[lldb-dev] Watching the current frame locals
Eran Ifrah
eran.ifrah at gmail.com
Tue Apr 8 13:24:42 PDT 2014
On Tue, Apr 8, 2014 at 10:55 PM, Enrico Granata <egranata at apple.com> wrote:
> On Apr 8, 2014, at 12:35 PM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>
> Thanks for the tip. It works fine for 'string' types
> But for simple types (e.g. 'int') GetSummary() returns an empty string.. :/
>
> So I ended up writing this little method:
> http://pastebin.com/pj0znv9j
>
>
> IIUC your logic, you’re saying - for pointers to “char-like things”, get
> the summary, for anything else just get the value
> That doesn’t seem right. You are going to hide the summary for classes and
> structs doing this, and not get anything to display since these don’t have
> a value
>
> Why are you trying to coalesce value and summary instead of keeping them
> as two separate notions and then making print-time decisions?
> In the LLDB source, there is a ValueObjectPrinter.cpp which implements the
> printing that you see with the frame variable command, for instance
> That might be a useful starting point for you to look at if you’re aiming
> to provide “smart” printouts of data
>
> The reason I did this, was that GetSummary() returns empty string in all
cases except for strings, so this was an attempt to merge both columns into
a single column ("Value")
For testing purposes, I updated my UI to include 2 separate columns
"Summary" and "Value"
As you can see in the attached screenshot, the "Summary" is always empty,
except for 'string' types
( I don't see any summary for classes and structs )
http://codelite.org/images/empty-summary.png
> Which seems to work fine for me (ofcourse, I will know more when I upload
> the pre-release to my testers)
>
> Thanks
>
>
>
> On Tue, Apr 8, 2014 at 9:04 PM, <jingham at apple.com> wrote:
>
>> That is what the Summary is for. The Summary, if it exists, is the
>> preferred "interpreted" presentation of the data held by the SBValue. So
>> for a char *, the Value is the pointer value, but the Summary is the
>> c-string contents.
>>
>> Jim
>>
>> On Apr 8, 2014, at 10:57 AM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>>
>> > Hello Enrico / All,
>> >
>> > I debugged it and it seems like a bug in my code.
>> > To get the frame locals (function args and locals) I was using this
>> call:
>> >
>> > frame.GetBlock().GetVariables()
>> >
>> > While I should have simply call to frame.GetVariables()
>> > Which fixes the problem.
>> >
>> > However, I am facing another issue:
>> > It seems like the function "const char* SBValue::GetValue()" returns
>> the pointer address as string instead of the actual content
>> >
>> > Any quick way to get the data as an actual c-str?
>> >
>> > For example:
>> >
>> > int main(int argc, char** argv) {
>> > return 0;
>> > }
>> >
>> > My lldb UI for the "locals" view looks like this (best viewed in
>> monospace font ;)) :
>> >
>> >
>> --------------------------------------------------------------------------------
>> > name | type | value
>> >
>> --------------------------------------------------------------------------------
>> > argc | int | 1
>> > argv | const char** | 0xfffffab123 (some random address)
>> > | | |
>> > +-*argv | const char* | 0xfffffab124 (some other address)
>> > | | |
>> > +- **argv| char | '/'
>> >
>> > In the code, I can identify that *argv is of type
>> lldb::eBasicType*Char, however, I can't find a way to extract the string
>> itself (it should be "/home/eran/test/TestLLDB")
>> >
>> > Any hints?
>> >
>> > Thanks!
>> >
>> >
>> >
>> >
>> > On Mon, Apr 7, 2014 at 5:31 AM, Eran Ifrah <eran.ifrah at gmail.com>
>> wrote:
>> > Thanks, will debug this and see where it fails
>> >
>> > Eran
>> >
>> >
>> > On Mon, Apr 7, 2014 at 1:43 AM, Enrico Granata <egranata at apple.com>
>> wrote:
>> > Yeah the const char* definitely should have a value.
>> > I am guessing the variable is in scope all right. Does it have a
>> summary if you ask for that?
>> > Does the same API call work if you stop directly within LLDB and use
>> the Python API?
>> > More context (e.g. a repro case) would also help - or maybe if you can
>> step through the LLDB code and see where we fail. If these are just frame
>> locals I expect the relevant code to be in ValueObject.cpp GetValueAsCString
>> >
>> > Sent from the iPhone of
>> > Enrico Granata <egranata@🍎.com>
>> >
>> > On Apr 6, 2014, at 12:26 PM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>> >
>> >> One of the local variables was 'const char*' so I would expect it to
>> have a value and others were of type of 'wxString'
>> >> In the UI I expanded all the way to the _M_data which is of type
>> 'wchar_t*' - and still nothing
>> >>
>> >> Eran
>> >>
>> >>
>> >>
>> >> On Sun, Apr 6, 2014 at 9:13 PM, Enrico Granata <egranata at apple.com>
>> wrote:
>> >> What is the data type of your variables?
>> >>
>> >> If they are aggregate types (structs, classes, ...) they won't have a
>> value.
>> >>
>> >> Only basic types (int, float, char, ..., you get the idea - and
>> pointers) have a value.
>> >>
>> >> For other types, they might have a summary, or they might have
>> children, but definitely no value.
>> >>
>> >> Sent from the iPhone of
>> >> Enrico Granata <egranata@🍎.com>
>> >>
>> >> On Apr 6, 2014, at 7:02 AM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>> >>
>> >>> Hello all,
>> >>>
>> >>> I am at a phase where I want to display the current frame local
>> variables whenever the debugger "stops"
>> >>> I was able to get a list of the selected frame's variables in the
>> following manner:
>> >>>
>> >>> lldb::SBFrame frame =
>> m_target.GetProcess().GetSelectedThread().GetSelectedFrame();
>> >>> ...
>> >>> lldb::SBValueList args = frame.GetBlock().GetVariables(m_target,
>> true, true, false);
>> >>> for(size_t i=0; i<args.GetSize(); ++i) {
>> >>> lldb::SBValue value = args.GetValueAtIndex(i);
>> >>> if ( value.IsValid() ) {
>> >>> LLDBLocalVariable::Ptr_t var( new
>> LLDBLocalVariable(value) );
>> >>> locals.push_back( var );
>> >>> }
>> >>> }
>> >>>
>> >>> Now, LLDBLocalVariable is a thin wrapper class for UI purposes.
>> >>> What it does is basically copies values from lldb::SBValue:
>> >>>
>> >>> LLDBLocalVariable::LLDBLocalVariable(lldb::SBValue value) {
>> >>> SetName( value.GetName() );
>> >>> SetType( value.GetTypeName() );
>> >>> SetValue( value.GetValue() ); // always returns null
>> >>> ... // code that handles children of value
>> >>> }
>> >>>
>> >>> value.GetName() and value.GetTypeName() are working as expected (i.e.
>> I get the correct type name and its name)
>> >>> However, I can't get the value as "string". I was naive enough to
>> think that const char* SBValue::GetValue() will do the trick... but this
>> always returns NULL.
>> >>>
>> >>> Any suggestions on what am I doing wrong? an example on how to
>> extract the variable's value in string format will be really appreciated
>> >>>
>> >>> Thanks,
>> >>>
>> >>> P.S.
>> >>> This is Linux 13.10 / 64 bit
>> >>> Self compiled lldb
>> >>>
>> >>> --
>> >>> Eran Ifrah
>> >>> Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> >>> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> >>> _______________________________________________
>> >>> lldb-dev mailing list
>> >>> lldb-dev at cs.uiuc.edu
>> >>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>> >>
>> >>
>> >>
>> >> --
>> >> Eran Ifrah
>> >> Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> >> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> >
>> >
>> >
>> > --
>> > Eran Ifrah
>> > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> >
>> >
>> >
>> > --
>> > Eran Ifrah
>> > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> > _______________________________________________
>> > lldb-dev mailing list
>> > lldb-dev at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>>
>>
>
>
> --
> Eran Ifrah
> Author of codelite, a cross platform open source C/C++ IDE:
> http://www.codelite.org
> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>
>
> *- Enrico*
> 📩 egranata@.com ☎️ 27683
>
>
>
>
--
Eran Ifrah
Author of codelite, a cross platform open source C/C++ IDE:
http://www.codelite.org
wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
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