Dump values from FPU after each operation

Dump values from FPU after each operation

[Thomas Baruchel]

Hi, I have a compiled program with no debugging symbol (and no source if
you want to ask). I would like to know how some floating point value is
made of, and since I know what value I am looking for, I think one easy
way would be to lauch the program and to have on the standard output the
content of the FPU after each operation; I am aware it will be a huge
amount of value, but since I know which value is expected, I could
probably parse this output to grep (with -A / -B options in order to extract
100 lines around the exact matching). But is it possible to do such a thing?

I am aware that dumping these registers will not tell me the operations,
but this is not a big issue; I can probably guess it once I know the
involved floating-point values.

If the data can't be redirect to standard output, I can save it, this is not
the most important. Regards,

-- 
Thomas Baruchel

Re: Dump values from FPU after each operation

[Eli Zaretskii]

> Date: Fri, 4 Nov 2011 09:14:35 +0100 (CET)
> From: Thomas Baruchel <baruchel@gmx.com>
> 
> Hi, I have a compiled program with no debugging symbol (and no source if
> you want to ask). I would like to know how some floating point value is
> made of, and since I know what value I am looking for, I think one easy
> way would be to lauch the program and to have on the standard output the
> content of the FPU after each operation; I am aware it will be a huge
> amount of value, but since I know which value is expected, I could
> probably parse this output to grep (with -A / -B options in order to extract
> 100 lines around the exact matching). But is it possible to do such a thing?
> 
> I am aware that dumping these registers will not tell me the operations,
> but this is not a big issue; I can probably guess it once I know the
> involved floating-point values.
> 
> If the data can't be redirect to standard output, I can save it, this is not
> the most important. Regards,

I think you want "info float" and/or "info all-registers", and you
want to turn on logging, so GDB writes everything to a log file you
can later process.

Re: Dump values from FPU after each operation

[Thomas Baruchel]

On Fri, 4 Nov 2011, Eli Zaretskii wrote:
> I think you want "info float" and/or "info all-registers", and you
> want to turn on logging, so GDB writes everything to a log file you
> can later process.

OK, is there a way to have the content of the floating point registers
printed as float rather than in hexadecimal? Regards,

-- 
Thomas Baruchel

Re: Dump values from FPU after each operation

[Eli Zaretskii]

> Date: Fri, 4 Nov 2011 17:46:16 +0100 (CET)
> From: Thomas Baruchel <baruchel@gmx.com>
> 
> On Fri, 4 Nov 2011, Eli Zaretskii wrote:
> > I think you want "info float" and/or "info all-registers", and you
> > want to turn on logging, so GDB writes everything to a log file you
> > can later process.
> 
> OK, is there a way to have the content of the floating point registers
> printed as float rather than in hexadecimal? Regards,

"info all-registers" does that.