plugins: allow --dev-debugger=<pluginname>.

This currently just invokes GDB, but we could generalize it (though
pdb doesn't allow attaching to a running process, other python
debuggers seem to).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/daemon.c

@@ -4,6 +4,7 @@
 #include <ccan/err/err.h>
 #include <ccan/io/io.h>
 #include <ccan/str/str.h>
+#include <ccan/tal/str/str.h>
 #include <common/daemon.h>
 #include <common/memleak.h>
 #include <common/status.h>
@@ -150,3 +151,23 @@ void daemon_shutdown(void)
 	tal_free(tmpctx);
 	wally_cleanup(0);
 }
+
+void daemon_maybe_debug(int argc, char *argv[])
+{
+#if DEVELOPER
+	for (int i = 1; i < argc; i++) {
+		if (!streq(argv[i], "--debugger"))
+			continue;
+
+		/* Don't let this mess up stdout, so redir to /dev/null */
+		char *cmd = tal_fmt(NULL, "${DEBUG_TERM:-gnome-terminal --} gdb -ex 'attach %u' %s >/dev/null &", getpid(), argv[0]);
+		fprintf(stderr, "Running %s\n", cmd);
+		/* warn_unused_result is fascist bullshit.
+		 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 */
+		if (system(cmd))
+			;
+		/* Continue in the debugger. */
+		kill(getpid(), SIGSTOP);
+	}
+#endif /* DEVELOPER */
+}

common/daemon.h

@@ -14,6 +14,9 @@ int daemon_poll(struct pollfd *fds, nfds_t nfds, int timeout);
 /* Shutdown for a valgrind-clean exit (frees everything) */
 void daemon_shutdown(void);
 
+/* Kick in a debugger if they set --debugger */
+void daemon_maybe_debug(int argc, char *argv[]);
+
 struct backtrace_state *backtrace_state;
 
 #endif /* LIGHTNING_COMMON_DAEMON_H */

common/subdaemon.c

@@ -37,19 +37,10 @@ void subdaemon_setup(int argc, char *argv[])
 			logging_io = true;
 	}
 
+	daemon_maybe_debug(argc, argv);
+
 #if DEVELOPER
-	/* From debugger, set debugger_spin to 0. */
 	for (int i = 1; i < argc; i++) {
-		if (streq(argv[i], "--debugger")) {
-			char *cmd = tal_fmt(NULL, "${DEBUG_TERM:-gnome-terminal --} gdb -ex 'attach %u' %s &", getpid(), argv[0]);
-			fprintf(stderr, "Running %s\n", cmd);
-			/* warn_unused_result is fascist bullshit.
-			 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 */
-			if (system(cmd))
-				;
-			/* Continue in the debugger. */
-			kill(getpid(), SIGSTOP);
-		}
 		if (strstarts(argv[i], "--dev-disconnect=")) {
 			dev_disconnect_init(atoi(argv[i]
 						 + strlen("--dev-disconnect=")));

lightningd/lightningd.c

@@ -110,8 +110,8 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	 * is a nod to keeping it minimal and explicit: we need this code for
 	 * testing, but its existence means we're not actually testing the
 	 * same exact code users will be running. */
+	ld->dev_debug_subprocess = NULL;
 #if DEVELOPER
-	ld->dev_debug_subdaemon = NULL;
 	ld->dev_disconnect_fd = -1;
 	ld->dev_subdaemon_fail = false;
 	ld->dev_allow_localhost = false;
@@ -611,7 +611,7 @@ int main(int argc, char *argv[])
 	/*~ Initialize all the plugins we just registered, so they can
 	 *  do their thing and tell us about themselves (including
 	 *  options registration). */
-	plugins_init(ld->plugins);
+	plugins_init(ld->plugins, ld->dev_debug_subprocess);
 
 	/*~ Handle options and config; move to .lightningd (--lightning-dir) */
 	handle_opts(ld, argc, argv);

lightningd/lightningd.h

@@ -183,10 +183,10 @@ struct lightningd {
 	 * if we are the fundee. */
 	u32 max_funding_unconfirmed;
 
-#if DEVELOPER
+	/* If we want to debug a subdaemon/plugin. */
-	/* If we want to debug a subdaemon. */
+	const char *dev_debug_subprocess;
-	const char *dev_debug_subdaemon;
 
+#if DEVELOPER
 	/* If we have a --dev-disconnect file */
 	int dev_disconnect_fd;
 

lightningd/options.c

@@ -435,6 +435,12 @@ static void config_register_opts(struct lightningd *ld)
 }
 
 #if DEVELOPER
+static char *opt_subprocess_debug(const char *optarg, struct lightningd *ld)
+{
+	ld->dev_debug_subprocess = optarg;
+	return NULL;
+}
+
 static void dev_register_opts(struct lightningd *ld)
 {
 	opt_register_noarg("--dev-no-reconnect", opt_set_invbool,
@@ -442,8 +448,8 @@ static void dev_register_opts(struct lightningd *ld)
 			   "Disable automatic reconnect attempts");
 	opt_register_noarg("--dev-fail-on-subdaemon-fail", opt_set_bool,
 			   &ld->dev_subdaemon_fail, opt_hidden);
-	opt_register_arg("--dev-debugger=<subdaemon>", opt_subd_debug, NULL,
+	opt_register_early_arg("--dev-debugger=<subprocess>", opt_subprocess_debug, NULL,
-			 ld, "Invoke gdb at start of <subdaemon>");
+			 ld, "Invoke gdb at start of <subprocess>");
 	opt_register_arg("--dev-broadcast-interval=<ms>", opt_set_uintval,
 			 opt_show_uintval, &ld->config.broadcast_interval_msec,
 			 "Time between gossip broadcasts in milliseconds");

lightningd/plugin.c

@@ -766,7 +766,7 @@ void clear_plugins(struct plugins *plugins)
 		tal_free(p);
 }
 
-void plugins_init(struct plugins *plugins)
+void plugins_init(struct plugins *plugins, const char *dev_plugin_debug)
 {
 	struct plugin *p;
 	char **cmd;
@@ -778,9 +778,13 @@ void plugins_init(struct plugins *plugins)
 
 	/* Spawn the plugin processes before entering the io_loop */
 	list_for_each(&plugins->plugins, p, list) {
-		cmd = tal_arr(p, char *, 2);
+		bool debug;
+
+		debug = dev_plugin_debug && strends(p->cmd, dev_plugin_debug);
+		cmd = tal_arrz(p, char *, 2 + debug);
 		cmd[0] = p->cmd;
-		cmd[1] = NULL;
+		if (debug)
+			cmd[1] = "--debugger";
 		p->pid = pipecmdarr(&stdout, &stdin, NULL, cmd);
 
 		if (p->pid == -1)
@@ -798,9 +802,15 @@ void plugins_init(struct plugins *plugins)
 		json_array_end(req->stream);
 		plugin_request_queue(req);
 		plugins->pending_manifests++;
-		p->timeout_timer = new_reltimer(
+		/* Don't timeout if they're running a debugger. */
-		    &plugins->timers, p, time_from_sec(PLUGIN_MANIFEST_TIMEOUT),
+		if (debug)
+			p->timeout_timer = NULL;
+		else {
+			p->timeout_timer
+				= new_reltimer(&plugins->timers, p,
+					       time_from_sec(PLUGIN_MANIFEST_TIMEOUT),
 					       plugin_manifest_timeout, p);
+		}
 		tal_free(cmd);
 	}
 

lightningd/plugin.h

@@ -27,8 +27,10 @@ struct plugins *plugins_new(const tal_t *ctx, struct log_book *log_book,
  * arguments. In order to read the getmanifest reply from the plugins
  * we spin up our own io_loop that exits once all plugins have
  * responded.
+ *
+ * The dev_plugin_debug arg comes from --dev-debugger if DEVELOPER.
  */
-void plugins_init(struct plugins *plugins);
+void plugins_init(struct plugins *plugins, const char *dev_plugin_debug);
 
 /**
  * Register a plugin for initialization and execution.

lightningd/subd.c

@@ -626,7 +626,7 @@ static struct subd *new_subd(struct lightningd *ld,
 	assert(name != NULL);
 
 #if DEVELOPER
-	debug_subd = ld->dev_debug_subdaemon;
+	debug_subd = ld->dev_debug_subprocess;
 	disconnect_fd = ld->dev_disconnect_fd;
 #endif /* DEVELOPER */
 
@@ -784,12 +784,6 @@ void subd_release_channel(struct subd *owner, void *channel)
 }
 
 #if DEVELOPER
-char *opt_subd_debug(const char *optarg, struct lightningd *ld)
-{
-	ld->dev_debug_subdaemon = optarg;
-	return NULL;
-}
-
 char *opt_subd_dev_disconnect(const char *optarg, struct lightningd *ld)
 {
 	ld->dev_disconnect_fd = open(optarg, O_RDONLY);

lightningd/subd.h

@@ -206,7 +206,6 @@ void subd_shutdown(struct subd *subd, unsigned int seconds);
 const char *find_my_abspath(const tal_t *ctx, const char *argv0);
 
 #if DEVELOPER
-char *opt_subd_debug(const char *optarg, struct lightningd *ld);
 char *opt_subd_dev_disconnect(const char *optarg, struct lightningd *ld);
 
 bool dev_disconnect_permanent(struct lightningd *ld);

lightningd/test/run-find_my_abspath.c

@@ -136,7 +136,7 @@ void onchaind_replay_channels(struct lightningd *ld UNNEEDED)
 void plugins_config(struct plugins *plugins UNNEEDED)
 { fprintf(stderr, "plugins_config called!\n"); abort(); }
 /* Generated stub for plugins_init */
-void plugins_init(struct plugins *plugins UNNEEDED)
+void plugins_init(struct plugins *plugins UNNEEDED, const char *dev_plugin_debug UNNEEDED)
 { fprintf(stderr, "plugins_init called!\n"); abort(); }
 /* Generated stub for plugins_new */
 struct plugins *plugins_new(const tal_t *ctx UNNEEDED, struct log_book *log_book UNNEEDED,