[Bug mi/11335] New: -var-evaluate-expression should return the pretty printer's to_string result

[Bug mi/11335] New: -var-evaluate-expression should return the pretty printer's to_string result

[jens dot elmenthaler at verigy dot com]

The only way to obtain the value of a dynamic variable objects (= the return 
value of the pretty printer) is -data-evaluate-expresssion. However, -data-
evaluate-expresion cannot be used for children of dynamic variable objects, 
since it is impossible to provide the required expression.

The same should possibly returned in the results of -var-update and -var-list-
children.

-- 
           Summary: -var-evaluate-expression should return the pretty
                    printer's to_string result
           Product: gdb
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: mi
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: jens dot elmenthaler at verigy dot com
                CC: gdb-prs at sourceware dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[vladimir at codesourcery dot com]

------- Additional Comments From vladimir at codesourcery dot com  2010-03-06 08:14 -------
Could you clarify why you even want to use -data-evaluate-expression? Is that
because you're adding pretty-printing to CDT and CDT, for some unknown reason,
wants to display "variable details" for selected node in the variables tree?

I am opposed to bloating the output of -var-update and or -var-list-children
with full text (=CLI) rendering of that varobj, because such a design would
require that GDB, fetches entire value from memory, always. It might be
possible to introduce a separate command, or add --varobj option to -data-

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http://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[vladimir at codesourcery dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vladimir at codesourcery dot
                   |                            |com


http://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[jens dot elmenthaler at verigy dot com]

------- Additional Comments From jens dot elmenthaler at verigy dot com  2010-03-07 13:34 -------
Ok, I know it again. The problem was for pretty printers returning children.

For instance, I have a collection and the pretty printer has a to_string 
method returning a summary (like "vector of lenght 2"). I would like to show 
this summary in the value column. -var-evaluate-expression only 
returns "{...}", probably since it has children. The only way of retrieving 
the summary, then, is to ask -data-evaluate-expression. But this works only as 
long as I'm able to provide the required expression, which I can only do as 
long as the variable of interest is not a child of another dynamic variable.

So my request simply was that -var-evaluate-expression returns the result of 
the to_string method if it is backed by a pretty printer, regardless of 
whether it has children or not.

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[vladimir at codesourcery dot com]

------- Additional Comments From vladimir at codesourcery dot com  2010-03-29 20:42 -------
I actually though that this summary is both too huge and not particularly
useful in a frontend. Say, the type of container is already knows, so all
the summary say is report the size. Maybe, for containers, we want to show
[N] as opposed to {...}?

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http://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[jens dot elmenthaler at verigy dot com]

------- Additional Comments From jens dot elmenthaler at verigy dot com  2010-03-30 07:20 -------
(In reply to comment #3)
> I actually though that this summary is both too huge and not particularly
> useful in a frontend. Say, the type of container is already knows, so all
> the summary say is report the size. Maybe, for containers, we want to show
> [N] as opposed to {...}?
Yes, from the requirements point, this is what I miss most. Currently, I have 
to expand the collection variable, if I just want to see how many elements it 
contains. And this doesn't work well, because in a large collection I also 
have to scroll to the end.

Lets assume your proposal, how would you decide it's a collection? You take 
the display hint and if it's map or vector, it's collection. Next, how will 
you determine the number of childen? You cannot use the children method and 
use the iterate over all elements. If the collection is uninitialized, it may 
never return. Alternatively, you could add a new method to the pretty printers.

It all boyls down to what our understanding of the to_string method is. Shall 
it just provide a short summary to identify an object, or shall it be used to 
dump all members in a string? I always interpreted as the first.

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http://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[krf at gmx dot de]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

Kevin Funk <krf at gmx dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |krf at gmx dot de

--- Comment #5 from Kevin Funk <krf at gmx dot de> ---
Hey Vladimir.

I'm curious if this issue has been solved in one or the other way up to now. I
was wondering if we could resolve those '{...}' for non-simple types in
KDevelop's GDB support, and stumbled upon this bug entry. 

I think it's valid request to get some 'short summary' of non-simple types.
Containers are the best example, it'd be good to know how many items they
contain, without requesting the individual child items.

Given the documentation about the pretty printer's to_string() method:
"When printing from the CLI, if the to_string method exists, then gdb will
prepend its result to the values returned by children. Exactly how this
formatting is done is dependent on the display hint, and may change as more
hints are added. Also, depending on the print settings (see Print Settings),
the CLI may print just the result of to_string in a stack trace, omitting the
result of children."
=> Here, to_string() is used unconditionally, children() is optional. Can't we
transfer that kind of behavior to -var-evaluate-expression and friends as well?

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[vladimir at codesourcery dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

--- Comment #6 from Vladimir Prus <vladimir at codesourcery dot com> ---
Kevin,

I don't know the current status of this issue 100%, but I don't know of any
changes here.

It is generally reasonable to see short summary of composite types, but still,
what do we do if a composite type is big? Iterating over all children just to
count them might be expensive.

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yerimyah1 at gmail dot com

--- Comment #9 from Tom Tromey <tromey at sourceware dot org> ---
*** Bug 28201 has been marked as a duplicate of this bug. ***

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |piel at microsoft dot com

--- Comment #10 from Tom Tromey <tromey at sourceware dot org> ---
*** Bug 25153 has been marked as a duplicate of this bug. ***

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org
                 CC|                            |tromey at sourceware dot org

--- Comment #11 from Tom Tromey <tromey at sourceware dot org> ---
Sending a patch.

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

--- Comment #12 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3e8154778baf4df222d95e43a2c8fefdb17305f7

commit 3e8154778baf4df222d95e43a2c8fefdb17305f7
Author: Tom Tromey <tromey@adacore.com>
Date:   Thu May 26 08:33:05 2022 -0600

    Put pretty-printers to_string output in varobj result

    PR mi/11335 points out that an MI varobj will not display the result
    of a pretty-printer's "to_string" method.  Instead, it always shows
    "{...}".

    This does not seem very useful, and there have been multiple
    complaints about it over the years.  This patch changes varobj to emit
    this string when possible, and updates the test suite.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=11335

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[Bug mi/11335] -var-evaluate-expression should return the pretty printer's to_string result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=11335

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
   Target Milestone|7.1                         |14.1
         Resolution|---                         |FIXED

--- Comment #13 from Tom Tromey <tromey at sourceware dot org> ---
Fixed.

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