[patch] Add support for hooking prefix commands

[patch] Add support for hooking prefix commands

[Sorin Otescu]

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Hi all,

I recently needed to add a hook for the "info threads" command. 
Unfortunately, this was not possible because GDB only allows hooking of 
single word commands.
This patch adds support for multi-word command (prefix command) hooks. 
In my case, the format of the hook commands is:

define hook-info_threads
define hookpost-info_threads

Sorin

gdb/cli/
2011-03-09  Sorin Otescu<sorinu@gmail.com>

	* cli-script.c (define_command): Add support for hooking prefix commands.
         Example usage: for hooking "info threads", a hook command will be defined as:
         define hook-info_threads and/or define hookpost-info_threads





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--- cli-script.c.orig	2010-05-17 22:28:12.000000000 +0300
+++ cli-script.c	2011-03-09 11:37:04.917093842 +0200
@@ -1416,8 +1350,9 @@
       CMD_POST_HOOK
     };
   struct command_line *cmds;
-  struct cmd_list_element *c, *newc, *hookc = 0, **list;
-  char *tem, *comfull;
+  struct cmd_list_element *c, *newc, *hookc = 0, **list;
+  char *tem, *tem2, *comfull;
+  char tembuf[MAX_TMPBUF];
   char tmpbuf[MAX_TMPBUF];
   int  hook_type      = CMD_NO_HOOK;
   int  hook_name_size = 0;
--- cli-script.c.orig	2010-05-17 22:28:12.000000000 +0300
+++ cli-script.c	2011-03-09 11:37:04.917093842 +0200
@@ -1430,8 +1365,11 @@
   comfull = comname;
   list = validate_comname (&comname);
 
+  strncpy(tembuf, comname, MAX_TMPBUF);
+  tembuf[MAX_TMPBUF-1] = 0;
+
   /* Look it up, and verify that we got an exact match.  */
-  tem = comname;
+  tem = tembuf;
   c = lookup_cmd (&tem, *list, "", -1, 1);
   if (c && strcmp (comname, c->name) != 0)
     c = 0;
--- cli-script.c.orig	2010-05-17 22:28:12.000000000 +0300
+++ cli-script.c	2011-03-09 11:37:04.917093842 +0200
@@ -1465,11 +1402,26 @@
    
   if (hook_type != CMD_NO_HOOK)
     {
+      /* Convert _ characters into spaces, to allow hooking prefix commands */
+      tem = tembuf + hook_name_size;
+      tem2 = strchr(tem, '_');
+      while (tem2)
+        {
+          *tem2 = ' ';
+          tem2 = strchr(tem2+1, '_');
+        }
+
       /* Look up cmd it hooks, and verify that we got an exact match.  */
-      tem = comname + hook_name_size;
       hookc = lookup_cmd (&tem, *list, "", -1, 0);
-      if (hookc && strcmp (comname + hook_name_size, hookc->name) != 0)
+      while (hookc && *tem)
+        {
+          /* tem might point to the argument of a prefix command */
+          if (hookc->prefixlist)
+              hookc = lookup_cmd (&tem, *hookc->prefixlist, "", -1, 0);
+          else
 	hookc = 0;
+        }
+
       if (!hookc)
 	{
 	  warning (_("Your new `%s' command does not hook any existing command."),

Re: [patch] Add support for hooking prefix commands

[Eli Zaretskii]

> Date: Wed, 09 Mar 2011 13:15:15 +0200
> From: Sorin Otescu <sorinu@gmail.com>
> 
> I recently needed to add a hook for the "info threads" command. 
> Unfortunately, this was not possible because GDB only allows hooking of 
> single word commands.
> This patch adds support for multi-word command (prefix command) hooks. 
> In my case, the format of the hook commands is:

Thanks.

> define hook-info_threads
> define hookpost-info_threads

Can we have underscore characters in commands?  If so, this
implementation would defeat hooking them.

Anyway, if this is accepted, please write a short patch for the manual
as well.

Re: [patch] Add support for hooking prefix commands

[Sorin Otescu]

On 03/09/2011 02:40 PM, Eli Zaretskii wrote:
>> Date: Wed, 09 Mar 2011 13:15:15 +0200
>> From: Sorin Otescu<sorinu@gmail.com>
>>
>> I recently needed to add a hook for the "info threads" command.
>> Unfortunately, this was not possible because GDB only allows hooking of
>> single word commands.
>> This patch adds support for multi-word command (prefix command) hooks.
>> In my case, the format of the hook commands is:
> Thanks.
>
>> define hook-info_threads
>> define hookpost-info_threads
> Can we have underscore characters in commands?  If so, this
> implementation would defeat hooking them.
>
It is possible to define commands containing underscores, but none of 
the built-in commands
contain any (they all use dash).
> Anyway, if this is accepted, please write a short patch for the manual
> as well.
>
The documentation for 7.2 suggests this functionality is already there; 
the difference is that
you need to hook the last word of the command (in this case, 
hook-threads). I wonder if
that's enough / better... This patch was generated from 7.0 and adapted 
to 7.2.

Re: [patch] Add support for hooking prefix commands

[Eli Zaretskii]

> Date: Wed, 09 Mar 2011 14:54:44 +0200
> From: Sorin Otescu <sorinu@gmail.com>
> CC: gdb-patches@sourceware.org
> 
> > Can we have underscore characters in commands?  If so, this
> > implementation would defeat hooking them.
> >
> It is possible to define commands containing underscores, but none of 
> the built-in commands
> contain any (they all use dash).

That could be a problem.  What do others think?

> > Anyway, if this is accepted, please write a short patch for the manual
> > as well.
> >
> The documentation for 7.2 suggests this functionality is already there; 
> the difference is that
> you need to hook the last word of the command (in this case, 
> hook-threads). I wonder if
> that's enough / better... This patch was generated from 7.0 and adapted 
> to 7.2.

Are you saying that 7.2 already supports this feature?  Or are you
saying that it's documented there, but doesn't work?

Re: [patch] Add support for hooking prefix commands

[Sorin Otescu]

On 03/09/2011 03:39 PM, Eli Zaretskii wrote:
>> Date: Wed, 09 Mar 2011 14:54:44 +0200
>> From: Sorin Otescu<sorinu@gmail.com>
>> CC: gdb-patches@sourceware.org
>>
>>> Can we have underscore characters in commands?  If so, this
>>> implementation would defeat hooking them.
>>>
>> It is possible to define commands containing underscores, but none of
>> the built-in commands
>> contain any (they all use dash).
> That could be a problem.  What do others think?
>
>>> Anyway, if this is accepted, please write a short patch for the manual
>>> as well.
>>>
>> The documentation for 7.2 suggests this functionality is already there;
>> the difference is that
>> you need to hook the last word of the command (in this case,
>> hook-threads). I wonder if
>> that's enough / better... This patch was generated from 7.0 and adapted
>> to 7.2.
> Are you saying that 7.2 already supports this feature?  Or are you
> saying that it's documented there, but doesn't work?
>
It's documented there, but I can't test it ATM, because I'm using a gdb 
from a toolchain and it's not
easy for me to switch to 7.2. Maybe somebody can shed a light on the issue.
I see some problems with that approach, even if it works. What happens 
if two or more commands
have the same second word ?  Which one would be used ?

Re: [patch] Add support for hooking prefix commands

[Eli Zaretskii]

> Date: Wed, 09 Mar 2011 15:54:41 +0200
> From: Sorin Otescu <sorinu@gmail.com>
> 
> I see some problems with that approach, even if it works. What happens 
> if two or more commands
> have the same second word ?  Which one would be used ?

I see no problem.  For hooking "target remote" you'd say

  define target hook-remote

and for hooking "foo remote" you'd say

  define foo hook-remote

This is what the manual says.

Re: [patch] Add support for hooking prefix commands

[Eli Zaretskii]

> Date: Wed, 09 Mar 2011 15:54:41 +0200
> From: Sorin Otescu <sorinu@gmail.com>
> 
> > Are you saying that 7.2 already supports this feature?  Or are you
> > saying that it's documented there, but doesn't work?
> >
> It's documented there, but I can't test it ATM, because I'm using a gdb 
> from a toolchain and it's not
> easy for me to switch to 7.2. Maybe somebody can shed a light on the issue.

I just tried this (with "info breakpoints") in GDB 7.2, and it worked
for me.

So I think you should upgrade when you can, and then you will have
this feature.

Re: [patch] Add support for hooking prefix commands

[Sorin Otescu]

On 03/09/2011 04:03 PM, Eli Zaretskii wrote:
>> Date: Wed, 09 Mar 2011 15:54:41 +0200
>> From: Sorin Otescu<sorinu@gmail.com>
>>
>>> Are you saying that 7.2 already supports this feature?  Or are you
>>> saying that it's documented there, but doesn't work?
>>>
>> It's documented there, but I can't test it ATM, because I'm using a gdb
>> from a toolchain and it's not
>> easy for me to switch to 7.2. Maybe somebody can shed a light on the issue.
> I just tried this (with "info breakpoints") in GDB 7.2, and it worked
> for me.
>
> So I think you should upgrade when you can, and then you will have
> this feature.
>
Thanks ! That's what you get for using obsolete software and not RTFM :)