Fix clang compile errors

2 files changed, 23 insertions, 10 deletions

diff --git a/src/util/string.c b/src/util/string.c
index c760b06..b17823e 100644
--- a/src/util/string.c
+++ b/src/util/string.c
@@ -68,6 +68,8 @@ size_t _vstrjoin_r(char *restrict buf, size_t buflen, char sep, va_list ap) {
 	const char *s;
 	size_t len = 0;
 
+	buflen /= sizeof(*buf);  /* convert buflen to an "array length limit" */
+
 	if (NULL != buf && 0 < buflen) {
 		/* clear buf string */
 		*buf = '\0';
@@ -82,37 +84,48 @@ size_t _vstrjoin_r(char *restrict buf, size_t buflen, char sep, va_list ap) {
 			++len;
 		}
 
-		if (NULL != buf) {
+		if (NULL != buf && 0 < (buflen - len)) {
 			/* append element */
 			strncpy(buf+len, s, (buflen - len));
 		}
 		len += strlen(s);
 	}
 
+	if (NULL != buf && 0 < buflen) *(buf + buflen-1) = '\0';
+
 	return len;
 }
 
 size_t _strjoin_r(
-		char *restrict buf, size_t buflen, char sep, /* const char *restrict */...) {
+		char sep, char *restrict buf, size_t buflen, /* const char *restrict */...) {
 	va_list ap;
-	va_start(ap, sep);
+	va_start(ap, buflen);
 	size_t len = _vstrjoin_r(buf, buflen, sep, ap);
 	va_end(ap);
 	return len;
 }
 
-char *_strjoin(char sep, /* const char *restrict */...) {
+/** NOTE: the _ argument is added to "hack" around undefined behaviour if the 
+ *        last non-variadic argument undergoes argument promotion.
+ *        This results in a compile error on (at least) clang:
+ *
+ * src/util/string.c:130:16: error: passing an object that undergoes default 
+ * argument promotion to 'va_start' has undefined behavior [-Werror,-Wvarargs] 
+ */
+char *_strjoin(char sep, void *_, /* const char *restrict */...) {
 	va_list ap;
 
 	/* determine length of result string */
-	va_start(ap, sep);
+	va_start(ap, _);
 	size_t len = _vstrjoin_r(NULL, 0, sep, ap);
 	va_end(ap);
 
 	/* allocate destination buffer */
 	char *dest = malloc(len+1);
 	if (NULL != dest) {
+		va_start(ap, _);
 		(void)_vstrjoin_r(dest, len+1, sep, ap);
+		va_end(ap);
 	}
 
 	return dest;
diff --git a/src/util/string.h b/src/util/string.h
index b75e783..5e31e21 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -132,9 +132,9 @@ size_t stranjoin_r(
 
 
 char *_strjoin(  /* internal */
-	char sep, /* const char * */...);
+	char sep, void *_, /* const char * */...);
 size_t _strjoin_r(  /* internal */
-	char *restrict buf, size_t buflen, char sep, /* const char * */...);
+	char sep, char *restrict buf, size_t buflen, /* const char * */...);
 
 /**
  * strjoin:
@@ -146,20 +146,20 @@ size_t _strjoin_r(  /* internal */
  * @param ...: a list of strings to join
  * @return a newly-allocated string containing all of the strings joined
  */
-#define strjoin(sep, ...) _strjoin(sep, __VA_ARGS__, NULL)
+#define strjoin(sep, ...) _strjoin(sep, NULL, __VA_ARGS__, NULL)
 
 /**
  * strjoin_r:
  * Joins a number of strings together to form one long string stored in a
  * caller-allocated buffer with the @separator inserted betwween each of them.
  *
+ * @param sep: a char to insert between each of the strings
  * @param buf: the destination buffer (nothing will be written to it if NULL)
  * @param buflen: the length of @buf
- * @param sep: a char to insert between each of the strings
  * @param ...: a list of strings to join
  * @return the length of the untruncated joined string
  */
-#define strjoin_r(sep, ...) _strjoin_r(sep, __VA_ARGS__, NULL)
+#define strjoin_r(buf, buflen, sep, ...) _strjoin_r(sep, buf, buflen, __VA_ARGS__, NULL)
 
 /**
  * pathjoin: