[PATCH] gdb/testsuite: use `kill -FOO` instead of `kill -SIGFOO`

[Simon Marchi <simon.marchi@efficios.com>]

When running gdb.base/bg-exec-sigint-bp-cond.exp when SHELL is dash,
rather than bash, I get:

    c&^M
    Continuing.^M
    (gdb) sh: 1: kill: Illegal option -S^M
    ^M
    Breakpoint 2, foo () at /home/jenkins/smarchi/binutils-gdb/build/gdb/testsuite/../../../gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.c:23^M
    23        return 0;^M
    FAIL: gdb.base/bg-exec-sigint-bp-cond.exp: no force memory write: SIGINT does not interrupt background execution (timeout)

This is because it uses the kill command built-in the dash shell, and
using the SIG prefix with kill does not work with dash's kill.  The
difference is listed in the documentation for bash's POSIX-correct mode
[1]:

    The kill builtin does not accept signal names with a ‘SIG’ prefix.

Replace SIGINT with INT in that test.

By grepping, I found two other instances (gdb.base/sigwinch-notty.exp
and gdb.threads/detach-step-over.exp).  Those were not problematic on my
system though.  Since they are done through remote_exec, they don't go
through the shell and therefore invoke /bin/kill.  On my Arch Linux,
it's:

    $ /bin/kill --version
    kill from util-linux 2.38.1 (with: sigqueue, pidfd)

and on my Ubuntu:

    $ /bin/kill --version
    kill from procps-ng 3.3.17

These two implementations accept "-SIGINT".  But according to the POSIX
spec [2], the kill utility should recognize the signal name without the
SIG prefix (if it recognizes them with the SIG prefix, it's an
extension):

    -s  signal_name
        Specify the signal to send, using one of the symbolic names defined
	in the <signal.h> header. Values of signal_name shall be recognized
	in a case-independent fashion, without the SIG prefix. In addition,
	the symbolic name 0 shall be recognized, representing the signal
	value zero. The corresponding signal shall be sent instead of SIGTERM.
    -signal_name
        [XSI] [Option Start]
        Equivalent to -s signal_name. [Option End]

So, just in case some /bin/kill implementation happens to not recognize
the SIG prefixes, change these two other calls to remove the SIG
prefix.

[1] https://www.gnu.org/software/bash/manual/html_node/Bash-POSIX-Mode.html
[2] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/kill.html

Change-Id: I81ccedd6c9428ab63b9261813f1905a18941f8da
---
 gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.exp | 2 +-
 gdb/testsuite/gdb.base/sigwinch-notty.exp         | 2 +-
 gdb/testsuite/gdb.threads/detach-step-over.exp    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.exp b/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.exp
index a8764a4e5ea1..b55c8d305b71 100644
--- a/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.exp
+++ b/gdb/testsuite/gdb.base/bg-exec-sigint-bp-cond.exp
@@ -51,7 +51,7 @@ proc test { {after_kill_cond ""} } {
     # emulates pressing Ctrl-C just while GDB is evaluating the breakpoint
     # condition.
     gdb_test \
-	"break foo if \$hit_count\+\+ == $num_hits || \$_shell(\"kill -SIGINT $gdb_pid\") != 0 $after_kill_cond" \
+	"break foo if \$hit_count\+\+ == $num_hits || \$_shell(\"kill -INT $gdb_pid\") != 0 $after_kill_cond" \
 	"Breakpoint .*" \
 	"break foo if <condition>"
 
diff --git a/gdb/testsuite/gdb.base/sigwinch-notty.exp b/gdb/testsuite/gdb.base/sigwinch-notty.exp
index 99fb1c9a99ee..0be07910228f 100644
--- a/gdb/testsuite/gdb.base/sigwinch-notty.exp
+++ b/gdb/testsuite/gdb.base/sigwinch-notty.exp
@@ -49,7 +49,7 @@ after 1000 {
     # Note, GDB is started under a shell, so PID is actually the
     # shell's pid, not GDB's.  Use "-PID" to send the signal to the
     # whole process group and reach GDB, instead of just to the shell.
-    remote_exec host "kill -SIGWINCH -${gdb_pid}"
+    remote_exec host "kill -WINCH -${gdb_pid}"
 }
 
 # If GDB mishandles the SIGWINCH and crashes, that happens before we
diff --git a/gdb/testsuite/gdb.threads/detach-step-over.exp b/gdb/testsuite/gdb.threads/detach-step-over.exp
index bf5ef6b06a1b..345c77e2c690 100644
--- a/gdb/testsuite/gdb.threads/detach-step-over.exp
+++ b/gdb/testsuite/gdb.threads/detach-step-over.exp
@@ -285,7 +285,7 @@ proc_with_prefix test_detach_command {condition_eval target_non_stop non_stop di
 		# over, then threads of other inferiors should be
 		# re-resumed.  Test for that by sending a signal to
 		# inferior 2.
-		remote_exec target "kill -SIGUSR1 ${pid_inf2}"
+		remote_exec target "kill -USR1 ${pid_inf2}"
 
 		gdb_test_multiple "" "stop with SIGUSR1" {
 		    -re "received signal SIGUSR1" {
-- 
2.39.2