From: Florian Forster <octo@collectd.org>
Date: Thu, 11 Jan 2024 20:44:39 +0000 (+0100)
Subject: common: Reserve a null byte when calling `strncpy`.
X-Git-Tag: 6.0.0-rc0~13^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7de6192d5f827f0204cbf8c45ca921c3ed298cc8;p=thirdparty%2Fcollectd.git

common: Reserve a null byte when calling `strncpy`.

While `sstrncpy` guarantees a null terminated string, some compilers don't get
the memo and complain about the buffer size being equal to the size provided to
*strncpy(3)*. This *is* a potential source of error with *strncpy(3)*, because
if the source string is longer than the buffer, the buffer is not null
terminated. That is the precise reason `sstrncpy` exists in the first place.

Make these compilers happy by decreasing the size passed to *strncpy(3)* by
one.
---

diff --git a/src/utils/common/common.c b/src/utils/common/common.c
index ad72e93ff..31e6146af 100644
--- a/src/utils/common/common.c
+++ b/src/utils/common/common.c
@@ -85,8 +85,10 @@ static pthread_mutex_t strerror_r_lock = PTHREAD_MUTEX_INITIALIZER;
 #endif
 
 char *sstrncpy(char *dest, const char *src, size_t n) {
-  strncpy(dest, src, n);
-  dest[n - 1] = '\0';
+  if (n > 0) {
+    strncpy(dest, src, n - 1);
+    dest[n - 1] = 0;
+  }
 
   return dest;
 } /* char *sstrncpy */