[PATCH] init-if-undefined command

[PATCH] init-if-undefined command

[Andrew STUBBS]

[-- Attachment #1: Type: text/plain, Size: 618 bytes --]

Hi,

I have decided that, instead of queuing all my patches here while 
waiting for the current ones to go through, I shall post them all now. 
Hopefully the low hanging fruit will then get done and only the most 
controversial ones will remain when I go away for Christmas.

The attached patch adds a new CLI command named 'init-if-undefined'.

This is essentially the same a 'set variable' (for convenience variables 
only), but does not set the variable if it already has a value.

It is useful in scripts whose values can be overridden, or as an 
approximation of a statically initialised variable.

Andrew Stubbs

[-- Attachment #2: init-if-undefined.patch --]
[-- Type: text/plain, Size: 3560 bytes --]

2005-11-16  Andrew Stubbs  <andrew.stubbs@st.com>

	* value.c (init_if_undefined_command): New function.
	(_initialize_values): Add command init-if-undefined.

doc/
	* gdb.texinfo (Convenience variables): Add init-if-undefined command.

Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c	2005-11-03 17:44:15.000000000 +0000
+++ src/gdb/value.c	2005-11-03 17:48:33.000000000 +0000
@@ -727,6 +727,47 @@ show_values (char *num_exp, int from_tty
 
 static struct internalvar *internalvars;
 
+/* If the variable does not already exist create it and give it the value given.
+   If no value is given then the default is zero.  */
+static void
+init_if_undefined_command (char* args, int from_tty)
+{
+  struct internalvar* intvar;
+
+  /* Parse the expression - this is taken from set_command().  */
+  struct expression *expr = parse_expression (args);
+  register struct cleanup *old_chain =
+    make_cleanup (free_current_contents, &expr);
+
+  /* Validate the expression.
+     Was the expression an assignment?
+     Or even an expression at all?  */
+  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
+    {
+      printf_unfiltered ("usage: init-if-undefined $<var> = <expr>\n");
+      do_cleanups (old_chain);
+      return;
+    }
+
+  /* Extract the variable from the parsed expression.
+     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
+  if (expr->elts[1].opcode != OP_INTERNALVAR)
+    {
+      printf_unfiltered ("First parameter to init-if-undefined should be a GDB variable\n");
+      do_cleanups (old_chain);
+      return;
+    }
+  intvar = expr->elts[2].internalvar;
+
+  /* Only evaluate the expression if the lvalue is void.
+     This may still fail if the expresssion is invalid.  */
+  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
+    evaluate_expression (expr);
+
+  do_cleanups (old_chain);
+}
+
+
 /* Look up an internal variable with name NAME.  NAME should not
    normally include a dollar sign.
 
@@ -1639,4 +1680,9 @@ A few convenience variables are given va
   add_cmd ("values", no_class, show_values,
 	   _("Elements of value history around item number IDX (or last ten)."),
 	   &showlist);
+
+  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
+init-if-undefined <var> = <expr>\n\
+Ensure that an internal variable exists and set it to\n\
+a given value if it does not."));
 }
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo	2005-11-03 17:44:15.000000000 +0000
+++ src/gdb/doc/gdb.texinfo	2005-11-03 17:45:10.000000000 +0000
@@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
 @item show convenience
 Print a list of convenience variables used so far, and their values.
 Abbreviated @code{show conv}.
+
+@kindex init-if-undefined
+@cindex convenience variables, initializing
+@item init-if-undefined $@var{variable} = @var{expression}
+Set a convenience variable if it has not already been set.  This is useful
+for user-defined commands that keep some state.  It is similar, in concept,
+to using local static variables with initializers in C (except that
+convenience variables are global).  It can also be used to allow users to
+override default values used in a command script.
+
+If the variable is already defined then the expression is not evaluated so
+any side-effects do not occur.
 @end table
 
 One of the ways to use a convenience variable is as a counter to be

Re: [PATCH] init-if-undefined command

[Eli Zaretskii]

> Date: Wed, 16 Nov 2005 14:12:38 +0000
> From: Andrew STUBBS <andrew.stubbs@st.com>
> 
> The attached patch adds a new CLI command named 'init-if-undefined'.

The documentation patch is approved.  It can be committed when the
code patch is approved.  Thanks.

What do people think about mentioning new CLI commands in NEWS?  We
didn't do that until now, but if we mention command-line options, why
not mention commands?

Re: [PATCH] init-if-undefined command

[Joel Brobecker]

> What do people think about mentioning new CLI commands in NEWS?  We
> didn't do that until now, but if we mention command-line options,
> why not mention commands?

FWIW, I agree with this suggestion (pretty strongly actually).

-- 
Joel

Re: [PATCH] init-if-undefined command

[Jim Blandy]

On 11/16/05, Joel Brobecker <brobecker@adacore.com> wrote:
> > What do people think about mentioning new CLI commands in NEWS?  We
> > didn't do that until now, but if we mention command-line options,
> > why not mention commands?
>
> FWIW, I agree with this suggestion (pretty strongly actually).

If you knew everything about the previous release, you're supposed to
be able to know everything about the new release just by reading NEWS.
 You're not even supposed to have to read the manual.  Or at least
those were Stallman's rules for Emacs NEWS.  I thought it was kind of
a waste; why not just summarize changes in NEWS and point people to
the manual for details?

But yes, of course new commands should be mentioned.

Re: [PATCH] init-if-undefined command

[Joel Brobecker]

[re-adding gdb-patches, as it looks like it was removed by accident]

On Wed, Nov 16, 2005 at 04:02:15PM -0800, Jim Blandy wrote:
> On 11/16/05, Joel Brobecker <brobecker@adacore.com> wrote:
> > > If you knew everything about the previous release, you're supposed to
> > > be able to know everything about the new release just by reading NEWS.
> > >  You're not even supposed to have to read the manual.  Or at least
> > > those were Stallman's rules for Emacs NEWS.  I thought it was kind of
> > > a waste; why not point people to the manual?
> >
> > With the manual, it's not obvious what has been introduced in a release.
> > New commands, in my opinion, deserve a bit of publicity from the NEWS
> > files. The NEWS file, however, doesn't replace the manual, it's just
> > a note to inform readers that a cool new command has been introduced
> > and whose description is available in the manual.
> 
> What I meant was, Stallman wanted each new feature fully documented in
> NEWS; I felt it should be sufficient to summarize the new feature in
> NEWS, and refer the user to the manual for the details.

I agree.

-- 
Joel

Re: [PATCH] init-if-undefined command

[Daniel Jacobowitz]

On Wed, Nov 16, 2005 at 09:36:52PM +0200, Eli Zaretskii wrote:
> What do people think about mentioning new CLI commands in NEWS?  We
> didn't do that until now, but if we mention command-line options, why
> not mention commands?

I agree.

-- 
Daniel Jacobowitz
CodeSourcery, LLC

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

Andrew Stubbs wrote:
> The attached patch adds a new CLI command named 'init-if-undefined'.
> 
> This is essentially the same a 'set variable' (for convenience variables 
> only), but does not set the variable if it already has a value.
> 
> It is useful in scripts whose values can be overridden, or as an 
> approximation of a statically initialised variable.

Here's another one that ought to be easy to approve/reject.

The docs have been approved and we have decided that this should be 
mentioned in the NEWS if/when it goes in, but nobody has said anything 
about the code.

I don't think this one should be too much trouble because it does not 
change existing behaviour or do much out of keeping with other commands.

Is it OK?

Thanks

Andrew Stubbs

Re: [PATCH] init-if-undefined command

[Jim Blandy]

On 11/16/05, Andrew STUBBS <andrew.stubbs@st.com> wrote:
> +      printf_unfiltered ("usage: init-if-undefined $<var> = <expr>\n");

Provide a full English sentence here, not a traditional Unix "usage:" thingy.

> +      printf_unfiltered ("First parameter to init-if-undefined should be a GDB variable\n");

This should be a full sentence, with a preceding "The" and a period.

> +  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
> +init-if-undefined <var> = <expr>\n\
> +Ensure that an internal variable exists and set it to\n\
> +a given value if it does not."));

Use upper case for syntactic metavariables, like VAR and EXPR, not
<angle brackets>.  Refer to the metavariables in the doc string:
"Ensure that VAR ... and set it to the value of EXPR", etc.

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

[-- Attachment #1: Type: text/plain, Size: 282 bytes --]

Here is another version with the various help strings updated.

I have rewritten the main help because I noticed it did not start with 
something suitable for 'help data'. I also added a little more 
information about its exact behaviour.

I hope this is better now.

Andrew Stubbs

[-- Attachment #2: init-if-undefined.patch --]
[-- Type: text/plain, Size: 3736 bytes --]

2005-11-30  Andrew Stubbs  <andrew.stubbs@st.com>

	* value.c (init_if_undefined_command): New function.
	(_initialize_values): Add command init-if-undefined.

doc/
	* gdb.texinfo (Convenience variables): Add init-if-undefined command.

Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c	2005-11-29 16:35:46.000000000 +0000
+++ src/gdb/value.c	2005-11-30 12:46:34.000000000 +0000
@@ -727,6 +727,47 @@ show_values (char *num_exp, int from_tty
 
 static struct internalvar *internalvars;
 
+/* If the variable does not already exist create it and give it the value given.
+   If no value is given then the default is zero.  */
+static void
+init_if_undefined_command (char* args, int from_tty)
+{
+  struct internalvar* intvar;
+
+  /* Parse the expression - this is taken from set_command().  */
+  struct expression *expr = parse_expression (args);
+  register struct cleanup *old_chain =
+    make_cleanup (free_current_contents, &expr);
+
+  /* Validate the expression.
+     Was the expression an assignment?
+     Or even an expression at all?  */
+  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
+    {
+      printf_unfiltered ("Init-if-undefined requires an assignment expression.\n");
+      do_cleanups (old_chain);
+      return;
+    }
+
+  /* Extract the variable from the parsed expression.
+     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
+  if (expr->elts[1].opcode != OP_INTERNALVAR)
+    {
+      printf_unfiltered ("The first parameter to init-if-undefined should be a GDB variable\n");
+      do_cleanups (old_chain);
+      return;
+    }
+  intvar = expr->elts[2].internalvar;
+
+  /* Only evaluate the expression if the lvalue is void.
+     This may still fail if the expresssion is invalid.  */
+  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
+    evaluate_expression (expr);
+
+  do_cleanups (old_chain);
+}
+
+
 /* Look up an internal variable with name NAME.  NAME should not
    normally include a dollar sign.
 
@@ -1639,4 +1680,11 @@ A few convenience variables are given va
   add_cmd ("values", no_class, show_values,
 	   _("Elements of value history around item number IDX (or last ten)."),
 	   &showlist);
+
+  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
+Initialize a convenience variable if necessary.\n\
+init-if-undefined VARIABLE = EXPRESSION\n\
+Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
+exist or does not contain a value.  The EXPRESSION is not evaluated if the\n\
+VARIABLE is already initialized."));
 }
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo	2005-11-29 16:36:23.000000000 +0000
+++ src/gdb/doc/gdb.texinfo	2005-11-30 12:24:23.000000000 +0000
@@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
 @item show convenience
 Print a list of convenience variables used so far, and their values.
 Abbreviated @code{show conv}.
+
+@kindex init-if-undefined
+@cindex convenience variables, initializing
+@item init-if-undefined $@var{variable} = @var{expression}
+Set a convenience variable if it has not already been set.  This is useful
+for user-defined commands that keep some state.  It is similar, in concept,
+to using local static variables with initializers in C (except that
+convenience variables are global).  It can also be used to allow users to
+override default values used in a command script.
+
+If the variable is already defined then the expression is not evaluated so
+any side-effects do not occur.
 @end table
 
 One of the ways to use a convenience variable is as a counter to be

Re: [PATCH] init-if-undefined command

[Jim Blandy]

Okay, that looks better.  We agreed we need a NEWS entry, too; could
you include that in your patch?  Once Eli approves the NEWS entry,
this can go in.

On 11/30/05, Andrew STUBBS <andrew.stubbs@st.com> wrote:
> Here is another version with the various help strings updated.
>
> I have rewritten the main help because I noticed it did not start with
> something suitable for 'help data'. I also added a little more
> information about its exact behaviour.
>
> I hope this is better now.
>
> Andrew Stubbs
>
>
> 2005-11-30  Andrew Stubbs  <andrew.stubbs@st.com>
>
>         * value.c (init_if_undefined_command): New function.
>         (_initialize_values): Add command init-if-undefined.
>
> doc/
>         * gdb.texinfo (Convenience variables): Add init-if-undefined command.
>
> Index: src/gdb/value.c
> ===================================================================
> --- src.orig/gdb/value.c        2005-11-29 16:35:46.000000000 +0000
> +++ src/gdb/value.c     2005-11-30 12:46:34.000000000 +0000
> @@ -727,6 +727,47 @@ show_values (char *num_exp, int from_tty
>
>  static struct internalvar *internalvars;
>
> +/* If the variable does not already exist create it and give it the value given.
> +   If no value is given then the default is zero.  */
> +static void
> +init_if_undefined_command (char* args, int from_tty)
> +{
> +  struct internalvar* intvar;
> +
> +  /* Parse the expression - this is taken from set_command().  */
> +  struct expression *expr = parse_expression (args);
> +  register struct cleanup *old_chain =
> +    make_cleanup (free_current_contents, &expr);
> +
> +  /* Validate the expression.
> +     Was the expression an assignment?
> +     Or even an expression at all?  */
> +  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
> +    {
> +      printf_unfiltered ("Init-if-undefined requires an assignment expression.\n");
> +      do_cleanups (old_chain);
> +      return;
> +    }
> +
> +  /* Extract the variable from the parsed expression.
> +     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
> +  if (expr->elts[1].opcode != OP_INTERNALVAR)
> +    {
> +      printf_unfiltered ("The first parameter to init-if-undefined should be a GDB variable\n");
> +      do_cleanups (old_chain);
> +      return;
> +    }
> +  intvar = expr->elts[2].internalvar;
> +
> +  /* Only evaluate the expression if the lvalue is void.
> +     This may still fail if the expresssion is invalid.  */
> +  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
> +    evaluate_expression (expr);
> +
> +  do_cleanups (old_chain);
> +}
> +
> +
>  /* Look up an internal variable with name NAME.  NAME should not
>     normally include a dollar sign.
>
> @@ -1639,4 +1680,11 @@ A few convenience variables are given va
>    add_cmd ("values", no_class, show_values,
>            _("Elements of value history around item number IDX (or last ten)."),
>            &showlist);
> +
> +  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
> +Initialize a convenience variable if necessary.\n\
> +init-if-undefined VARIABLE = EXPRESSION\n\
> +Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
> +exist or does not contain a value.  The EXPRESSION is not evaluated if the\n\
> +VARIABLE is already initialized."));
>  }
> Index: src/gdb/doc/gdb.texinfo
> ===================================================================
> --- src.orig/gdb/doc/gdb.texinfo        2005-11-29 16:36:23.000000000 +0000
> +++ src/gdb/doc/gdb.texinfo     2005-11-30 12:24:23.000000000 +0000
> @@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
>  @item show convenience
>  Print a list of convenience variables used so far, and their values.
>  Abbreviated @code{show conv}.
> +
> +@kindex init-if-undefined
> +@cindex convenience variables, initializing
> +@item init-if-undefined $@var{variable} = @var{expression}
> +Set a convenience variable if it has not already been set.  This is useful
> +for user-defined commands that keep some state.  It is similar, in concept,
> +to using local static variables with initializers in C (except that
> +convenience variables are global).  It can also be used to allow users to
> +override default values used in a command script.
> +
> +If the variable is already defined then the expression is not evaluated so
> +any side-effects do not occur.
>  @end table
>
>  One of the ways to use a convenience variable is as a counter to be
>
>
>

Re: [PATCH] init-if-undefined command

[Daniel Jacobowitz]

On Wed, Nov 30, 2005 at 02:12:33PM +0000, Andrew STUBBS wrote:
> +      printf_unfiltered ("Init-if-undefined requires an assignment expression.\n");

Is there any reason this, and the other outputs, should not be
_("gettextized")?

Also, should this be an error()?

> +  /* Extract the variable from the parsed expression.
> +     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
> +  if (expr->elts[1].opcode != OP_INTERNALVAR)
> +    {
> +      printf_unfiltered ("The first parameter to init-if-undefined should be a GDB variable\n");
> +      do_cleanups (old_chain);
> +      return;
> +    }

Ditto.


-- 
Daniel Jacobowitz
CodeSourcery, LLC

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

[-- Attachment #1: Type: text/plain, Size: 563 bytes --]

Jim Blandy wrote:
> On 11/30/05, Daniel Jacobowitz <drow@false.org> wrote:
> 
>>On Wed, Nov 30, 2005 at 02:12:33PM +0000, Andrew STUBBS wrote:
>>
>>>+      printf_unfiltered ("Init-if-undefined requires an assignment expression.\n");
>>
>>Is there any reason this, and the other outputs, should not be
>>_("gettextized")?
>>
>>Also, should this be an error()?
> 
> These are things I should have noticed.  They need to be fixed before
> this can be committed.

Absolutely, the only reason for this is incompetence. How about the 
attached?

Thanks

Andrew Stubbs

[-- Attachment #2: init-if-undefined.patch --]
[-- Type: text/plain, Size: 3589 bytes --]

2005-12-01  Andrew Stubbs  <andrew.stubbs@st.com>

	* value.c (init_if_undefined_command): New function.
	(_initialize_values): Add command init-if-undefined.

doc/
	* gdb.texinfo (Convenience variables): Add init-if-undefined command.

Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c	2005-11-29 16:35:46.000000000 +0000
+++ src/gdb/value.c	2005-12-01 11:43:06.000000000 +0000
@@ -727,6 +727,39 @@ show_values (char *num_exp, int from_tty
 
 static struct internalvar *internalvars;
 
+/* If the variable does not already exist create it and give it the value given.
+   If no value is given then the default is zero.  */
+static void
+init_if_undefined_command (char* args, int from_tty)
+{
+  struct internalvar* intvar;
+
+  /* Parse the expression - this is taken from set_command().  */
+  struct expression *expr = parse_expression (args);
+  register struct cleanup *old_chain =
+    make_cleanup (free_current_contents, &expr);
+
+  /* Validate the expression.
+     Was the expression an assignment?
+     Or even an expression at all?  */
+  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
+    error (_("Init-if-undefined requires an assignment expression."));
+
+  /* Extract the variable from the parsed expression.
+     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
+  if (expr->elts[1].opcode != OP_INTERNALVAR)
+    error (_("The first parameter to init-if-undefined should be a GDB variable."));
+  intvar = expr->elts[2].internalvar;
+
+  /* Only evaluate the expression if the lvalue is void.
+     This may still fail if the expresssion is invalid.  */
+  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
+    evaluate_expression (expr);
+
+  do_cleanups (old_chain);
+}
+
+
 /* Look up an internal variable with name NAME.  NAME should not
    normally include a dollar sign.
 
@@ -1639,4 +1672,11 @@ A few convenience variables are given va
   add_cmd ("values", no_class, show_values,
 	   _("Elements of value history around item number IDX (or last ten)."),
 	   &showlist);
+
+  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
+Initialize a convenience variable if necessary.\n\
+init-if-undefined VARIABLE = EXPRESSION\n\
+Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
+exist or does not contain a value.  The EXPRESSION is not evaluated if the\n\
+VARIABLE is already initialized."));
 }
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo	2005-11-29 16:36:23.000000000 +0000
+++ src/gdb/doc/gdb.texinfo	2005-12-01 11:36:10.000000000 +0000
@@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
 @item show convenience
 Print a list of convenience variables used so far, and their values.
 Abbreviated @code{show conv}.
+
+@kindex init-if-undefined
+@cindex convenience variables, initializing
+@item init-if-undefined $@var{variable} = @var{expression}
+Set a convenience variable if it has not already been set.  This is useful
+for user-defined commands that keep some state.  It is similar, in concept,
+to using local static variables with initializers in C (except that
+convenience variables are global).  It can also be used to allow users to
+override default values used in a command script.
+
+If the variable is already defined then the expression is not evaluated so
+any side-effects do not occur.
 @end table
 
 One of the ways to use a convenience variable is as a counter to be

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

Here's the NEWS to go with my patch.

2005-12-01  Andrew Stubbs  <andrew.stubbs@st.com>

         * NEWS (Changes since GDB 6.3): Rename to 'Changes in GDB 6.4'.
         (Changes since GDB 6.4): New section.
         Mention new command init-if-undefined.

--- src.orig/gdb/NEWS   2005-12-01 17:27:11.000000000 +0000
+++ src/gdb/NEWS        2005-12-01 17:28:05.000000000 +0000
@@ -1,7 +1,13 @@
                 What has changed in GDB?
              (Organized release by release)

-*** Changes since GDB 6.3
+*** Changes since GDB 6.4
+
+* New commands
+
+init-if-undefined              Initialize a convenience variable if 
necessary.
+
+*** Changes in GDB 6.4

  * New native configurations

Re: [PATCH] init-if-undefined command

[Jim Blandy]

On 12/1/05, Andrew STUBBS <andrew.stubbs@st.com> wrote:
> --- src.orig/gdb/NEWS   2005-12-01 17:27:11.000000000 +0000
> +++ src/gdb/NEWS        2005-12-01 17:28:05.000000000 +0000
> @@ -1,7 +1,13 @@
>                  What has changed in GDB?
>               (Organized release by release)
>
> -*** Changes since GDB 6.3
> +*** Changes since GDB 6.4
> +
> +* New commands
> +
> +init-if-undefined              Initialize a convenience variable if
> necessary.
> +
> +*** Changes in GDB 6.4
>
>   * New native configurations

Shouldn't that latter inserted heading be "6.3"?

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

Jim Blandy wrote:
> On 12/1/05, Andrew STUBBS <andrew.stubbs@st.com> wrote:
> 
>>--- src.orig/gdb/NEWS   2005-12-01 17:27:11.000000000 +0000
>>+++ src/gdb/NEWS        2005-12-01 17:28:05.000000000 +0000
>>@@ -1,7 +1,13 @@
>>                 What has changed in GDB?
>>              (Organized release by release)
>>
>>-*** Changes since GDB 6.3
>>+*** Changes since GDB 6.4
>>+
>>+* New commands
>>+
>>+init-if-undefined              Initialize a convenience variable if
>>necessary.
>>+
>>+*** Changes in GDB 6.4
>>
>>  * New native configurations
> 
> 
> Shouldn't that latter inserted heading be "6.3"?
> 

No. The changes 'since 6.3' are 'in 6.4'. A similar change is already on 
the 6.4 branch.

Re: [PATCH] init-if-undefined command

[Eli Zaretskii]

> Date: Thu, 01 Dec 2005 17:30:15 +0000
> From: Andrew STUBBS <andrew.stubbs@st.com>
> Cc: Jim Blandy <jimb@red-bean.com>, gdb-patches@sources.redhat.com
> 
> Here's the NEWS to go with my patch.

Thanks.

> +init-if-undefined              Initialize a convenience variable if 
> necessary.

Your mailer seems to be wrapping lines.

Anyway, I'd suggest a slightly different text:

  init-if-undefined           Initialize a convenience variable, but
  			      only if it doesn't already have a value.

(This is more clear than the vague ``if necessary'', IMHO.)

WDYT?

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

Eli Zaretskii wrote:
> Your mailer seems to be wrapping lines.

Normally I attach them to avoid wrapping, but this time I cut-n-paste it 
into the body because I didn't want to post all the code again.

> Anyway, I'd suggest a slightly different text:
> 
>   init-if-undefined           Initialize a convenience variable, but
>   			      only if it doesn't already have a value.
> 
> (This is more clear than the vague ``if necessary'', IMHO.)
> 
> WDYT?
> 

That's fine by me. I'll put it in as you say.

Thanks

Andrew

Re: [PATCH] init-if-undefined command

[Jim Blandy]

This looks okay.

On 12/1/05, Andrew STUBBS <andrew.stubbs@st.com> wrote:
> Jim Blandy wrote:
> > On 11/30/05, Daniel Jacobowitz <drow@false.org> wrote:
> >
> >>On Wed, Nov 30, 2005 at 02:12:33PM +0000, Andrew STUBBS wrote:
> >>
> >>>+      printf_unfiltered ("Init-if-undefined requires an assignment expression.\n");
> >>
> >>Is there any reason this, and the other outputs, should not be
> >>_("gettextized")?
> >>
> >>Also, should this be an error()?
> >
> > These are things I should have noticed.  They need to be fixed before
> > this can be committed.
>
> Absolutely, the only reason for this is incompetence. How about the
> attached?
>
> Thanks
>
> Andrew Stubbs
>
>
> 2005-12-01  Andrew Stubbs  <andrew.stubbs@st.com>
>
>         * value.c (init_if_undefined_command): New function.
>         (_initialize_values): Add command init-if-undefined.
>
> doc/
>         * gdb.texinfo (Convenience variables): Add init-if-undefined command.
>
> Index: src/gdb/value.c
> ===================================================================
> --- src.orig/gdb/value.c        2005-11-29 16:35:46.000000000 +0000
> +++ src/gdb/value.c     2005-12-01 11:43:06.000000000 +0000
> @@ -727,6 +727,39 @@ show_values (char *num_exp, int from_tty
>
>  static struct internalvar *internalvars;
>
> +/* If the variable does not already exist create it and give it the value given.
> +   If no value is given then the default is zero.  */
> +static void
> +init_if_undefined_command (char* args, int from_tty)
> +{
> +  struct internalvar* intvar;
> +
> +  /* Parse the expression - this is taken from set_command().  */
> +  struct expression *expr = parse_expression (args);
> +  register struct cleanup *old_chain =
> +    make_cleanup (free_current_contents, &expr);
> +
> +  /* Validate the expression.
> +     Was the expression an assignment?
> +     Or even an expression at all?  */
> +  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
> +    error (_("Init-if-undefined requires an assignment expression."));
> +
> +  /* Extract the variable from the parsed expression.
> +     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
> +  if (expr->elts[1].opcode != OP_INTERNALVAR)
> +    error (_("The first parameter to init-if-undefined should be a GDB variable."));
> +  intvar = expr->elts[2].internalvar;
> +
> +  /* Only evaluate the expression if the lvalue is void.
> +     This may still fail if the expresssion is invalid.  */
> +  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
> +    evaluate_expression (expr);
> +
> +  do_cleanups (old_chain);
> +}
> +
> +
>  /* Look up an internal variable with name NAME.  NAME should not
>     normally include a dollar sign.
>
> @@ -1639,4 +1672,11 @@ A few convenience variables are given va
>    add_cmd ("values", no_class, show_values,
>            _("Elements of value history around item number IDX (or last ten)."),
>            &showlist);
> +
> +  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
> +Initialize a convenience variable if necessary.\n\
> +init-if-undefined VARIABLE = EXPRESSION\n\
> +Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
> +exist or does not contain a value.  The EXPRESSION is not evaluated if the\n\
> +VARIABLE is already initialized."));
>  }
> Index: src/gdb/doc/gdb.texinfo
> ===================================================================
> --- src.orig/gdb/doc/gdb.texinfo        2005-11-29 16:36:23.000000000 +0000
> +++ src/gdb/doc/gdb.texinfo     2005-12-01 11:36:10.000000000 +0000
> @@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
>  @item show convenience
>  Print a list of convenience variables used so far, and their values.
>  Abbreviated @code{show conv}.
> +
> +@kindex init-if-undefined
> +@cindex convenience variables, initializing
> +@item init-if-undefined $@var{variable} = @var{expression}
> +Set a convenience variable if it has not already been set.  This is useful
> +for user-defined commands that keep some state.  It is similar, in concept,
> +to using local static variables with initializers in C (except that
> +convenience variables are global).  It can also be used to allow users to
> +override default values used in a command script.
> +
> +If the variable is already defined then the expression is not evaluated so
> +any side-effects do not occur.
>  @end table
>
>  One of the ways to use a convenience variable is as a counter to be
>
>
>

Re: [PATCH] init-if-undefined command

[Andrew STUBBS]

[-- Attachment #1: Type: text/plain, Size: 150 bytes --]

Jim Blandy wrote:
> This looks okay.

Thanks.

I have committed the attached. This includes the NEWS incorporating 
Eli's suggestions.

Andrew Stubbs

[-- Attachment #2: init-if-undefined.patch --]
[-- Type: text/plain, Size: 4255 bytes --]

2005-12-02  Andrew Stubbs  <andrew.stubbs@st.com>

	* value.c (init_if_undefined_command): New function.
	(_initialize_values): Add command init-if-undefined.
	* NEWS (Changes since GDB 6.3): Rename to 'Changes in GDB 6.4'.
	(Changes since GDB 6.4): New section.
	Mention new command init-if-undefined.

doc/
	* gdb.texinfo (Convenience variables): Add init-if-undefined command.

Index: src/gdb/value.c
===================================================================
--- src.orig/gdb/value.c	2005-12-02 10:54:11.000000000 +0000
+++ src/gdb/value.c	2005-12-02 11:29:50.000000000 +0000
@@ -727,6 +727,39 @@ show_values (char *num_exp, int from_tty
 
 static struct internalvar *internalvars;
 
+/* If the variable does not already exist create it and give it the value given.
+   If no value is given then the default is zero.  */
+static void
+init_if_undefined_command (char* args, int from_tty)
+{
+  struct internalvar* intvar;
+
+  /* Parse the expression - this is taken from set_command().  */
+  struct expression *expr = parse_expression (args);
+  register struct cleanup *old_chain =
+    make_cleanup (free_current_contents, &expr);
+
+  /* Validate the expression.
+     Was the expression an assignment?
+     Or even an expression at all?  */
+  if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
+    error (_("Init-if-undefined requires an assignment expression."));
+
+  /* Extract the variable from the parsed expression.
+     In the case of an assign the lvalue will be in elts[1] and elts[2].  */
+  if (expr->elts[1].opcode != OP_INTERNALVAR)
+    error (_("The first parameter to init-if-undefined should be a GDB variable."));
+  intvar = expr->elts[2].internalvar;
+
+  /* Only evaluate the expression if the lvalue is void.
+     This may still fail if the expresssion is invalid.  */
+  if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
+    evaluate_expression (expr);
+
+  do_cleanups (old_chain);
+}
+
+
 /* Look up an internal variable with name NAME.  NAME should not
    normally include a dollar sign.
 
@@ -1639,4 +1672,11 @@ A few convenience variables are given va
   add_cmd ("values", no_class, show_values,
 	   _("Elements of value history around item number IDX (or last ten)."),
 	   &showlist);
+
+  add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
+Initialize a convenience variable if necessary.\n\
+init-if-undefined VARIABLE = EXPRESSION\n\
+Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
+exist or does not contain a value.  The EXPRESSION is not evaluated if the\n\
+VARIABLE is already initialized."));
 }
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo	2005-12-02 11:29:50.000000000 +0000
+++ src/gdb/doc/gdb.texinfo	2005-12-02 11:29:50.000000000 +0000
@@ -6131,6 +6131,18 @@ variable, when used as an expression, ha
 @item show convenience
 Print a list of convenience variables used so far, and their values.
 Abbreviated @code{show conv}.
+
+@kindex init-if-undefined
+@cindex convenience variables, initializing
+@item init-if-undefined $@var{variable} = @var{expression}
+Set a convenience variable if it has not already been set.  This is useful
+for user-defined commands that keep some state.  It is similar, in concept,
+to using local static variables with initializers in C (except that
+convenience variables are global).  It can also be used to allow users to
+override default values used in a command script.
+
+If the variable is already defined then the expression is not evaluated so
+any side-effects do not occur.
 @end table
 
 One of the ways to use a convenience variable is as a counter to be
Index: src/gdb/NEWS
===================================================================
--- src.orig/gdb/NEWS	2005-12-02 10:54:11.000000000 +0000
+++ src/gdb/NEWS	2005-12-02 11:33:01.000000000 +0000
@@ -1,7 +1,14 @@
 		What has changed in GDB?
 	     (Organized release by release)
 
-*** Changes since GDB 6.3
+*** Changes since GDB 6.4
+
+* New commands
+
+init-if-undefined		Initialize a convenience variable, but
+				only if it doesn't already have a value.
+
+*** Changes in GDB 6.4
 
 * New native configurations