GDB/MI escape characters

GDB/MI escape characters

[Bob Rossi]

Hi,

Does anyone know what characters GDB escapes in the GDB/MI protocol
above and beyond what would otherwise be escaped from the CLI?

For instance if i print the variable p,
    char *p = "aaa\"aaa\naaa\raaa\\aaa";
from the cli I get,
    (gdb) p p
    $1 = 0x400584 "aaa\"aaa\naaa\raaa\\aaa"
from MI I get,
    p p
    ~"$2 = 0x400584 \"aaa\\\"aaa\\naaa\\raaa\\\\aaa\""

From the output I can see that \ and " are escaped in MI output above
and beyond what is escaped in the CLI. Are there other characters that
would be?

The function mi-out.c:mi_field_string might be a clue?

Thanks,
Bob Rossi

Re: GDB/MI escape characters

[Bob Rossi]

On Sun, Jul 27, 2014 at 09:03:03PM -0400, Bob Rossi wrote:
> Hi,
> 
> Does anyone know what characters GDB escapes in the GDB/MI protocol
> above and beyond what would otherwise be escaped from the CLI?
> 
> For instance if i print the variable p,
>     char *p = "aaa\"aaa\naaa\raaa\\aaa";
> from the cli I get,
>     (gdb) p p
>     $1 = 0x400584 "aaa\"aaa\naaa\raaa\\aaa"
> from MI I get,
>     p p
>     ~"$2 = 0x400584 \"aaa\\\"aaa\\naaa\\raaa\\\\aaa\""
> 
> From the output I can see that \ and " are escaped in MI output above
> and beyond what is escaped in the CLI. Are there other characters that
> would be?
> 
> The function mi-out.c:mi_field_string might be a clue?

I've determined that the quoting explicitely happens for c-string's
rules in the grammar here,
  https://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI-Output-Syntax.html#GDB_002fMI-Output-Syntax
 
I was debugging gdb and got to utils.c, this function,
  http://pastie.org/private/hcabdm4q81jdrt4yhpghwg#6
the quoter parameter is ".

So I think I've determined that in general, gdb will escape \ to \\
and " to \" so the gdb/mi client has to undo that. Make sense?

I was pretty suprised to see in that example that the ESC character goes
to \e, but only in some situations.

Thanks,
Bob Rossi