Re: [RFA 2/2] Add "undefined-command" error code at end of ^error result...

Joel Brobecker
2013-11-20T02:59:35Z

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On Tue, Nov 19, 2013 at 11:13:30AM +0000, Pedro Alves wrote:
> On 11/18/2013 05:11 PM, Joel Brobecker wrote:
>
> > gdb/ChangeLog:
> >
> > (from Pedro Alves <palves@redhat.com>)
> > (from Joel Brobecker <brobecker@adacore.com>)
> > * exceptions.h (enum_errors) <UNKNOWN_COMMAND_ERROR>: New enum.
> > * mi/mi-parse.c (mi_parse): Thow UNKNOWN_COMMAND_ERROR instead
>
> "Throw"
>
> > of a regular error when the GDB/MI command does not exist.
> > * mi/mi-main.c (mi_cmd_list_features): Add
> > "undefined-command-error-code".
> > (mi_print_exception): Print an "undefined-command"
> > error code if EXCEPTION.ERROR in UNKNOWN_COMMAND_ERROR.
>
> s/in/is ?
>
> > * NEWS: Add entry documenting the new "code" variable in
> > "^error" result records.
> >
> > gdb/doc/ChangeLog:
> >
> > * gdb.texinfo (GDB/MI Result Records): Fix the syntax of the
> > "^error" result record concerning the error message. Document
> > the error code that may also be part of that result record.
> > (GDB/MI Miscellaneous Commands): Document the
> > "undefined-command-error-code" element in the output of
> > the "-list-features" GDB/MI command.
> >
> > gdb/testsuite/ChangeLog:
> >
> > * gdb.mi/mi-undefined-cmd.exp: New testcase.
> >
> > Tested on x86_64-linux. OK to commit?
>
> Looks good to me...

Thanks, Pedro! I've made the corrections for the errors you spotted.
And for the UNKNOWN_COMMAND_ERROR vs UNDEFINED_COMMAND_ERROR, I had
already made the changes in the first re-send, for the documentation
fixes.

This patch depends on patch #1, not logically, but there are conflicts
areas that I'd rather not have to deal with if I don't have to. I am
just hoping for someone to review the patch (hint, hint! :-)). If it
takes too much time, I will put this one in first.

--
Joel

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From 902182d958a76a09d9a551c5121fe15e10d2d5bc Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Mon, 18 Nov 2013 16:55:16 +0400
Subject: [PATCH 2/2] Add "undefined-command" error code at end of ^error
result...

... when trying to execute an undefined GDB/MI command. When trying
to execute a GDB/MI command which does not exist, the current error
result record looks like this:

-unsupported
^error,msg="Undefined MI command: unsupported"

The only indication that the command does not exist is the error
message. It would be a little fragile for a consumer to rely solely
on the contents of the error message in order to determine whether
a command exists or not.

This patch improves the situation by adding concept of error
code, starting with one well-defined error code ("undefined-command")
identifying errors due to a non-existant command. Here is the new
output:

-unsupported
^error,msg="Undefined MI command: unsupported",code="undefined-command"

This error code is only displayed when the corresponding error
condition is met. Otherwise, the error record remains unchanged.
For instance:

-symbol-list-lines foo.adb
^error,msg="-symbol-list-lines: Unknown source file name."

For frontends to be able to know whether they can rely on this
variable, a new entry "undefined-command-error-code" has been
added to the "-list-features" command. Another option would be
to always generate an error="..." variable (for the default case,
we could decide for instance that the error code is the empty string).
But it seems more efficient to provide that info in "-list-features"
and then only add the error code when meaningful.

gdb/ChangeLog:

(from Pedro Alves <palves@redhat.com>)
(from Joel Brobecker <brobecker@adacore.com>)
* exceptions.h (enum_errors) <UNDEFINED_COMMAND_ERROR>: New enum.
* mi/mi-parse.c (mi_parse): Throw UNDEFINED_COMMAND_ERROR instead
of a regular error when the GDB/MI command does not exist.
* mi/mi-main.c (mi_cmd_list_features): Add
"undefined-command-error-code".
(mi_print_exception): Print an "undefined-command"
error code if EXCEPTION.ERROR is UNDEFINED_COMMAND_ERROR.
* NEWS: Add entry documenting the new "code" variable in
"^error" result records.

gdb/doc/ChangeLog:

* gdb.texinfo (GDB/MI Result Records): Fix the syntax of the
"^error" result record concerning the error message. Document
the error code that may also be part of that result record.
(GDB/MI Miscellaneous Commands): Document the
"undefined-command-error-code" element in the output of
the "-list-features" GDB/MI command.

gdb/testsuite/ChangeLog:

* gdb.mi/mi-undefined-cmd.exp: New testcase.
---
gdb/NEWS | 6 ++++++
gdb/doc/gdb.texinfo | 19 +++++++++++++++---
gdb/exceptions.h | 3 +++
gdb/mi/mi-main.c | 12 ++++++++++-
gdb/mi/mi-parse.c | 3 ++-
gdb/testsuite/gdb.mi/mi-undefined-cmd.exp | 33 +++++++++++++++++++++++++++++++
6 files changed, 71 insertions(+), 5 deletions(-)
create mode 100644 gdb/testsuite/gdb.mi/mi-undefined-cmd.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index e61c79f..8ef03d6 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -156,6 +156,12 @@ show startup-with-shell
** The new command -info-gdb-mi-command allows the user to determine
whether a GDB/MI command is supported or not.

+ ** The "^error" result record returned when trying to execute an undefined
+ GDB/MI command now provides a variable named "code" whose content is the
+ "undefined-command" error code. Support for this feature can be verified
+ by using the "-list-features" command, which should contain
+ "undefined-command-error-code".
+
** The -trace-save MI command can optionally save trace buffer in Common
Trace Format now.

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 41856b4..4aef805 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -29315,10 +29315,19 @@ which threads are resumed.
@findex ^connected
@value{GDBN} has connected to a remote target.

-@item "^error" "," @var{c-string}
+@item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
@findex ^error
-The operation failed. The @code{@var{c-string}} contains the corresponding
-error message.
+The operation failed. The @code{msg=@var{c-string}} variable contains
+the corresponding error message.
+
+If present, the @code{code=@var{c-string}} variable provides an error
+code on which consumers can rely on to detect the corresponding
+error condition. At present, only one error code is defined:
+
+@table @samp
+@item "undefined-command"
+Indicates that the command causing the error does not exist.
+@end table

@item "^exit"
@findex ^exit
@@ -35175,6 +35184,10 @@ Indicates that all @sc{gdb/mi} commands accept the @option{--language}
option (@pxref{Context management}).
@item info-gdb-mi-command
Indicates support for the @code{-info-gdb-mi-command} command.
+@item undefined-command-error-code
+Indicates support for the "undefined-command" error code in error result
+records, produced when trying to execute an undefined @sc{gdb/mi} command
+(@pxref{GDB/MI Result Records}).
@end table

@subheading The @code{-list-target-features} Command
diff --git a/gdb/exceptions.h b/gdb/exceptions.h
index 129d29a..a3a28f4 100644
--- a/gdb/exceptions.h
+++ b/gdb/exceptions.h
@@ -93,6 +93,9 @@ enum errors {
aborted as the inferior state is no longer valid. */
TARGET_CLOSE_ERROR,

+ /* An undefined command was executed. */
+ UNDEFINED_COMMAND_ERROR,
+
/* Add more errors here. */
NR_ERRORS
};
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 48c8d09..3a0e6a8 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -1818,6 +1818,7 @@ mi_cmd_list_features (char *command, char **argv, int argc)
ui_out_field_string (uiout, NULL, "ada-exceptions");
ui_out_field_string (uiout, NULL, "language-option");
ui_out_field_string (uiout, NULL, "info-gdb-mi-command");
+ ui_out_field_string (uiout, NULL, "undefined-command-error-code");

#if HAVE_PYTHON
if (gdb_python_initialized)
@@ -2023,7 +2024,16 @@ mi_print_exception (const char *token, struct gdb_exception exception)
fputs_unfiltered ("unknown error", raw_stdout);
else
fputstr_unfiltered (exception.message, '"', raw_stdout);
- fputs_unfiltered ("\"\n", raw_stdout);
+ fputs_unfiltered ("\"", raw_stdout);
+
+ switch (exception.error)
+ {
+ case UNDEFINED_COMMAND_ERROR:
+ fputs_unfiltered (",code=\"undefined-command\"", raw_stdout);
+ break;
+ }
+
+ fputs_unfiltered ("\n", raw_stdout);
}

void
diff --git a/gdb/mi/mi-parse.c b/gdb/mi/mi-parse.c
index a2634f1..a092759 100644
--- a/gdb/mi/mi-parse.c
+++ b/gdb/mi/mi-parse.c
@@ -285,7 +285,8 @@ mi_parse (const char *cmd, char **token)
/* Find the command in the MI table. */
parse->cmd = mi_lookup (parse->command);
if (parse->cmd == NULL)
- error (_("Undefined MI command: %s"), parse->command);
+ throw_error (UNDEFINED_COMMAND_ERROR,
+ _("Undefined MI command: %s"), parse->command);

/* Skip white space following the command. */
chp = skip_spaces_const (chp);
diff --git a/gdb/testsuite/gdb.mi/mi-undefined-cmd.exp b/gdb/testsuite/gdb.mi/mi-undefined-cmd.exp
new file mode 100644
index 0000000..8df0a76
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi-undefined-cmd.exp
@@ -0,0 +1,33 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+gdb_exit
+if [mi_gdb_start] {
+ continue
+}
+
+
+# First, verify that the debugger correctly advertises support
+# for the "undefined-command" error code...
+mi_gdb_test "-list-features" \
+ "\\^done,features=\\\[.*\"undefined-command-error-code\".*\\\]" \
+ "-list-features should include \"undefined-command-error-code\""
+
+mi_gdb_test "-undefined-command" \
+ "\\^error,.*,code=\"undefined-command\"" \
+ "error code when executing undefined command"
--
1.8.1.2