[PATCH 3/3] Eliminate STOP_SIGNAL, use SIGTSTP directly

Pedro Alves
2017-11-02T15:12:14Z

The STOP_SIGNAL macro was originally added for Convex Unix [1]:

In:

git show 7a67dd45ca1c:gdb/m-convex.h

we see:

~~~
/* Use SIGCONT rather than SIGTSTP because convex Unix occasionally
turkeys SIGTSTP. I think. */

#define STOP_SIGNAL SIGCONT
~~~

That's gdb-3.5, 1990... In gdb/ChangeLog-3.x we see:

~~~
Tue Apr 18 13:43:37 1989 Randall Smith (randy at apple-gunkies.ai.mit.edu)

Various changes involved in 1) getting gdb to work on the convex,
[...]
Made whatever signal indicates a stop configurable (via macro
STOP_SIGNAL).
(main): Setup use of above as a signal handler. Added check for
"-nw" in args already processed.
(command_line_input): SIGTSTP ==>STOP_SIGNAL.
~~~

Support for Convex Unix is long gone, and nothing else overrides
STOP_SIGNAL. So just use SIGTSTP directly, removing a little
obfuscation.

(I don't really understand why we override [1] readline's SIGTSTP
handler (only) when reading scripts (and then fail to restore it
properly, assuming SIG_DFL...), but I'll leave that for another pass.

[1] - Actually, starting with readline 6.3, readline is no longer
installing its handlers while GDB is in control...)

gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>

* event-top.c: Check SIGTSTP instead of STOP_SIGNAL thoughout.
(async_init_signals): Adjust.
(handle_stop_sig): Rename to ...
(handle_sigtstp): ... this.
(async_stop_sig): Rename to ...
(async_sigtstp_handler): ... this, and delete STOP_SIGNAL !=
SIGTSTP path.
* event-top.h: Move signal.h include to the top. Check SIGTSTP
instead of STOP_SIGNAL thoughout.
(handle_stop_sig): Rename to ...
(handle_sigtstp): ... this.
* top.c (command_line_input): Replace STOP_SIGNAL -> SIGTSTP.
---
gdb/event-top.c | 26 +++++++++++---------------
gdb/event-top.h | 10 ++++------
gdb/top.c | 8 ++++----
3 files changed, 19 insertions(+), 25 deletions(-)

diff --git a/gdb/event-top.c b/gdb/event-top.c
index 43e2a27..7377189 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -68,8 +68,8 @@ static void async_do_nothing (gdb_client_data);
static void async_disconnect (gdb_client_data);
#endif
static void async_float_handler (gdb_client_data);
-#ifdef STOP_SIGNAL
-static void async_stop_sig (gdb_client_data);
+#ifdef SIGTSTP
+static void async_sigtstp_handler (gdb_client_data);
#endif
static void async_sigterm_handler (gdb_client_data arg);

@@ -111,7 +111,7 @@ static struct async_signal_handler *sighup_token;
static struct async_signal_handler *sigquit_token;
#endif
static struct async_signal_handler *sigfpe_token;
-#ifdef STOP_SIGNAL
+#ifdef SIGTSTP
static struct async_signal_handler *sigtstp_token;
#endif
static struct async_signal_handler *async_sigterm_token;
@@ -912,9 +912,9 @@ async_init_signals (void)
sigfpe_token =
create_async_signal_handler (async_float_handler, NULL);

-#ifdef STOP_SIGNAL
+#ifdef SIGTSTP
sigtstp_token =
- create_async_signal_handler (async_stop_sig, NULL);
+ create_async_signal_handler (async_sigtstp_handler, NULL);
#endif
}

@@ -1112,20 +1112,19 @@ async_disconnect (gdb_client_data arg)
}
#endif

-#ifdef STOP_SIGNAL
+#ifdef SIGTSTP
void
-handle_stop_sig (int sig)
+handle_sigtstp (int sig)
{
mark_async_signal_handler (sigtstp_token);
- signal (sig, handle_stop_sig);
+ signal (sig, handle_sigtstp);
}

static void
-async_stop_sig (gdb_client_data arg)
+async_sigtstp_handler (gdb_client_data arg)
{
char *prompt = get_prompt ();

-#if STOP_SIGNAL == SIGTSTP
signal (SIGTSTP, SIG_DFL);
#if HAVE_SIGPROCMASK
{
@@ -1138,10 +1137,7 @@ async_stop_sig (gdb_client_data arg)
sigsetmask (0);
#endif
raise (SIGTSTP);
- signal (SIGTSTP, handle_stop_sig);
-#else
- signal (STOP_SIGNAL, handle_stop_sig);
-#endif
+ signal (SIGTSTP, handle_sigtstp);
printf_unfiltered ("%s", prompt);
gdb_flush (gdb_stdout);

@@ -1149,7 +1145,7 @@ async_stop_sig (gdb_client_data arg)
nothing. */
dont_repeat ();
}
-#endif /* STOP_SIGNAL */
+#endif /* SIGTSTP */

/* Tell the event loop what to do if SIGFPE is received.
See event-signal.c. */
diff --git a/gdb/event-top.h b/gdb/event-top.h
index 05241ad..d069c56 100644
--- a/gdb/event-top.h
+++ b/gdb/event-top.h
@@ -22,6 +22,8 @@
#ifndef EVENT_TOP_H
#define EVENT_TOP_H

+#include <signal.h>
+
struct cmd_list_element;

/* Exported functions from event-top.c.
@@ -36,14 +38,10 @@ extern void change_line_handler (int);
extern void command_line_handler (char *rl);
extern void command_handler (char *command);

-/* Signal to catch ^Z typed while reading a command: SIGTSTP or SIGCONT. */
-#ifndef STOP_SIGNAL
-#include <signal.h>
#ifdef SIGTSTP
-#define STOP_SIGNAL SIGTSTP
-extern void handle_stop_sig (int sig);
-#endif
+extern void handle_sigtstp (int sig);
#endif
+
extern void handle_sigint (int sig);
extern void handle_sigterm (int sig);
extern void async_request_quit (void *arg);
diff --git a/gdb/top.c b/gdb/top.c
index 9f5dd58..f006c66 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -1184,9 +1184,9 @@ command_line_input (const char *prompt_arg, int repeat,
/* Starting a new command line. */
cmd_line_buffer.used_size = 0;

-#ifdef STOP_SIGNAL
+#ifdef SIGTSTP
if (job_control)
- signal (STOP_SIGNAL, handle_stop_sig);
+ signal (SIGTSTP, handle_sigtstp);
#endif

while (1)
@@ -1244,9 +1244,9 @@ command_line_input (const char *prompt_arg, int repeat,
prompt = NULL;
}

-#ifdef STOP_SIGNAL
+#ifdef SIGTSTP
if (job_control)
- signal (STOP_SIGNAL, SIG_DFL);
+ signal (SIGTSTP, SIG_DFL);
#endif

return cmd;
--
2.5.5