Discussion:
GDB/MI escape characters
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Bob Rossi
2014-07-28 01:03:03 UTC
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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
Bob Rossi
2014-07-30 10:45:56 UTC
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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
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