tweak get_source_text_between comment
diff --git a/gcc/input.cc b/gcc/input.cc
index 04d0809..c185bd7 100644
--- a/gcc/input.cc
+++ b/gcc/input.cc
@@ -949,8 +949,9 @@
return char_span (buffer, len);
}
-/* Return a copy of the source text between two locations. The caller is
- responsible for freeing the return value. */
+/* Return a NUL-terminated copy of the source text between two locations, or
+ NULL if the arguments are invalid. The caller is responsible for freeing
+ the return value. */
char *
get_source_text_between (location_t start, location_t end)
