diff --git a/incdefs.sh b/incdefs.sh
index cf00eaf..5bbdcea 100755
--- a/incdefs.sh
+++ b/incdefs.sh
@@ -23,12 +23,15 @@
 #
 user_flags()
 {
+	# Needed for vasprintf().
+	printf " -D_GNU_SOURCE"
+
 	dirs=$(echo "" | ${CROSS_COMPILE}cpp -Wp,-v 2>&1 >/dev/null | grep ^" /")
 	for d in $dirs; do
 		files=$(find $d -type f -name time.h)
 		for f in $files; do
 			if grep -q clock_adjtime $f; then
-				printf " -D_GNU_SOURCE -DHAVE_CLOCK_ADJTIME"
+				printf " -DHAVE_CLOCK_ADJTIME"
 				return
 			fi
 		done
diff --git a/util.c b/util.c
index cb428b1..06c3296 100644
--- a/util.c
+++ b/util.c
@@ -18,6 +18,7 @@
  */
 #include <errno.h>
 #include <signal.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -342,3 +343,97 @@ int is_running(void)
 {
 	return running;
 }
+
+char *string_newf(const char *format, ...)
+{
+	va_list ap;
+	char *s;
+
+	va_start(ap, format);
+	if (vasprintf(&s, format, ap) < 0)
+		s = NULL;
+	va_end(ap);
+
+	return s;
+}
+
+void string_append(char **s, const char *str)
+{
+	size_t len1, len2;
+
+	len1 = strlen(*s);
+	len2 = strlen(str);
+	*s = realloc(*s, len1 + len2 + 1);
+	if (*s)
+		memcpy((*s) + len1, str, len2 + 1);
+}
+
+void string_appendf(char **s, const char *format, ...)
+{
+	va_list ap;
+	size_t len1, len2;
+	char *s2;
+
+	len1 = strlen(*s);
+
+	va_start(ap, format);
+	len2 = vasprintf(&s2, format, ap);
+	va_end(ap);
+
+	if (len2 < 0) {
+		*s = NULL;
+		return;
+	}
+
+	*s = realloc(*s, len1 + len2 + 1);
+	if (*s)
+		memcpy((*s) + len1, s2, len2 + 1);
+	free(s2);
+}
+
+void **parray_new(void)
+{
+	void **a = malloc(sizeof(*a));
+
+	if (a)
+		*a = NULL;
+	return a;
+}
+
+void parray_append(void ***a, void *p)
+{
+	parray_extend(a, p, NULL);
+}
+
+void parray_extend(void ***a, ...)
+{
+	va_list ap;
+	int ilen, len, alloced;
+	void *p;
+
+	for (len = 0; (*a)[len]; len++)
+		;
+	len++;
+
+	va_start(ap, a);
+	for (ilen = 0; va_arg(ap, void *); ilen++)
+		;
+	va_end(ap);
+
+	/* Reallocate in exponentially increasing sizes. */
+	for (alloced = 1; alloced < len; alloced <<= 1)
+		;
+	if (alloced < len + ilen) {
+		while (alloced < len + ilen)
+			alloced *= 2;
+		*a = realloc(*a, alloced * sizeof **a);
+		if (!*a)
+			return;
+	}
+
+	va_start(ap, a);
+	while ((p = va_arg(ap, void *)))
+		(*a)[len++ - 1] = p;
+	va_end(ap);
+	(*a)[len - 1] = NULL;
+}
diff --git a/util.h b/util.h
index bb29e11..98b395b 100644
--- a/util.h
+++ b/util.h
@@ -236,4 +236,61 @@ int handle_term_signals(void);
  */
 int is_running(void);
 
+/**
+ * Get an allocated and formatted string. This is a wrapper around asprintf().
+ *
+ * @param format    printf() format string.
+ * @param ...       printf() arguments.
+ * @return          Pointer to the allocated string, NULL on error.
+ */
+#ifdef __GNUC__
+__attribute__ ((format (printf, 1, 2)))
+#endif
+char *string_newf(const char *format, ...);
+
+/**
+ * Reallocate a string and append another string to it.
+ *
+ * @param s         String that should be extended, set to NULL on error.
+ * @param str       String appended to s.
+ */
+void string_append(char **s, const char *str);
+#ifdef __GNUC__
+__attribute__ ((format (printf, 2, 3)))
+#endif
+/**
+ * Reallocate a string and append a formatted string to it.
+ *
+ * @param s         String that should be extended, set to NULL on error.
+ * @param format    printf() format string.
+ * @param ...       printf() arguments.
+ */
+void string_appendf(char **s, const char *format, ...);
+
+/**
+ * Get an empty array of pointers terminated by NULL.
+ *
+ * @return          Pointer to the allocated array, NULL on error.
+ */
+void **parray_new(void);
+
+/**
+ * Append pointer to a NULL-terminated pointer array. The array is reallocated
+ * in exponentially increasing sizes.
+ *
+ * @param a         Pointer to pointer array, set to NULL on error.
+ * @param p         Pointer appended to the array.
+ */
+void parray_append(void ***a, void *p);
+
+
+/**
+ * Append pointers to a NULL-terminated pointer array. The array is reallocated
+ * in exponentially increasing sizes.
+ *
+ * @param a         Pointer to pointer array, set to NULL on error.
+ * @param ...       NULL-terminated list of pointers.
+ */
+void parray_extend(void ***a, ...);
+
 #endif