[Bug python/14373] New: std::vector

[Bug python/14373] New: std::vector

[andreasheimberger at gmx dot at]

http://sourceware.org/bugzilla/show_bug.cgi?id=14373

             Bug #: 14373
           Summary: std::vector
           Product: gdb
           Version: 7.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: python
        AssignedTo: unassigned@sourceware.org
        ReportedBy: andreasheimberger@gmx.at
    Classification: Unclassified


Created attachment 6537
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6537
vector gdb frozen

Having an unitialized std::vector gdb freezes and doesn't respond anyway.
Especially when you call -var-list-children in the line where std::vector is
still uninitialized.

Example: 
Code                              GDB
------------------------------------------------------------------------------
std::vector<int> vec;             <<  -var-create - * vec  
                                  <<  -var-list-children var1
vec.push_back(1);
-------------------------------------------------------------------------------

Within Eclipse CDT they must have some implementation that debugging is still
available.

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[Bug python/14373] std::vector

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14373

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at redhat dot com

--- Comment #1 from Tom Tromey <tromey at redhat dot com> 2012-07-20 19:45:24 UTC ---
First, I agree it would be good to be able to interrupt
gdb when it gets wedged like this.

However, the problem here is that the varobj has
many children -- in my test, 105312 of them (but obviously
YMMV).

Front ends are supposed to limit dynamic varobj output
using the provided controls, like -var-set-update-range
or the optional arguments to -var-list-children.
Otherwise, bad things will happen.

In this case, the vector is uninitialized, causing problems.
But the same problems can occur due to other bugs in the program
(trashing the heap), or just if the program happens to create
a really huge data structure -- not unheard-of.

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[Bug python/14373] std::vector

[andreasheimberger at gmx dot at]

http://sourceware.org/bugzilla/show_bug.cgi?id=14373

--- Comment #2 from andreasheimberger at gmx dot at 2012-07-23 08:22:29 UTC ---
I agree to you that it is better to set an update range, also for the other
cases you mentioned. However is there no possibility to check if the variable
is unitialized, or do you know if a feature like that will be implemented in
future? Eventually from gcc perspective.

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[Bug python/14373] std::vector

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14373

--- Comment #3 from Tom Tromey <tromey at redhat dot com> 2012-07-25 15:36:43 UTC ---
(In reply to comment #2)
> I agree to you that it is better to set an update range, also for the other
> cases you mentioned. However is there no possibility to check if the variable
> is unitialized, or do you know if a feature like that will be implemented in
> future? Eventually from gcc perspective.

It may be possible to do this in gcc -- there was one attempt already, see
DW_OP_GNU_uninit -- but I think it is not a good approach, for the reasons
already outlined.

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[Bug python/14373] std::vector

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=14373

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |NOTABUG
             Status|NEW                         |RESOLVED
                 CC|                            |tromey at sourceware dot org

--- Comment #4 from Tom Tromey <tromey at sourceware dot org> ---
I'm going to mark this one as not a bug.
There isn't much gdb can or should do about uninitialized memory.
Front ends can limit the number of varobj children, and should
do so for exactly this reason.

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