Don't prune program spaces when doing "maintenance info program-spaces"

  While debugging a program spaces issue, I found that "maintenance info
program-spaces" pruned the program spaces prior to printing them. I
don't think a command to inspect the state of the program (especially
a maintenance one) should modify the state. All it can do is potentially
hide bugs.

gdb/Changelog:

	* progspace.c (print_program_space): Add "prune" parameter.
	(maintenance_info_program_spaces_command): Update call to
	print_program_space with new parameter.
---
 gdb/progspace.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)
  

On Wednesday, September 24 2014, Simon Marchi wrote:

> While debugging a program spaces issue, I found that "maintenance info
> program-spaces" pruned the program spaces prior to printing them. I
> don't think a command to inspect the state of the program (especially
> a maintenance one) should modify the state. All it can do is potentially
> hide bugs.

Hi Simon,

Thanks for the patch.  I agree with your rationale, and just have one
comment.

> ---
>  gdb/progspace.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/gdb/progspace.c b/gdb/progspace.c
> index a74b6ab..aef2d4e 100644
> --- a/gdb/progspace.c
> +++ b/gdb/progspace.c
> @@ -272,18 +272,19 @@ prune_program_spaces (void)
>  
>  /* Prints the list of program spaces and their details on UIOUT.  If
>     REQUESTED is not -1, it's the ID of the pspace that should be
> -   printed.  Otherwise, all spaces are printed.  */
> +   printed.  Otherwise, all spaces are printed.  If PRUNE is true,
> +   prune the unused program spaces prior to printing them, so they
> +   won't be displayed. */
>  
>  static void
> -print_program_space (struct ui_out *uiout, int requested)
> +print_program_space (struct ui_out *uiout, int requested, int prune)
>  {
>    struct program_space *pspace;
>    int count = 0;
>    struct cleanup *old_chain;
>  
> -  /* Might as well prune away unneeded ones, so the user doesn't even
> -     seem them.  */
> -  prune_program_spaces ();
> +  if (prune)
> +    prune_program_spaces ();
>  
>    /* Compute number of pspaces we will print.  */
>    ALL_PSPACES (pspace)
> @@ -385,7 +386,7 @@ maintenance_info_program_spaces_command (char *args, int from_tty)
>  	error (_("program space ID %d not known."), requested);
>      }
>  
> -  print_program_space (current_uiout, requested);
> +  print_program_space (current_uiout, requested, 0 /* prune */);

Just like we had a comment explaining why we were pruning progspaces, I
think a small comment here explaining why we are *not* pruning them
would be neat.

Otherwise, looks good to me (this is not an approval).

Thanks,
  

On 2014-09-24 02:53 PM, Sergio Durigan Junior wrote:
>> @@ -385,7 +386,7 @@ maintenance_info_program_spaces_command (char *args, int from_tty)
>>  	error (_("program space ID %d not known."), requested);
>>      }
>>  
>> -  print_program_space (current_uiout, requested);
>> +  print_program_space (current_uiout, requested, 0 /* prune */);
> 
> Just like we had a comment explaining why we were pruning progspaces, I
> think a small comment here explaining why we are *not* pruning them
> would be neat.

Sure, I could add to the current patch, above the call to print_program_space:

  /* Since this is an "info" command, we want to avoid modifying
     the state of the debugger. Therefore, don't prune unused
     program spaces. */
  

On Wednesday, September 24 2014, Simon Marchi wrote:

> Sure, I could add to the current patch, above the call to print_program_space:
>
>   /* Since this is an "info" command, we want to avoid modifying
>      the state of the debugger. Therefore, don't prune unused
>      program spaces. */

Nice, thanks Simon.
  

On Wed, Sep 24, 2014 at 11:11 AM, Simon Marchi
<simon.marchi@ericsson.com> wrote:
> While debugging a program spaces issue, I found that "maintenance info
> program-spaces" pruned the program spaces prior to printing them. I
> don't think a command to inspect the state of the program (especially
> a maintenance one) should modify the state. All it can do is potentially
> hide bugs.
>
> gdb/Changelog:
>
>         * progspace.c (print_program_space): Add "prune" parameter.
>         (maintenance_info_program_spaces_command): Update call to
>         print_program_space with new parameter.
> ---
>  gdb/progspace.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/gdb/progspace.c b/gdb/progspace.c
> index a74b6ab..aef2d4e 100644
> --- a/gdb/progspace.c
> +++ b/gdb/progspace.c
> @@ -272,18 +272,19 @@ prune_program_spaces (void)
>
>  /* Prints the list of program spaces and their details on UIOUT.  If
>     REQUESTED is not -1, it's the ID of the pspace that should be
> -   printed.  Otherwise, all spaces are printed.  */
> +   printed.  Otherwise, all spaces are printed.  If PRUNE is true,
> +   prune the unused program spaces prior to printing them, so they
> +   won't be displayed. */
>
>  static void
> -print_program_space (struct ui_out *uiout, int requested)
> +print_program_space (struct ui_out *uiout, int requested, int prune)
>  {
>    struct program_space *pspace;
>    int count = 0;
>    struct cleanup *old_chain;
>
> -  /* Might as well prune away unneeded ones, so the user doesn't even
> -     seem them.  */
> -  prune_program_spaces ();
> +  if (prune)
> +    prune_program_spaces ();
>
>    /* Compute number of pspaces we will print.  */
>    ALL_PSPACES (pspace)
> @@ -385,7 +386,7 @@ maintenance_info_program_spaces_command (char *args, int from_tty)
>         error (_("program space ID %d not known."), requested);
>      }
>
> -  print_program_space (current_uiout, requested);
> +  print_program_space (current_uiout, requested, 0 /* prune */);
>  }
>
>  /* Simply returns the count of program spaces.  */

Hi.

I agree we want to, in general, avoid side-effects in info commands
(even more so in maint info commands).
OTOH, as a reader of this code I wouldn't expect a print routine to
have side-effects either.
IOW, how about move the call to prune_program_spaces to  whatever
caller wants it.

btw, is part of this patch missing?
Is there intended to be another caller of print_program_spaces that
passes prune = 1?
  

On Wednesday, September 24 2014, Doug Evans wrote:

> IOW, how about move the call to prune_program_spaces to  whatever
> caller wants it.

As a note, after I commented on the patch, I noticed that the "prune"
argument may be unecessary indeed (and the "prunning" logic"), because
we are not prunning anything anymore.

Anyway, I just wanted to say that I agree with removing this part of the
code, and moving it to more suitable parts.