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[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>
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);