[binutils-gdb] [gdb/server] Emit warning for SIGINT failure

[binutils-gdb] [gdb/server] Emit warning for SIGINT failure

[Tom de Vries]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4c35c4c6a779c79e456b7a5311f74aafc9026bd5

commit 4c35c4c6a779c79e456b7a5311f74aafc9026bd5
Author: Tom de Vries <tdevries@suse.de>
Date:   Sun Nov 27 10:31:50 2022 +0100

    [gdb/server] Emit warning for SIGINT failure
    
    Consider the executable from test-case gdb.base/interrupt-daemon.exp.
    
    When starting it using gdbserver:
    ...
    $ ./build/gdbserver/gdbserver localhost:2345 \
      ./outputs/gdb.base/interrupt-daemon/interrupt-daemon
    ...
    and connecting to it using gdb:
    ...
    $ gdb -q -ex "target remote localhost:2345" \
        -ex "set follow-fork-mode child" \
        -ex "break daemon_main" -ex cont
    ...
    we are setup to do the same as in the test-case: interrupt a running inferior
    using ^C.
    
    So let's try:
    ...
    (gdb) continue
    Continuing.
    ^C
    ...
    After pressing ^C, nothing happens.  This a known problem, filed as
    PR remote/18772.
    
    The problem is that in linux_process_target::request_interrupt, a kill is used
    to send a SIGINT, but it fails.  And it fails silently.
    
    Make the failure verbose by adding a warning, such that the gdbserver output
    becomes more helpful:
    ...
    Process interrupt-daemon created; pid = 15068
    Listening on port 2345
    Remote debugging from host ::1, port 35148
    Detaching from process 15068
    Detaching from process 15085
    gdbserver: Sending SIGINT to process group of pid 15068 failed: \
      No such process
    ...
    
    Note that the failure can easily be reproduced using the test-case and target
    board native-gdbserver:
    ...
    (gdb) continue^M
    Continuing.^M
    PASS: gdb.base/interrupt-daemon.exp: fg: continue
    ^CFAIL: gdb.base/interrupt-daemon.exp: fg: ctrl-c stops process (timeout)
    ...
    as reported in PR server/23382.
    
    Tested on x86_64-linux.
    Approved-By: Simon Marchi <simon.marchi@efficios.com>

Diff:
---
 gdbserver/linux-low.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index a896b37528b..6f96e16d6f0 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -5467,7 +5467,10 @@ linux_process_target::request_interrupt ()
 {
   /* Send a SIGINT to the process group.  This acts just like the user
      typed a ^C on the controlling terminal.  */
-  ::kill (-signal_pid, SIGINT);
+  int res = ::kill (-signal_pid, SIGINT);
+  if (res == -1)
+    warning (_("Sending SIGINT to process group of pid %ld failed: %s"),
+	     signal_pid, safe_strerror (errno));
 }
 
 bool