_binary)
     {
-      /* FIXME: If O_BINARY, this should set both files to binary mode.  */
+      (void) set_binary_mode (filevec[0].desc, O_BINARY);
+      (void) set_binary_mode (filevec[1].desc, O_BINARY);
       return true;
     }

On 05/12/2012 07:00 PM, Bruno Haible wrote:

With that approach, code like this:

   set_binary_mode (current->desc, prev_mode);

yields the following undesirable diagnostic:

   io.c:127:8: error: statement with no effect [-Werror=unused-value]

How about something like the following definition instead?
It would also have the advantage of better type-checking on
POSIX hosts.

static int
set_binary_mode (int fd, int mode)
{
  (void) fd;
  (void) mode;
  return O_BINARY;

OK. Since I don't want all callers to use '(void)' casts, I'm making it
a function, like you say. An inline function, since I don't like to penalize
the compiled code on GNU systems for such no-ops.

Bruno

2012-05-13  Bruno Haible  <br...@clisp.org>
            Paul Eggert  <egg...@cs.ucla.edu>

        binary-io: Define set_binary_mode function.
        * lib/binary-io.h (set_binary_mode): New function.
        (SET_BINARY): Define in terms of set_binary_mode.
        * modules/binary-io (configure.ac): Require AC_C_INLINE.
        * tests/test-binary-io.c (main): Accept an argument, and test either
        set_binary_mode or SET_BINARY depending on the argument.
        * tests/test-binary-io.sh: Invoke test-binary-io twice, with an
        argument. Clean up also t-bin-out0.tmp.

--- lib/binary-io.h.orig        Sun May 13 22:54:11 2012
+++ lib/binary-io.h     Sun May 13 22:51:50 2012
@@ -25,28 +25,41 @@
    so we include it here first.  */
 #include <stdio.h>

-/* SET_BINARY (fd);
-   changes the file descriptor fd to perform binary I/O.  */
+/* set_binary_mode (fd, mode)
+   sets the binary/text I/O mode of file descriptor fd to the given mode
+   (must be O_BINARY or O_TEXT) and returns the previous mode.  */
 #if O_BINARY
 # if defined __EMX__ || defined __DJGPP__ || defined __CYGWIN__
 #  include <io.h> /* declares setmode() */
+#  define set_binary_mode setmode
 # else
-#  define setmode _setmode
+#  define set_binary_mode _setmode
 #  undef fileno
 #  define fileno _fileno
 # endif
-# ifdef __DJGPP__
-#  include <unistd.h> /* declares isatty() */
-   /* Avoid putting stdin/stdout in binary mode if it is connected to
-      the console, because that would make it impossible for the user
-      to interrupt the program through Ctrl-C or Ctrl-Break.  */
-#  define SET_BINARY(fd) ((void) (!isatty (fd) ? (setmode (fd, O_BINARY), 0) : 0))
-# else
-#  define SET_BINARY(fd) ((void) setmode (fd, O_BINARY))
-# endif
 #else
-  /* On reasonable systems, binary I/O is the default.  */
-# define SET_BINARY(fd) /* do nothing */ ((void) 0)
+  /* On reasonable systems, binary I/O is the only choice.  */
+  /* Use an inline function rather than a macro, to avoid gcc warnings
+     "warning: statement with no effect".  */
+static inline int
+set_binary_mode (int fd, int mode)
+{
+  (void) fd;
+  (void) mode;
+  return O_BINARY;
+}
+#endif
+
+/* SET_BINARY (fd);
+   changes the file descriptor fd to perform binary I/O.  */
+#ifdef __DJGPP__
+# include <unistd.h> /* declares isatty() */
+  /* Avoid putting stdin/stdout in binary mode if it is connected to
+     the console, because that would make it impossible for the user
+     to interrupt the program through Ctrl-C or Ctrl-Break.  */
+# define SET_BINARY(fd) ((void) (!isatty (fd) ? (set_binary_mode (fd, O_BINARY), 0) : 0))
+#else
+# define SET_BINARY(fd) ((void) set_binary_mode (fd, O_BINARY))
 #endif

 #endif /* _BINARY_H */
--- modules/binary-io.orig      Sun May 13 22:54:11 2012
+++ modules/binary-io   Sun May 13 22:47:52 2012
@@ -8,6 +8,7 @@
 fcntl-h

 configure.ac:
+AC_REQUIRE([AC_C_INLINE])

 Makefile.am:
 lib_SOURCES += binary-io.h
--- tests/test-binary-io.c.orig Sun May 13 22:54:12 2012
+++ tests/test-binary-io.c      Sun May 13 03:56:50 2012
@@ -30,26 +30,40 @@
 #include "macros.h"

 int
-main ()
+main (int argc, char *argv[])
 {
   /* Test the O_BINARY macro.  */
   {
     int fd =
-      open ("t-bin-out2.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
+      open ("t-bin-out0.tmp", O_CREAT | O_TRUNC | O_RDWR | O_BINARY, 0600);
     if (write (fd, "Hello\n", 6) < 0)
       exit (1);
     close (fd);
   }
   {
     struct stat statbuf;
-    if (stat ("t-bin-out2.tmp", &statbuf) < 0)
+    if (stat ("t-bin-out0.tmp", &statbuf) < 0)
       exit (1);
     ASSERT (statbuf.st_size == 6);
   }

-  /* Test the SET_BINARY macro.  */
-  SET_BINARY (1);
-  fputs ("Hello\n", stdout);
+  switch (argv[1][0])
+    {
+    case '1':
+      /* Test the set_binary_mode() function.  */
+      set_binary_mode (1, O_BINARY);
+      fputs ("Hello\n", stdout);
+      break;
+
+    case '2':
+      /* Test the SET_BINARY macro.  */
+      SET_BINARY (1);
+      fputs ("Hello\n", stdout);
+      break;
+
+    default:
+      break;
+    }

   return 0;
 }
--- tests/test-binary-io.sh.orig        Sun May 13 22:54:12 2012
+++ tests/test-binary-io.sh     Sat May 12 22:28:28 2012
@@ -3,9 +3,11 @@
 tmpfiles=""
 trap 'rm -fr $tmpfiles' 1 2 3 15

-tmpfiles="$tmpfiles t-bin-out1.tmp t-bin-out2.tmp"
-./test-binary-io${EXEEXT} > t-bin-out1.tmp || exit 1
-cmp t-bin-out1.tmp t-bin-out2.tmp > /dev/null || exit 1
+tmpfiles="$tmpfiles t-bin-out0.tmp t-bin-out1.tmp t-bin-out2.tmp"
+./test-binary-io${EXEEXT} 1 > t-bin-out1.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out1.tmp > /dev/null || exit 1
+./test-binary-io${EXEEXT} 2 > t-bin-out2.tmp || exit 1
+cmp t-bin-out0.tmp t-bin-out2.tmp > /dev/null || exit 1

 rm -fr $tmpfiles

Thanks for the diffutils patch.  We're a bit better off with something
even closer to the pre-2006 approach, which took care to convert
size_t to off_t before negating it, as that is important on hosts where
sizeof (size_t) < sizeof (off_t).  Also, it's cleaner to use set_binary_mode
uniformly rather than set_binary_mode sometimes and SET_BINARY others.
Here's a revised patch that I hope catches all the issues.  I plan to
push it after Bruno's binary-io.h patches are pushed.

Use binary mode when testing for binary files.
This reverts the 2006-01-05 change and modernizes to the current API.
Idea suggested by Eli Zaretskii in:
http://lists.gnu.org/archive/html/bug-gnu-utils/2012-05/msg00066.html
* src/cmp.c (main):
* src/diff.c (main, compare_files):
Use set_binary_mode rather than SET_BINARY.
* src/diff.c (compare_files): Omit unnecessary use of O_BINARY.
* src/io.c (sip): Sample unknown files in binary mode, to see
whether they are binary.
(read_files): Read binary files in binary mode.
diff --git a/src/cmp.c b/src/cmp.c
index 1387ec1..32b25e6 100644
--- a/src/cmp.c
+++ b/src/cmp.c
@@ -293,7 +293,7 @@ main (int argc, char **argv)
        {
          file_desc[f1] = STDIN_FILENO;
          if (O_BINARY && ! isatty (STDIN_FILENO))
-           SET_BINARY (STDIN_FILENO);
+           set_binary_mode (STDIN_FILENO, O_BINARY);
        }
       else
        file_desc[f1] = open (file[f1], O_RDONLY | O_BINARY, 0);
diff --git a/src/diff.c b/src/diff.c
index b316afe..79a4726 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -524,7 +524,7 @@ main (int argc, char **argv)
 #if O_BINARY
          binary = true;
          if (! isatty (STDOUT_FILENO))
-           SET_BINARY (STDOUT_FILENO);
+           set_binary_mode (STDOUT_FILENO, O_BINARY);
 #endif
          break;

@@ -1111,8 +1111,8 @@ compare_files (struct comparison const *parent,
          else if (STREQ (cmp.file[f].name, "-"))
            {
              cmp.file[f].desc = STDIN_FILENO;
-             if (O_BINARY && binary && ! isatty (STDIN_FILENO))
-               SET_BINARY (STDIN_FILENO);
+             if (binary && ! isatty (STDIN_FILENO))
+               set_binary_mode (STDIN_FILENO, O_BINARY);
              if (fstat (STDIN_FILENO, &cmp.file[f].stat) != 0)
                cmp.file[f].desc = ERRNO_ENCODE (errno);
              else
diff --git a/src/io.c b/src/io.c
index 5a631a5..3abffb5 100644
--- a/src/io.c
+++ b/src/io.c
@@ -19,6 +19,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 #include "diff.h"
+#include <binary-io.h>
 #include <cmpbuf.h>
 #include <file-type.h>
 #include <xalloc.h>
@@ -111,11 +112,24 @@ sip (struct file_data *current, bool skip_test)
        {
          /* Check first part of file to see if it's a binary file.  */

-         /* FIXME: if O_BINARY, this should revert to text mode
-            if the file is not binary.  */
-
+         int prev_mode = set_binary_mode (current->desc, O_BINARY);
+         off_t buffered;
          file_block_read (current, current->bufsize);
-         return binary_file_p (current->buffer, current->buffered);
+         buffered = current->buffered;
+
+         if (prev_mode != O_BINARY)
+           {
+             /* Revert to text mode and seek back to the start to reread
+                the file.  Use relative seek, since file descriptors
+                like stdin might not start at offset zero.  */
+             if (lseek (current->desc, - buffered, SEEK_CUR) < 0)
+               pfatal_with_name (current->name);
+             set_binary_mode (current->desc, prev_mode);
+             current->buffered = 0;
+             current->eof = false;
+           }
+
+         return binary_file_p (current->buffer, buffered);
        }
     }

@@ -761,7 +775,8 @@ read_files (struct file_data filevec[], bool pretend_binary)
     }
   if (appears_binary)
     {
-      /* FIXME: If O_BINARY, this should set both files to binary mode.  */
+      set_binary_mode (filevec[0].desc, O_BINARY);
+      set_binary_mode (filevec[1].desc, O_BINARY);
       return true;
     }

On 05/12/2012 05:37 PM, Paul Eggert wrote:

No, because cygwin doesn't do it that way.  The only way to change
between O_BINARY and O_TEXT on cygwin is via setmode(), and it is not
worth wrapping fcntl() to make that an alternate interface.

--
Eric Blake   ebl...@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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Works for me, thanks.