[PATCH 1/3] Expand "show disassembler-options" output

[Tom Tromey <tom@tromey.com>]

I typed this:

    (gdb) help set disassembler-options
    Set the disassembler options.
    Usage: set disassembler-options OPTION [,OPTION]...

    See: 'show disassembler-options' for valid option values.

... so I tried what it said and got:

    (gdb) show disassembler-options
    The current disassembler options are ''

This surprised me a little, so this patch adds some text to explain
the situation when an architecture does not have disassembler options.

While there I noticed one more spot where gdb was not using the GNU
style for metasyntactic variables.  This patch fixes this as well.

gdb/ChangeLog
2018-09-14  Tom Tromey  <tom@tromey.com>

	* disasm.c (show_disassembler_options_sfunc): Use GNU style for
	metasyntactic variables.  Print message if no disassembler options
	are available.
---
 gdb/ChangeLog | 6 ++++++
 gdb/disasm.c  | 9 +++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/gdb/disasm.c b/gdb/disasm.c
index 11793df67c0..d908af3fb43 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -1014,13 +1014,18 @@ show_disassembler_options_sfunc (struct ui_file *file, int from_tty,
   valid_options_and_args = gdbarch_valid_disassembler_options (gdbarch);
 
   if (valid_options_and_args == NULL)
-    return;
+    {
+      fputs_filtered (_("(There are no disassembler options available "
+			"for this architecture.)\n"),
+		      file);
+      return;
+    }
 
   valid_options = &valid_options_and_args->options;
 
   fprintf_filtered (file, _("\n\
 The following disassembler options are supported for use with the\n\
-'set disassembler-options <option>[,<option>...]' command:\n"));
+'set disassembler-options OPTION [,OPTION]...' command:\n"));
 
   if (valid_options->description != NULL)
     {
-- 
2.17.1