gdb: split apart two different types of filename completion

Unfortunately we have two different types of filename completion in
GDB.

The majority of commands have what I call unquoted filename
completion, this is for commands like 'set logging file ...', 'target
core ...', and 'add-auto-load-safe-path ...'.  For these commands
everything after the command name (that is not a command option) is
treated as a single filename.  If the filename contains white space
then this does not need to be escaped, nor does the filename need to
be quoted.  In fact, the filename argument is not de-quoted, and does
not have any escaping removed, so if a user does try to add such
things, they will be treated as part of the filename.  As an example:

  (gdb) target core "/path/that contains/some white space"

Will look for a directory calls '"' (double quotes) in the local
directory.

A small number of commands do de-quote and remove escapes from
filename arguments.  These command accept what I call quoted and
escaped filenames.  Right now these are the commands that specify the
file for GDB to debug, so:

  file
  exec-file
  symbol-file
  add-symbol-file
  remove-symbol-file

As an example of this in action:

  (gdb) file "/path/that contains/some white space"

In this case GDB would load the file:

  /path/that contains/some white space

Current filename completion always assumes that filenames can be
quoted, though escaping doesn't work in completion right now.  But the
assumption that quoting is allowed is clearly wrong.

This commit splits filename completion into two.  The existing
filename_completer is retained, and is used for unquoted filenames.  A
second filename_maybe_quoted_completer is added which can be used for
completing quoted filenames.

The filename completion test has been extended to cover more cases.
As part of the extended testing I need to know the character that
should be used to separate filenames within a path.  For this TCL 8.6+
has $::tcl_platform(pathSeparator).  To support older versions of TCL
I've added some code to testsuite/lib/gdb.exp.

You might notice that after this commit the completion for unquoted
files is all done in the brkchars phase, that is the function
filename_completer_handle_brkchars calculates the completions and
marks the completion_tracker as using a custom word point.  The reason
for this is that we don't want to break on white space for this
completion, but if we rely on readline to find the completion word,
readline will consider the entire command line, and with no white
space in the word break character set, readline will end up using the
entire command line as the word to complete.

For now at least, the completer for quoted filenames does generate its
completions during the completion phase, though this is going to
change in a later commit.

1 files changed, 2 insertions, 2 deletions

diff --git a/gdb/symfile.c b/gdb/symfile.c
index cf7ab0b..c3cd961 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -3814,7 +3814,7 @@ Usage: symbol-file [-readnow | -readnever] [-o OFF] FILE\n\
 OFF is an optional offset which is added to each section address.\n\
 The `file' command can also load symbol tables, as well as setting the file\n\
 to execute.\n" READNOW_READNEVER_HELP), &cmdlist);
-  set_cmd_completer (c, filename_completer);
+  set_cmd_completer (c, filename_maybe_quoted_completer);
 
   c = add_cmd ("add-symbol-file", class_files, add_symbol_file_command, _("\
 Load symbols from FILE, assuming FILE has been dynamically loaded.\n\
@@ -3828,7 +3828,7 @@ OFF is an optional offset which is added to the default load addresses\n\
 of all sections for which no other address was specified.\n"
 READNOW_READNEVER_HELP),
 	       &cmdlist);
-  set_cmd_completer (c, filename_completer);
+  set_cmd_completer (c, filename_maybe_quoted_completer);
 
   c = add_cmd ("remove-symbol-file", class_files,
 	       remove_symbol_file_command, _("\