diff mbox series

[Openvpn-devel,v4] Silence compiler truncation warning by checking snprintf return value

Message ID 20260121121830.27244-1-frank@lichtenheld.com
State New
Headers show
Series [Openvpn-devel,v4] Silence compiler truncation warning by checking snprintf return value | expand

Commit Message

Frank Lichtenheld Jan. 21, 2026, 12:18 p.m. UTC 
From: Arne Schwabe <arne@rfc2549.org>

On the more recent mingw compilers (homebrew mingw 13.0.0, GCC 15.2.0) the
compiler complains about a potential truncation in these two places.

  src/openvpn/tun.c:3806:57:
  error: '%s' directive output may be truncated writing up
  to 255 bytes into a region of size 178
  [-Werror=format-truncation=]

This not very helpful but checking the snprintf return value
will make the compiler not warn about this.

Change-Id: I54b11a5540fb236580a3b80c6d1e8678b24bd852
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1272
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1272
This mail reflects revision 4 of this Change.

Acked-by according to Gerrit (reflected above):
Frank Lichtenheld <frank@lichtenheld.com>

Comments

Gert Doering Jan. 24, 2026, 3:49 p.m. UTC | #1 
Compilers... but yeah, the change won't do harm, and might catch something
unexpected with a proper error message.  Doesn't change the actual code
flow, so not tested beyond "is the compiler fine with it".

Your patch has been applied to the master branch.

commit 1fe958183fa5877d9e00cbfbe0d29477adff7187
Author: Arne Schwabe
Date:   Wed Jan 21 13:18:30 2026 +0100

     Silence compiler truncation warning by checking snprintf return value

     Signed-off-by: Arne Schwabe <arne@rfc2549.org>
     Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
     Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1272
     Message-Id: <20260121121830.27244-1-frank@lichtenheld.com>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg35367.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering
diff mbox series

Patch

diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
index 0399b4a..e38df3e 100644
--- a/src/openvpn/tun.c
+++ b/src/openvpn/tun.c
@@ -3558,7 +3558,13 @@ 
             msg(M_FATAL, "Error enumerating registry subkeys of key: %s", ADAPTER_KEY);
         }
 
-        snprintf(unit_string, sizeof(unit_string), "%s\\%s", ADAPTER_KEY, enum_name);
+        int ret = snprintf(unit_string, sizeof(unit_string), "%s\\%s", ADAPTER_KEY, enum_name);
+
+        if (ret < 0 || ret >= sizeof(unit_string))
+        {
+            msg(M_WARN, "Error constructing unit string for %s", enum_name);
+            continue;
+        }
 
         status = RegOpenKeyEx(HKEY_LOCAL_MACHINE, unit_string, 0, KEY_READ, &unit_key);
 
@@ -3667,8 +3673,15 @@ 
             msg(M_FATAL, "Error enumerating registry subkeys of key: %s", NETWORK_CONNECTIONS_KEY);
         }
 
-        snprintf(connection_string, sizeof(connection_string), "%s\\%s\\Connection",
-                 NETWORK_CONNECTIONS_KEY, enum_name);
+        int ret = snprintf(connection_string, sizeof(connection_string), "%s\\%s\\Connection",
+                           NETWORK_CONNECTIONS_KEY, enum_name);
+
+        if (ret < 0 || ret >= sizeof(connection_string))
+        {
+            msg(M_WARN, "Error constructing connection string for %s", enum_name);
+            continue;
+        }
+
 
         status = RegOpenKeyEx(HKEY_LOCAL_MACHINE, connection_string, 0, KEY_READ, &connection_key);