gcov-tool: Allow merging of empty profile lists

The gcov_profile_merge() already had code to deal with profile information
which had no counterpart to merge with.  For profile information from files
with no associated counterpart, the profile information is simply used as is
with the weighting transformation applied.  Make sure that gcov_profile_merge()
works with an empty target profile list.  Return the merged profile list.

gcc/
	* gcov-tool.cc (gcov_profile_merge): Adjust return type.
	(profile_merge): Allow merging of directories which contain no profile
	files.

libgcc/
	* libgcov-util.c (gcov_profile_merge): Return the list of merged
	profiles.  Accept empty target and source profile lists.

1 files changed, 11 insertions, 8 deletions

diff --git a/libgcc/libgcov-util.c b/libgcc/libgcov-util.c
index ba7fb92..100f1b1 100644
--- a/libgcc/libgcov-util.c
+++ b/libgcc/libgcov-util.c
@@ -674,16 +674,16 @@ find_match_gcov_info (struct gcov_info **array, int size,
 }
 
 /* Merge the list of gcov_info objects from SRC_PROFILE to TGT_PROFILE.
-   Return 0 on success: without mismatch.
-   Reutrn 1 on error.  */
+   Return the list of merged gcov_info objects.  Return NULL if the list is
+   empty.  */
 
-int
+struct gcov_info *
 gcov_profile_merge (struct gcov_info *tgt_profile, struct gcov_info *src_profile,
                     int w1, int w2)
 {
   struct gcov_info *gi_ptr;
   struct gcov_info **tgt_infos;
-  struct gcov_info *tgt_tail;
+  struct gcov_info **tgt_tail;
   struct gcov_info **in_src_not_tgt;
   unsigned tgt_cnt = 0, src_cnt = 0;
   unsigned unmatch_info_cnt = 0;
@@ -703,7 +703,10 @@ gcov_profile_merge (struct gcov_info *tgt_profile, struct gcov_info *src_profile
   for (gi_ptr = tgt_profile, i = 0; gi_ptr; gi_ptr = gi_ptr->next, i++)
     tgt_infos[i] = gi_ptr;
 
-  tgt_tail = tgt_infos[tgt_cnt - 1];
+  if (tgt_cnt)
+     tgt_tail = &tgt_infos[tgt_cnt - 1]->next;
+  else
+     tgt_tail = &tgt_profile;
 
   /* First pass on tgt_profile, we multiply w1 to all counters.  */
   if (w1 > 1)
@@ -732,14 +735,14 @@ gcov_profile_merge (struct gcov_info *tgt_profile, struct gcov_info *src_profile
       gi_ptr = in_src_not_tgt[i];
       gcov_merge (gi_ptr, gi_ptr, w2 - 1);
       gi_ptr->next = NULL;
-      tgt_tail->next = gi_ptr;
-      tgt_tail = gi_ptr;
+      *tgt_tail = gi_ptr;
+      tgt_tail = &gi_ptr->next;
     }
 
   free (in_src_not_tgt);
   free (tgt_infos);
 
-  return 0;
+  return tgt_profile;
 }
 
 typedef gcov_type (*counter_op_fn) (gcov_type, void*, void*);