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Re: [RFA] error-catching mechanism for scripts
- From: Fernando Nasser <fnasser at redhat dot com>
- To: Don Howard <dhoward at redhat dot com>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Mon, 21 Jan 2002 15:27:52 -0500
- Subject: Re: [RFA] error-catching mechanism for scripts
- Organization: Red Hat , Inc. - Toronto
- References: <Pine.LNX.4.33.0112171700200.18540-100000@theotherone.redhat-remotie.org>
Don,
This is a cool command. Have you ever had the time to address
Andrew's and Eli's suggestions (and a couple of tests)?
Best regards,
Fernando
Don Howard wrote:
>
> Here is an implementation of the error-catcher that I mentioned a few
> weeks ago. I chose "try" and "except" as the keywords:
>
> try
> some commands that might error
> end
>
> -- or --
>
> try
> some commands that might error
> except
> some commands to recover from error
> (errors in this block will not be caught)
> end
>
> I've included a quick write-up for the gdb manual. I'll submit new tests
> for the testsuite shortly.
>
> 2001-12-18 Don Howard <dhoward@redhat.com>
>
> * cli/cli-script.h: New function.
> * cli/cli-script.c (build_command_line): Add support for try
> command.
> (print_command_lines): Ditto.
> (print_command_line): Ditto.
> (execute_control_command): Ditto.
> (read_next_line): Ditto.
> (recurse_read_control_structure): Ditto.
> (captured_execute_control_command): New function.
> (try_command): Ditto.
> * cli/cli-cmds.c (init_cli_cmds): Add try command.
> * defs.h (enum misc_command_type): Added enum except_command.
> (enum command_control_type): Exclude zero from the range of
> command_control_type. Added enum try_control.
>
> 2001-12-18 Don Howard <dhoward@redhat.com>
>
> * gdb.texinfo (User-defined commands): New section, documenting
> try/except feature.
>
> Index: defs.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/defs.h,v
> retrieving revision 1.68
> diff -p -u -w -r1.68 defs.h
> --- defs.h 2001/12/15 16:53:22 1.68
> +++ defs.h 2001/12/18 23:45:33
> @@ -811,16 +811,18 @@ enum misc_command_type
> ok_command,
> end_command,
> else_command,
> + except_command,
> nop_command
> };
>
> enum command_control_type
> {
> - simple_control,
> + simple_control = 1,
> break_control,
> continue_control,
> while_control,
> if_control,
> + try_control,
> invalid_control
> };
>
> Index: cli/cli-cmds.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/cli/cli-cmds.c,v
> retrieving revision 1.10
> diff -p -u -w -r1.10 cli-cmds.c
> --- cli-cmds.c 2001/09/01 21:38:05 1.10
> +++ cli-cmds.c 2001/12/18 23:45:34
> @@ -721,6 +721,12 @@ The conditional expression must follow t
> followed by a new line. The nested commands must be entered one per line,\n\
> and should be terminated by the word `end'.");
>
> + add_com ("try", class_support, try_command,
> +"Execute nested commands. On error, terminate execution of the 'try' block\n\
> +and execute the optional 'except' block. Commands must be entered one per line,\n\
> +terminating with the word 'end'.");
> +
> +
> add_com ("if", class_support, if_command,
> "Execute nested commands once IF the conditional expression is non zero.\n\
> The conditional expression must follow the word `if' and must in turn be\n\
> Index: cli/cli-script.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/cli/cli-script.c,v
> retrieving revision 1.8
> diff -p -u -w -r1.8 cli-script.c
> --- cli-script.c 2001/12/13 22:42:23 1.8
> +++ cli-script.c 2001/12/18 23:45:34
> @@ -83,7 +83,7 @@ build_command_line (enum command_control
> {
> struct command_line *cmd;
>
> - if (args == NULL)
> + if (args == NULL && type != try_control)
> error ("if/while commands require arguments.\n");
>
> cmd = (struct command_line *) xmalloc (sizeof (struct command_line));
> @@ -95,7 +95,12 @@ build_command_line (enum command_control
> = (struct command_line **) xmalloc (sizeof (struct command_line *)
> * cmd->body_count);
> memset (cmd->body_list, 0, sizeof (struct command_line *) * cmd->body_count);
> +
> + if (type != try_control)
> cmd->line = savestring (args, strlen (args));
> + else
> + cmd->line = savestring ("", strlen (""));
> +
> return cmd;
> }
>
> @@ -208,6 +213,33 @@ print_command_lines (struct ui_out *uiou
> continue;
> }
>
> + /* A try command. Recursively print the try and catch blocks
> + before continuing. */
> + if (list->control_type == try_control)
> + {
> + ui_out_field_string (uiout, NULL, "try");
> + ui_out_text (uiout, "\n");
> + /* The true arm. */
> + print_command_lines (uiout, list->body_list[0], depth + 1);
> +
> + /* Show the except arm if it exists. */
> + if (list->body_count == 2)
> + {
> + if (depth)
> + ui_out_spaces (uiout, 2 * depth);
> + ui_out_field_string (uiout, NULL, "except");
> + ui_out_text (uiout, "\n");
> + print_command_lines (uiout, list->body_list[1], depth + 1);
> + }
> +
> + if (depth)
> + ui_out_spaces (uiout, 2 * depth);
> + ui_out_field_string (uiout, NULL, "end");
> + ui_out_text (uiout, "\n");
> + list = list->next;
> + continue;
> + }
> +
> /* ignore illegal command type and try next */
> list = list->next;
> } /* while (list) */
> @@ -290,7 +322,33 @@ print_command_line (struct command_line
> }
> fputs_filtered ("end\n", stream);
> }
> +
> + /* A try command. Recursively print both try and catch blocks. */
> + if (cmd->control_type == try_control)
> + {
> + fputs_filtered ("try\n", stream);
> + /* The true arm. */
> + print_command_line (cmd->body_list[0], depth + 1, stream);
> +
> + /* Show the catch block if it exists. */
> + if (cmd->body_count == 2)
> + {
> + if (depth)
> + {
> + for (i = 0; i < depth; i++)
> + fputs_filtered (" ", stream);
> + }
> + fputs_filtered ("except\n", stream);
> + print_command_line (cmd->body_list[1], depth + 1, stream);
> + }
> + if (depth)
> + {
> + for (i = 0; i < depth; i++)
> + fputs_filtered (" ", stream);
> }
> + fputs_filtered ("end\n", stream);
> + }
> +}
> #endif
>
> /* Execute the command in CMD. */
> @@ -326,6 +384,13 @@ execute_user_command (struct cmd_list_el
> do_cleanups (old_chain);
> }
>
> +static int
> +captured_execute_control_command (PTR arg)
> +{
> + struct command_line * cmd = (struct command_line *) arg;
> + return execute_control_command (cmd);
> +}
> +
> enum command_control_type
> execute_control_command (struct command_line *cmd)
> {
> @@ -459,6 +524,30 @@ execute_control_command (struct command_
> break;
> }
>
> + case try_control:
> + {
> + current = cmd->body_list[0];
> +
> + while (current)
> + {
> + ret = catch_errors (captured_execute_control_command, current,
> + "", RETURN_MASK_ALL);
> +
> + if (ret == 0 || ret == invalid_control)
> + {
> + if (cmd->body_count == 2)
> + current = cmd->body_list[1];
> + else
> + current = NULL;
> + }
> + else
> + {
> + current = current->next;
> + }
> + }
> + break;
> + }
> +
> default:
> warning ("Invalid control type in command structure.");
> return invalid_control;
> @@ -506,6 +595,21 @@ if_command (char *arg, int from_tty)
> free_command_lines (&command);
> }
>
> +void
> +try_command (char *block, int from_tty)
> +{
> + struct command_line *command = NULL;
> +
> + control_level = 1;
> + command = get_command_line (try_control, block);
> +
> + if (command == NULL)
> + return;
> +
> + execute_control_command (command);
> + free_command_lines (&command);
> +}
> +
> /* Cleanup */
> static void
> arg_cleanup (void *ignore)
> @@ -758,12 +862,18 @@ read_next_line (struct command_line **co
> if (p1 - p == 4 && !strncmp (p, "else", 4))
> return else_command;
>
> + /* Is the except clause of an if try structure? */
> + if (p1 - p == 6 && !strncmp (p, "except", 6))
> + return except_command;
> +
> /* Check for while, if, break, continue, etc and build a new command
> line structure for them. */
> if (p1 - p > 5 && !strncmp (p, "while", 5))
> *command = build_command_line (while_control, p + 6);
> else if (p1 - p > 2 && !strncmp (p, "if", 2))
> *command = build_command_line (if_control, p + 3);
> + else if (p1 - p == 3 && !strncmp (p, "try", 3))
> + *command = build_command_line (try_control, p + 4);
> else if (p1 - p == 10 && !strncmp (p, "loop_break", 10))
> {
> *command = (struct command_line *)
> @@ -845,7 +955,8 @@ recurse_read_control_structure (struct c
> if (val == end_command)
> {
> if (current_cmd->control_type == while_control
> - || current_cmd->control_type == if_control)
> + || current_cmd->control_type == if_control
> + || current_cmd->control_type == try_control)
> {
> /* Success reading an entire control structure. */
> ret = simple_control;
> @@ -876,6 +987,23 @@ recurse_read_control_structure (struct c
> }
> }
>
> + if (val == except_command)
> + {
> + if (current_cmd->control_type == try_control
> + && current_body == 1)
> + {
> + realloc_body_list (current_cmd, 2);
> + current_body = 2;
> + child_tail = NULL;
> + continue;
> + }
> + else
> + {
> + ret = invalid_control;
> + break;
> + }
> + }
> +
> if (child_tail)
> {
> child_tail->next = next;
> @@ -895,7 +1023,8 @@ recurse_read_control_structure (struct c
> /* If the latest line is another control structure, then recurse
> on it. */
> if (next->control_type == while_control
> - || next->control_type == if_control)
> + || next->control_type == if_control
> + || next->control_type == try_control)
> {
> control_level++;
> ret = recurse_read_control_structure (next);
> @@ -962,7 +1091,8 @@ read_command_lines (char *prompt_arg, in
> }
>
> if (next->control_type == while_control
> - || next->control_type == if_control)
> + || next->control_type == if_control
> + || next->control_type == try_control)
> {
> control_level++;
> ret = recurse_read_control_structure (next);
> Index: cli/cli-script.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/cli/cli-script.h,v
> retrieving revision 1.2
> diff -p -u -w -r1.2 cli-script.h
> --- cli-script.h 2001/03/06 08:21:20 1.2
> +++ cli-script.h 2001/12/18 23:45:34
> @@ -31,6 +31,8 @@ extern void while_command (char *arg, in
>
> extern void if_command (char *arg, int from_tty);
>
> +extern void try_command (char *block, int from_tty);
> +
> extern void show_user_1 (struct cmd_list_element *c, struct ui_file *stream);
>
> /* Exported to gdb/breakpoint.c */
> Index: doc/gdb.texinfo
> ===================================================================
> RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
> retrieving revision 1.59
> diff -p -u -w -r1.59 gdb.texinfo
> --- gdb.texinfo 2001/11/30 23:03:09 1.59
> +++ gdb.texinfo 2001/12/18 23:45:47
> @@ -13323,6 +13323,17 @@ execute, one per line, terminated by an
> The commands are executed repeatedly as long as the expression
> evaluates to true.
>
> +@kindex try
> +@kindex except
> +@item try
> +Takes no arguments and must be followed by a series of commands to be
> +executed, one per line. Errors in the series of commands will terminate
> +execution of the series, but not the entire script. There can be and
> +optional @code{except} line, which must also be followed by a series of
> +commands, one per line. Commands in the @code{except} block are
> +executed if an error is encountered in the corresponding @code{try}
> +block.
> +
> @kindex document
> @item document @var{commandname}
> Document the user-defined command @var{commandname}, so that it can be
>
> --
> dhoward@redhat.com
> gdb engineering
--
Fernando Nasser
Red Hat - Toronto E-Mail: fnasser@redhat.com
2323 Yonge Street, Suite #300
Toronto, Ontario M4P 2C9