diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c399bc1..4c6674a 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -565,6 +565,10 @@
  * @fmt: The format string to use
  * @args: Arguments for the format string
  *
+ * This function follows C99 vsnprintf, but has some extensions:
+ * %pS output the name of a text symbol
+ * %pF output the name of a function pointer
+ *
  * The return value is the number of characters which would
  * be generated for the given input, excluding the trailing
  * '\0', as per ISO C99. If you want to have the exact
@@ -806,6 +810,8 @@
  *
  * Call this function if you are already dealing with a va_list.
  * You probably want scnprintf() instead.
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
  */
 int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
 {
@@ -828,6 +834,8 @@
  * generated for the given input, excluding the trailing null,
  * as per ISO C99.  If the return is greater than or equal to
  * @size, the resulting string is truncated.
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
  */
 int snprintf(char * buf, size_t size, const char *fmt, ...)
 {
@@ -877,6 +885,8 @@
  *
  * Call this function if you are already dealing with a va_list.
  * You probably want sprintf() instead.
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
  */
 int vsprintf(char *buf, const char *fmt, va_list args)
 {
@@ -894,6 +904,8 @@
  * The function returns the number of characters written
  * into @buf. Use snprintf() or scnprintf() in order to avoid
  * buffer overflows.
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
  */
 int sprintf(char * buf, const char *fmt, ...)
 {