[binutils-gdb] [gdb/remote] Use sevenbit_strings == true in escape_buffer

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=7e9614552f205e417366357562afbd21b8d07c29

commit 7e9614552f205e417366357562afbd21b8d07c29
Author: Tom de Vries <[email protected]>
Date:   Wed Mar 25 08:03:01 2026 +0100

    [gdb/remote] Use sevenbit_strings == true in escape_buffer
    
    With Fedora RH, using Tcl 9.0.2, I run into:
    ...
    (gdb) break -q main^M
    [remote] Sending packet: $qXfer:auxv:read::0,1000#6b^M
    [remote] Packet received: l!\000\000\000\000\000\000\000\000 ERROR: \
      i_read(spawn_id fd=9): invalid or incomplete multibyte or wide character
      ...
    UNRESOLVED: gdb.server/bkpt-other-inferior.exp: inf 2: set breakpoint
    ...
    
    For reference, on openSUSE Leap 16.0, with Tcl 8.6.15 the initial part of the
    problematic string looks like:
    ...
    [remote] Packet received: l!\000\000\000\000\000\000\000\000`ü÷ÿ\177\000...
    ...
    
    With Tcl 9.0, something (dejagnu/expect/gdb testsuite infrastructure)
    has problems with gdb IO containing non-utf-8 chars.
    
    Having said that, I don't think having chars like 'ü' in the debug output is
    particularly helpful.
    
    Fix this by forcing sevenbit_strings to true in escape_buffer, getting us
    instead:
    ...
    [remote] Packet received: \
      l!\000\000\000\000\000\000\000\000`\374\367\377\177\000...
    ...
    
    This also fixes test-case gdb.python/py-send-packet.exp, where we run into a
    similar problem with the "Sending packet:" line.
    
    Tested on x86_64-linux, with Tcl 9.0.2 and 8.6.15.
    
    A v1 submitted was submitted here [2].
    
    Changes in v2 [3]:
    - use c_isprint instead of std::isprint
    - use string_appendf instead of std::ostringstream
    
    Changes in v3:
    - Rather than re-implementing escape_buffer, change it to use
      sevenbit_strings == true.
    - update $subject to indicate new approach
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34012
    
    Approved-By: Tom Tromey <[email protected]>
    
    [1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/General-Query-Packets.html#index-qXfer-packet
    [2] v1 https://sourceware.org/pipermail/gdb-patches/2026-March/226110.html
    [3] v2 https://sourceware.org/pipermail/gdb-patches/2026-March/226119.html

Diff:
---
 gdb/remote.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index e84a0dc578b..3ec56a6d61b 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -10509,14 +10509,20 @@ remote_target::remote_serial_send_break ()
 }
 
 /* Return a string representing an escaped version of BUF, of len N.
-   E.g. \n is converted to \\n, \t to \\t, etc.  */
+   E.g. '\n' is converted to R"(\012)", '\t' to R"(\011)", etc.  */
 
 static std::string
 escape_buffer (const char *buf, int n)
 {
   string_file stb;
 
+  /* Temporarily set sevenbit_strings to true to make sure that we print
+     chars >= 0x80 as octal escape \ooo, independent of the current
+     sevenbit_strings setting.  This conservative choice is appropriate for
+     debug logs.  */
+  scoped_restore reset = make_scoped_restore (&sevenbit_strings, true);
   stb.putstrn (buf, n, '\\');
+
   return stb.release ();
 }