[binutils-gdb] Fix qRcmd error code parsing

[Luis Machado <luisgpm@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d5ce6f2dcacf9809fb7a29a69c4b98e0320c3c94

commit d5ce6f2dcacf9809fb7a29a69c4b98e0320c3c94
Author: Luis Machado <luis.machado@arm.com>
Date:   Thu Mar 31 16:45:53 2022 +0100

    Fix qRcmd error code parsing
    
    Someone at IRC spotted a bug in qRcmd handling. This looks like an oversight
    or it is that way for historical reasons.
    
    The code in gdb/remote.c:remote_target::rcmd uses isdigit instead of
    isxdigit. One could argue that we are expecting decimal numbers, but further
    below we use fromhex ().
    
    Update the function to use isxdigit instead and also update the documentation.
    
    I see there are lots of other cases of undocumented number format for error
    messages, mostly described as NN instead of nn. For now I'll just update
    this particular function.

Diff:
---
 gdb/doc/gdb.texinfo | 3 ++-
 gdb/remote.c        | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index b7da5e1173b..e50618fe9ab 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -42157,7 +42157,8 @@ A command response with no output.
 @item @var{OUTPUT}
 A command response with the hex encoded output string @var{OUTPUT}.
 @item E @var{NN}
-Indicate a badly formed request.
+Indicate a badly formed request.  The error number @var{NN} is given as
+hex digits.
 @item @w{}
 An empty reply indicates that @samp{qRcmd} is not recognized.
 @end table
diff --git a/gdb/remote.c b/gdb/remote.c
index 122f204fe12..b002f041734 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -11565,7 +11565,7 @@ remote_target::rcmd (const char *command, struct ui_file *outbuf)
       if (strcmp (buf, "OK") == 0)
 	break;
       if (strlen (buf) == 3 && buf[0] == 'E'
-	  && isdigit (buf[1]) && isdigit (buf[2]))
+	  && isxdigit (buf[1]) && isxdigit (buf[2]))
 	{
 	  error (_("Protocol error with Rcmd"));
 	}