Re: GDB and GDB/MI different reponses....

Re: GDB and GDB/MI different reponses....

[webquinty quinty]

 Hello,

 As you known, with GDB it is possible to obtain debug information from
 executable.

 For example in GDB you can ask about type of var:

 -> whatis var
 <- type = unsigned char

 I just finished a frontend to extract debug information from a process
 using GDB/MI but the response is different than when I use GDB.

 For example, a struct called 'par' GDB return me type=param_typ but GDB/MI
 return me anonimous struct.

 Why?

 Best regards

Re: GDB and GDB/MI different reponses....

[Pedro Alves]

On 03/21/2013 04:30 PM, webquinty quinty wrote:
>  Hello,
> 
>  As you known, with GDB it is possible to obtain debug information from
>  executable.
> 
>  For example in GDB you can ask about type of var:
> 
>  -> whatis var
>  <- type = unsigned char
> 
>  I just finished a frontend to extract debug information from a process
>  using GDB/MI but the response is different than when I use GDB.
> 
>  For example, a struct called 'par' GDB return me type=param_typ but GDB/MI
>  return me anonimous struct.
> 
>  Why?

This is the sort of question that is simply impossible to answer definitely
without having the binary in question, or even knowing exactly what you have
attempted.  Please don't make us guess; be proactive.  But in principle there
should be no difference.

I'd guess either you've used different GDBs for the CLI vs MI tests, or,
you have more than one 'par' in your program, and depending on current context
(what the current function/frame GDB has selected for inspecting) and perhaps
phase of the moon, you'll get one answer or the other.

-- 
Pedro Alves

Re: GDB and GDB/MI different reponses....

[Pedro Alves]

On 04/04/2013 10:05 AM, John Martin wrote:

> Perhaps it isn't enough information.
> 
> I have fixed the problem but I don't understand  how to do it.
> 
> If I execute the follow command:
> "gdb --interpreter=mi --readnow"  then I have several anonimous structs.
> 
> But if I call gdb without "--readnow" argument, then GDB/MI return me correct structs types.

Okay, then MI seems to be a red herring.  You should see the
same (--readnow vs no --readnow) with the CLI?

> What is "--readnow"?

From gdb --help:

  --readnow          Fully read symbol files on first access.

Reading debug info is a slow process, and without that switch (the
default), GDB will read in debug info lazily, as necessary.
It is not advisable to use --readnow.  It's mostly useful for
debugging/testing gdb's debug info read speed.

In principle, that switch should not cause user visible behavior
change.  But if you have more than one variable with the same name
in your program, reading in all debug info preemptively could
change which variable happens to find first (this is the kind of
thing I was referring to as "phase of the moon", btw).  I think
we have bug reports open around this.

-- 
Pedro Alves