fix: add STRNLEN compatability macro

Older SunOS systems come without strnlen, add STRNLEN macro in line with
the other str* compat macros.

config/CMakeLists.txt

@@ -45,6 +45,7 @@ check_function_exists(readlink HAVE_READLINK)
 check_function_exists(setpgid HAVE_SETPGID)
 check_function_exists(setsid HAVE_SETSID)
 check_function_exists(sigaction HAVE_SIGACTION)
+check_function_exists(strnlen HAVE_STRNLEN)
 check_function_exists(strcasecmp HAVE_STRCASECMP)
 check_function_exists(strncasecmp HAVE_STRNCASECMP)
 check_function_exists(strptime HAVE_STRPTIME)

config/config.h.in

@@ -30,6 +30,7 @@
 #cmakedefine HAVE_SETPGID
 #cmakedefine HAVE_SETSID
 #cmakedefine HAVE_SIGACTION
+#cmakedefine HAVE_STRNLEN
 #cmakedefine HAVE_STRCASECMP
 #cmakedefine HAVE_STRINGS_H
 #cmakedefine HAVE_STRNCASECMP

src/nvim/api/private/helpers.c

@@ -513,7 +513,7 @@ String cbuf_to_string(const char *buf, size_t size)
 String cstrn_to_string(const char *str, size_t maxsize)
   FUNC_ATTR_NONNULL_ALL
 {
-  return cbuf_to_string(str, strnlen(str, maxsize));
+  return cbuf_to_string(str, STRNLEN(str, maxsize));
 }
 
 /// Creates a String using the given C string. Unlike

src/nvim/message.c

@@ -2056,7 +2056,7 @@ static void msg_puts_display(const char_u *str, int maxlen, int attr, int recurs
       msg_ext_last_attr = attr;
     }
     // Concat pieces with the same highlight
-    size_t len = strnlen((char *)str, maxlen);             // -V781
+    size_t len = STRNLEN(str, maxlen);             // -V781
     ga_concat_len(&msg_ext_last_chunk, (char *)str, len);
     msg_ext_cur_len += len;
     return;

src/nvim/strings.c

@@ -394,6 +394,18 @@ void del_trailing_spaces(char_u *ptr)
   }
 }
 
+#if !defined(HAVE_STRNLEN)
+size_t xstrnlen(const char *s, size_t n)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
+{
+  const char *end = memchr(s, '\0', n);
+  if (end == NULL) {
+    return n;
+  }
+  return end - s;
+}
+#endif
+
 #if (!defined(HAVE_STRCASECMP) && !defined(HAVE_STRICMP))
 /*
  * Compare two strings, ignoring case, using current locale.

src/nvim/vim.h

@@ -215,6 +215,11 @@ enum { FOLD_TEXT_LEN = 51, };  //!< buffer size for get_foldtext()
 // (vim_strchr() is now in strings.c)
 
 #define STRLEN(s)           strlen((char *)(s))
+#ifdef HAVE_STRNLEN
+#  define STRNLEN(s, n)     strnlen((char *)(s), (size_t)(n))
+#else
+#  define STRNLEN(s, n)     xstrnlen((char *)(s), (size_t)(n))
+#endif
 #define STRCPY(d, s)        strcpy((char *)(d), (char *)(s))
 #define STRNCPY(d, s, n)    strncpy((char *)(d), (char *)(s), (size_t)(n))
 #define STRLCPY(d, s, n)    xstrlcpy((char *)(d), (char *)(s), (size_t)(n))