Sync readline/ to version 7.0 alpha

This patch syncs our upstream copy of readline from version 6.2 to the
latest version, 7.0 alpha (released July 10 2015).

I essentially copied what was done the last time readline was synced,
when Jan updated to readline 6.2 in 2011:
http://sourceware.org/ml/gdb-patches/2011-05/msg00003.html

Procedure:

1. I extracted the readline-7.0-alpha tarball on top of readline/.
2. I deleted all the new files under doc/ that were deliberately omitted
   before.
3. I regenerated readline/configure and readline/examples/rlfe/configure
   using autoconf 2.64.  No other configure files need regenerating.
4. I updated the function gdb_printable_part in completer.c with a
   trivial change made to the readline function it is based off of,
   printable_part in readline/complete.c.  There is more work to be done in
   completer.c to sync it with readline/complete.c, but it is non-trivial
   and should probably be done separately anyway.

Local patches that had to be reapplied:

    None.  readline 7.0 alpha contains all of our local readline
    patches.

New files in readline/:

    colors.{c,h}
    examples/{hist_erasedups,hist_purgecmd,rl-callbacktest,rlbasic}.c
    parse-colors.{c,h}
    readline.pc.in
    configure.ac

Deleted files in readline/:

    configure.in

Regressions:

After the sync there is one testsuite regression, the test
"signal SIGINT" in gdb.gdb/selftest.exp which now FAILs.  Previously,
the readline 6.2 SIGINT handler would temporarily reinstall the
underlying application's SIGINT handler and immediately re-raise SIGINT
so that the orginal handler gets invoked.  But now (since readline 6.3)
its SIGINT handler does not re-raise SIGINT or directly invoke the
original handler; it now sets a flag marking that SIGINT was raised, and
waits until readline explicitly has control to call the application's
SIGINT handler.  Anyway, because SIGINT is no longer re-raised from
within readline's SIGINT handler, doing "signal SIGINT" with a stopped
inferior gdb process will no longer resume and then immediately stop the
process (since there is no 2nd SIGINT to immediately catch).  Instead,
the inferior gdb process will now just print "Quit" and continue to run.
So with this commit, this particular test case is adjusted to reflect
this change in behavior (we now have to send a 2nd SIGINT manually to
stop it).

Aside from this one testsuite regression, I personally noticed no
regression in user-visible behavior.  Though I only tested on x86_64
and on i686 Debian Stretch.

Getting this kind of change in at the start of the GDB 7.11 development
cycle will allow us to get a lot of passive testing from developers and
from bleeding-edge users.

readline/ChangeLog.gdb:

	Import readline 7.0 alpha
	* configure: Regenerate.
	* examples/rlfe/configure: Regenerate.

gdb/ChangeLog:

	* completer.c (gdb_printable_part): Sync with readline function
	it is based off of.

gdb/testsuite/ChangeLog:

	* gdb.gdb/selftest.exp (test_with_self): Update test to now
	expect the GDB inferior to no longer immediately stop after
	being resumed with "signal SIGINT".

readline/histfile.c

@@ -1,6 +1,6 @@
 /* histfile.c - functions to manipulate the history file. */
 
-/* Copyright (C) 1989-2010 Free Software Foundation, Inc.
+/* Copyright (C) 1989-2015 Free Software Foundation, Inc.
 
    This file contains the GNU History Library (History), a set of
    routines for managing the text of previously typed lines.
@@ -35,6 +35,10 @@
 
 #include <stdio.h>
 
+#if defined (HAVE_LIMITS_H)
+#  include <limits.h>
+#endif
+
 #include <sys/types.h>
 #if ! defined (_MINIX) && defined (HAVE_SYS_FILE_H)
 #  include <sys/file.h>
@@ -99,12 +103,31 @@ extern int errno;
 #include "rlshell.h"
 #include "xmalloc.h"
 
+#if !defined (PATH_MAX)
+#  define PATH_MAX	1024	/* default */
+#endif
+
 /* If non-zero, we write timestamps to the history file in history_do_write() */
 int history_write_timestamps = 0;
 
+/* Immediately after a call to read_history() or read_history_range(), this
+   will return the number of lines just read from the history file in that
+   call. */
+int history_lines_read_from_file = 0;
+
+/* Immediately after a call to write_history() or history_do_write(), this
+   will return the number of lines just written to the history file in that
+   call.  This also works with history_truncate_file. */
+int history_lines_written_to_file = 0;
+
 /* Does S look like the beginning of a history timestamp entry?  Placeholder
    for more extensive tests. */
-#define HIST_TIMESTAMP_START(s)		(*(s) == history_comment_char && isdigit ((s)[1]) )
+#define HIST_TIMESTAMP_START(s)		(*(s) == history_comment_char && isdigit ((unsigned char)(s)[1]) )
+
+static char *history_backupfile PARAMS((const char *));
+static char *history_tempfile PARAMS((const char *));
+static int histfile_backup PARAMS((const char *, const char *));
+static int histfile_restore PARAMS((const char *, const char *));
 
 /* Return the string that should be used in the place of this
    filename.  This only matters when you don't specify the
@@ -123,16 +146,13 @@ history_filename (filename)
     return (return_val);
   
   home = sh_get_env_value ("HOME");
+#if defined (_WIN32)
+  if (home == 0)
+    home = sh_get_env_value ("APPDATA");
+#endif
 
   if (home == 0)
-    {
-#if 0
-      home = ".";
-      home_len = 1;
-#else
-      return (NULL);
-#endif
-    }
+    return (NULL);
   else
     home_len = strlen (home);
 
@@ -148,6 +168,75 @@ history_filename (filename)
   return (return_val);
 }
 
+static char *
+history_backupfile (filename)
+     const char *filename;
+{
+  const char *fn;
+  char *ret, linkbuf[PATH_MAX+1];
+  size_t len;
+  ssize_t n;
+  struct stat fs;
+
+  fn = filename;  
+#if defined (HAVE_READLINK)
+  /* Follow symlink to avoid backing up symlink itself; call will fail if
+     not a symlink */
+  if ((n = readlink (filename, linkbuf, sizeof (linkbuf) - 1)) > 0)
+    {
+      linkbuf[n] = '\0';
+      fn = linkbuf;
+    }
+#endif
+      
+  len = strlen (fn);
+  ret = xmalloc (len + 2);
+  strcpy (ret, fn);
+  ret[len] = '-';
+  ret[len+1] = '\0';
+  return ret;
+}
+  
+static char *
+history_tempfile (filename)
+     const char *filename;
+{
+  const char *fn;
+  char *ret, linkbuf[PATH_MAX+1];
+  size_t len;
+  ssize_t n;
+  struct stat fs;
+  int pid;
+
+  fn = filename;  
+#if defined (HAVE_READLINK)
+  /* Follow symlink so tempfile created in the same directory as any symlinked
+     history file; call will fail if not a symlink */
+  if ((n = readlink (filename, linkbuf, sizeof (linkbuf) - 1)) > 0)
+    {
+      linkbuf[n] = '\0';
+      fn = linkbuf;
+    }
+#endif
+      
+  len = strlen (fn);
+  ret = xmalloc (len + 11);
+  strcpy (ret, fn);
+
+  pid = (int)getpid ();
+
+  /* filename-PID.tmp */
+  ret[len] = '-';
+  ret[len+1] = (pid / 10000 % 10) + '0';
+  ret[len+2] = (pid / 1000 % 10) + '0';
+  ret[len+3] = (pid / 100 % 10) + '0';
+  ret[len+4] = (pid / 10 % 10) + '0';
+  ret[len+5] = (pid % 10) + '0';
+  strcpy (ret + len + 6, ".tmp");
+
+  return ret;
+}
+  
 /* Add the contents of FILENAME to the history list, a line at a time.
    If FILENAME is NULL, then read from ~/.history.  Returns 0 if
    successful, or errno if not. */
@@ -181,6 +270,8 @@ read_history_range (filename, from, to)
   int overflow_errno = EIO;
 #endif
 
+  history_lines_read_from_file = 0;
+
   buffer = last_ts = (char *)NULL;
   input = history_filename (filename);
   file = input ? open (input, O_RDONLY|O_BINARY, 0666) : -1;
@@ -293,6 +384,8 @@ read_history_range (filename, from, to)
 	line_start = line_end + 1;
       }
 
+  history_lines_read_from_file = current_line;
+
   FREE (input);
 #ifndef HISTORY_USE_MMAP
   FREE (buffer);
@@ -303,23 +396,68 @@ read_history_range (filename, from, to)
   return (0);
 }
 
+/* Save FILENAME to BACK, handling case where FILENAME is a symlink
+   (e.g., ~/.bash_history -> .histfiles/.bash_history.$HOSTNAME) */
+static int
+histfile_backup (filename, back)
+     const char *filename;
+     const char *back;
+{
+#if defined (HAVE_READLINK)
+  char linkbuf[PATH_MAX+1];
+  ssize_t n;
+
+  /* Follow to target of symlink to avoid renaming symlink itself */
+  if ((n = readlink (filename, linkbuf, sizeof (linkbuf) - 1)) > 0)
+    {
+      linkbuf[n] = '\0';
+      return (rename (linkbuf, back));
+    }
+#endif
+  return (rename (filename, back));
+}
+
+/* Restore ORIG from BACKUP handling case where ORIG is a symlink
+   (e.g., ~/.bash_history -> .histfiles/.bash_history.$HOSTNAME) */
+static int
+histfile_restore (backup, orig)
+     const char *backup;
+     const char *orig;
+{
+#if defined (HAVE_READLINK)
+  char linkbuf[PATH_MAX+1];
+  ssize_t n;
+
+  /* Follow to target of symlink to avoid renaming symlink itself */
+  if ((n = readlink (orig, linkbuf, sizeof (linkbuf) - 1)) > 0)
+    {
+      linkbuf[n] = '\0';
+      return (rename (backup, linkbuf));
+    }
+#endif
+  return (rename (backup, orig));
+}
+
 /* Truncate the history file FNAME, leaving only LINES trailing lines.
-   If FNAME is NULL, then use ~/.history.  Returns 0 on success, errno
-   on failure. */
+   If FNAME is NULL, then use ~/.history.  Writes a new file and renames
+   it to the original name.  Returns 0 on success, errno on failure. */
 int
 history_truncate_file (fname, lines)
      const char *fname;
      int lines;
 {
-  char *buffer, *filename, *bp, *bp1;		/* bp1 == bp+1 */
-  int file, chars_read, rv;
+  char *buffer, *filename, *tempname, *bp, *bp1;		/* bp1 == bp+1 */
+  int file, chars_read, rv, orig_lines, exists;
   struct stat finfo;
   size_t file_size;
 
+  history_lines_written_to_file = 0;
+
   buffer = (char *)NULL;
   filename = history_filename (fname);
+  tempname = 0;
   file = filename ? open (filename, O_RDONLY|O_BINARY, 0666) : -1;
-  rv = 0;
+  rv = exists = 0;
 
   /* Don't try to truncate non-regular files. */
   if (file == -1 || fstat (file, &finfo) == -1)
@@ -329,6 +467,7 @@ history_truncate_file (fname, lines)
 	close (file);
       goto truncate_exit;
     }
+  exists = 1;
 
   if (S_ISREG (finfo.st_mode) == 0)
     {
@@ -360,6 +499,7 @@ history_truncate_file (fname, lines)
   buffer = (char *)malloc (file_size + 1);
   if (buffer == 0)
     {
+      rv = errno;
       close (file);
       goto truncate_exit;
     }
@@ -373,6 +513,7 @@ history_truncate_file (fname, lines)
       goto truncate_exit;
     }
 
+  orig_lines = lines;
   /* Count backwards from the end of buffer until we have passed
      LINES lines.  bp1 is set funny initially.  But since bp[1] can't
      be a comment character (since it's off the end) and *bp can't be
@@ -401,27 +542,56 @@ history_truncate_file (fname, lines)
 
   /* Write only if there are more lines in the file than we want to
      truncate to. */
-  if (bp > buffer && ((file = open (filename, O_WRONLY|O_TRUNC|O_BINARY, 0600)) != -1))
+  if (bp <= buffer)
     {
-      write (file, bp, chars_read - (bp - buffer));
-
-#if defined (__BEOS__)
-      /* BeOS ignores O_TRUNC. */
-      ftruncate (file, chars_read - (bp - buffer));
-#endif
-
-      close (file);
+      rv = 0;
+      /* No-op if LINES == 0 at this point */
+      history_lines_written_to_file = orig_lines - lines;
+      goto truncate_exit;
     }
 
- truncate_exit:
+  tempname = history_tempfile (filename);
 
+  if ((file = open (tempname, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0600)) != -1)
+    {
+      if (write (file, bp, chars_read - (bp - buffer)) < 0)
+	rv = errno;
+
+      if (close (file) < 0 && rv == 0)
+	rv = errno;
+    }
+  else
+    rv = errno;
+
+ truncate_exit:
   FREE (buffer);
 
+  history_lines_written_to_file = orig_lines - lines;
+
+  if (rv == 0 && filename && tempname)
+    rv = histfile_restore (tempname, filename);
+
+  if (rv != 0)
+    {
+      if (tempname)
+	unlink (tempname);
+      history_lines_written_to_file = 0;
+    }
+
+  /* Make sure the new filename is owned by the same user as the old.  If one
+     user is running this, it's a no-op.  If the shell is running after sudo
+     with a shared history file, we don't want to leave the history file
+     owned by root. */
+  if (rv == 0 && exists)
+    chown (filename, finfo.st_uid, finfo.st_gid);
+
   xfree (filename);
+  FREE (tempname);
+
   return rv;
 }
 
-/* Workhorse function for writing history.  Writes NELEMENT entries
+/* Workhorse function for writing history.  Writes the last NELEMENT entries
    from the history list to FILENAME.  OVERWRITE is non-zero if you
    wish to replace FILENAME with the entries. */
 static int
@@ -430,23 +600,32 @@ history_do_write (filename, nelements, overwrite)
      int nelements, overwrite;
 {
   register int i;
-  char *output;
-  int file, mode, rv;
+  char *output, *tempname, *histname;
+  int file, mode, rv, exists;
+  struct stat finfo;
 #ifdef HISTORY_USE_MMAP
   size_t cursize;
 
+  history_lines_written_to_file = 0;
+
   mode = overwrite ? O_RDWR|O_CREAT|O_TRUNC|O_BINARY : O_RDWR|O_APPEND|O_BINARY;
 #else
   mode = overwrite ? O_WRONLY|O_CREAT|O_TRUNC|O_BINARY : O_WRONLY|O_APPEND|O_BINARY;
 #endif
-  output = history_filename (filename);
+  histname = history_filename (filename);
+  tempname = (overwrite && histname) ? history_tempfile (histname) : 0;
+  output = tempname ? tempname : histname;
+  exists = histname ? (stat (histname, &finfo) == 0) : 0;
+
   file = output ? open (output, mode, 0600) : -1;
   rv = 0;
 
   if (file == -1)
     {
-      FREE (output);
-      return (errno);
+      rv = errno;
+      FREE (histname);
+      FREE (tempname);
+      return (rv);
     }
 
 #ifdef HISTORY_USE_MMAP
@@ -486,8 +665,11 @@ history_do_write (filename, nelements, overwrite)
       {
 mmap_error:
 	rv = errno;
-	FREE (output);
 	close (file);
+	if (tempname)
+	  unlink (tempname);
+	FREE (histname);
+	FREE (tempname);
 	return rv;
       }
 #else    
@@ -495,8 +677,11 @@ mmap_error:
     if (buffer == 0)
       {
       	rv = errno;
-	FREE (output);
 	close (file);
+	if (tempname)
+	  unlink (tempname);
+	FREE (histname);
+	FREE (tempname);
 	return rv;
       }
 #endif
@@ -515,7 +700,7 @@ mmap_error:
       }
 
 #ifdef HISTORY_USE_MMAP
-    if (msync (buffer, buffer_size, 0) != 0 || munmap (buffer, buffer_size) != 0)
+    if (msync (buffer, buffer_size, MS_ASYNC) != 0 || munmap (buffer, buffer_size) != 0)
       rv = errno;
 #else
     if (write (file, buffer, buffer_size) < 0)
@@ -524,9 +709,30 @@ mmap_error:
 #endif
   }
 
-  close (file);
+  history_lines_written_to_file = nelements;
 
-  FREE (output);
+  if (close (file) < 0 && rv == 0)
+    rv = errno;
+
+  if (rv == 0 && histname && tempname)
+    rv = histfile_restore (tempname, histname);
+
+  if (rv != 0)
+    {
+      if (tempname)
+	unlink (tempname);
+      history_lines_written_to_file = 0;
+    }
+
+  /* Make sure the new filename is owned by the same user as the old.  If one
+     user is running this, it's a no-op.  If the shell is running after sudo
+     with a shared history file, we don't want to leave the history file
+     owned by root. */
+  if (rv == 0 && exists)
+    chown (histname, finfo.st_uid, finfo.st_gid);
+
+  FREE (histname);
+  FREE (tempname);
 
   return (rv);
 }