diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 2f6e1f21a920..39e8895aeb1f 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,9 @@
+2018-02-16  Richard Biener  <rguenther@suse.de>
+
+	PR bootstrap/82939
+	* line-map.c (linemap_init): Avoid broken value-init when compiling
+	with GCC 4.2.
+
 2018-02-15  Jason Merrill  <jason@redhat.com>
 	    Jakub Jelinek  <jakub@redhat.com>
 
diff --git a/libcpp/line-map.c b/libcpp/line-map.c
index 677acd6dd925..a84084c99f05 100644
--- a/libcpp/line-map.c
+++ b/libcpp/line-map.c
@@ -344,7 +344,12 @@ void
 linemap_init (struct line_maps *set,
 	      source_location builtin_location)
 {
+#if __GNUC__ == 4 && __GNUC_MINOR__ == 2 && !defined (__clang__)
+  /* PR33916, needed to fix PR82939.  */
+  memset (set, 0, sizeof (struct line_maps));
+#else
   *set = line_maps ();
+#endif
   set->highest_location = RESERVED_LOCATION_COUNT - 1;
   set->highest_line = RESERVED_LOCATION_COUNT - 1;
   set->location_adhoc_data_map.htab =