[lldb-dev] Watching the current frame locals

[Eran Ifrah]

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
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