[lttng-dev] [PATCH] Rewrites lttng-ctl's set_session_daemon_path(), fix snprintf() return value tests so the code works with both GNU C < 2.1 and >= 2.1

[Thibault, Daniel]

   This fifth patch rewrites lttng-ctl's set_session_daemon_path() to avoid duplicating snippets of code.  It also fixes the snprintf return value test so the code works with both GNU C < 2.1 and >= 2.1.  With GNU C < 2.1, snprintf returns -1 if the target buffer is too small; with GNU C >= 2.1, snprintf returns the required size (excluding the closing null) under the same conditions.

   I do believe it is functionally identical to the version it replaces, but someone should check to make sure.   :-)

------------------------------
>From 3d90c8707c362c9ecf0836c25d500c818ba2e2f0 Mon, 30 Jan 2012 16:25:29 -0500
From: Daniel U. Thibault <daniel.thibault at drdc-rddc.gc.ca>
Date: Mon, 30 Jan 2012 16:25:15 -0500
Subject: [PATCH] Rewrites lttng-ctl's set_session_daemon_path(), fix snprintf() return value tests so the code works with both GNU C < 2.1 and >= 2.1

Signed-off-by: Daniel U. Thibault <daniel.thibault at drdc-rddc.gc.ca>

diff --git a/lttng2-lttng-tools-2.0-pre18+-5c73c59/src/lib/lttng-ctl/lttng-ctl.c b/lttng2-lttng-tools-2.0-pre18+-5c73c59/src/lib/lttng-ctl/lttng-ctl.c
index 537934f..65aa3e3 100644
--- a/lttng2-lttng-tools-2.0-pre18+-5c73c59/src/lib/lttng-ctl/lttng-ctl.c
+++ b/lttng2-lttng-tools-2.0-pre18+-5c73c59/src/lib/lttng-ctl/lttng-ctl.c
@@ -228,35 +228,31 @@
 		in_tgroup = check_tracing_group(tracing_group);
 	}
 
-	if (uid == 0) {
-		/* Root */
+	if ((uid == 0) || in_tgroup) {
 		copy_string(sessiond_sock_path,
 				DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
 				sizeof(sessiond_sock_path));
-	} else if (in_tgroup) {
-		/* Tracing group */
-		copy_string(sessiond_sock_path,
-				DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
-				sizeof(sessiond_sock_path));
-
-		ret = try_connect_sessiond(sessiond_sock_path);
-		if (ret < 0) {
-			/* Global session daemon not available */
-			if (snprintf(sessiond_sock_path, sizeof(sessiond_sock_path),
-						DEFAULT_HOME_CLIENT_UNIX_SOCK,
-						getenv("HOME")) < 0) {
-				return -ENOMEM;
-			}
 		}
-	} else {
-		/* Not in tracing group and not root, default */
-		if (snprintf(sessiond_sock_path, PATH_MAX,
-					DEFAULT_HOME_CLIENT_UNIX_SOCK,
-					getenv("HOME")) < 0) {
+	if (uid != 0) {
+		if (in_tgroup) {
+			/* Tracing group */
+			ret = try_connect_sessiond(sessiond_sock_path);
+			if (ret >= 0) goto end;
+			/* Global session daemon not available... */
+		}
+		/* ...or not in tracing group (and not root), default */
+		/*
+		 * With GNU C <  2.1, snprintf returns -1 if the target buffer is too small;
+		 * With GNU C >= 2.1, snprintf returns the required size (excluding closing null)
+		 */
+		ret = snprintf(sessiond_sock_path, sizeof(sessiond_sock_path),
+				DEFAULT_HOME_CLIENT_UNIX_SOCK,
+				getenv("HOME"));
+		if ((ret < 0) || (ret >= sizeof(sessiond_sock_path))) {
 			return -ENOMEM;
 		}
 	}
-
+end:
 	return 0;
 }

------------------------------

Daniel U. Thibault
R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
Système de systèmes (SdS) / System of Systems (SoS)
Solutions informatiques et expérimentations (SIE) / Computing Solutions and Experimentations (CSE)
2459 Boul. Pie XI Nord
Québec, QC  G3J 1X5
CANADA
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Fax : (418) 844-4538
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Gouvernement du Canada / Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>