utils: add subdaemon_shutdown() to consolidate subdaemon cleanup.

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

channeld/channel.c

@@ -2753,6 +2753,6 @@ int main(int argc, char *argv[])
 	/* We only exit when shutdown is complete. */
 	assert(shutdown_complete(peer));
 	send_shutdown_complete(peer);
-	tal_free(tmpctx);
+	subdaemon_shutdown();
 	return 0;
 }

closingd/closing.c

@@ -577,7 +577,7 @@ int main(int argc, char *argv[])
 	wire_sync_write(REQ_FD,
 			take(towire_closing_complete(NULL, gossip_index)));
 	tal_free(ctx);
-	tal_free(tmpctx);
+	subdaemon_shutdown();
 
 	return 0;
 }

common/subdaemon.c

@@ -101,3 +101,9 @@ void subdaemon_setup(int argc, char *argv[])
 	}
 #endif
 }
+
+void subdaemon_shutdown(void)
+{
+	tal_free(tmpctx);
+	secp256k1_context_destroy(secp256k1_ctx);
+}

common/subdaemon.h

@@ -4,4 +4,7 @@
 
 void subdaemon_setup(int argc, char *argv[]);
 
+/* Shutdown for a valgrind-clean exit (frees everything) */
+void subdaemon_shutdown(void);
+
 #endif /* LIGHTNING_COMMON_SUBDAEMON_H */

gossipd/gossip.c

@@ -2147,6 +2147,7 @@ int main(int argc, char *argv[])
 			timer_expired(daemon, expired);
 		}
 	}
+	subdaemon_shutdown();
 	return 0;
 }
 #endif

hsmd/hsm.c

@@ -842,6 +842,8 @@ int main(int argc, char *argv[])
 	/* When conn closes, everything is freed. */
 	tal_steal(client->dc.conn, client);
 	io_loop(NULL, NULL);
+	subdaemon_shutdown();
+
 	return 0;
 }
 #endif

onchaind/onchain.c

@@ -2315,7 +2315,7 @@ int main(int argc, char *argv[])
 
 	/* We're done! */
 	tal_free(ctx);
-	tal_free(tmpctx);
+	subdaemon_shutdown();
 
 	return 0;
 }

openingd/opening.c

@@ -776,7 +776,7 @@ int main(int argc, char *argv[])
 	status_trace("Sent %s with fd",
 		     opening_wire_type_name(fromwire_peektype(msg)));
 	tal_free(state);
-	tal_free(tmpctx);
+	subdaemon_shutdown();
 	return 0;
 }
 #endif /* TESTING */