gdb: generate dwarf-5 index identically as worker-thread count changes

Similar to the previous commit, this commit ensures that the dwarf-5
index files are generated identically as the number of worker-threads
changes.

Building the dwarf-5 index makes use of a closed hash table, the
bucket_hash local within debug_names::build().  Entries are added to
bucket_hash from m_name_to_value_set, which, in turn, is populated
by calls to debug_names::insert() in write_debug_names.  The insert
calls are ordered based on the entries within the cooked_index, and
the ordering within cooked_index depends on the number of worker
threads that GDB is using.

My proposal is to sort each chain within the bucket_hash closed hash
table prior to using this to build the dwarf-5 index.

The buckets within bucket_hash will always have the same ordering (for
a given GDB build with a given executable), and by sorting the chains
within each bucket, we can be sure that GDB will see each entry in a
deterministic order.

I've extended the index creation test to cover this case.

Approved-By: Tom Tromey <tom@tromey.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/gdb/testsuite/gdb.gdb/index-file.exp b/gdb/testsuite/gdb.gdb/index-file.exp
index 0841592..7154d23 100644
--- a/gdb/testsuite/gdb.gdb/index-file.exp
+++ b/gdb/testsuite/gdb.gdb/index-file.exp
@@ -44,6 +44,9 @@ remote_exec host "mkdir -p ${dir1}"
 with_timeout_factor $timeout_factor {
     gdb_test_no_output "save gdb-index $dir1" \
 	"create gdb-index file"
+
+    gdb_test_no_output "save gdb-index -dwarf-5 $dir1" \
+	"create dwarf-index files"
 }
 
 # Close GDB.
@@ -140,13 +143,16 @@ if { $worker_threads > 1 } {
     with_timeout_factor $timeout_factor {
 	gdb_test_no_output "save gdb-index $dir2" \
 	    "create second gdb-index file"
+
+	gdb_test_no_output "save gdb-index -dwarf-5 $dir2" \
+	    "create second dwarf-index files"
     }
 
     # Close GDB.
     gdb_exit
 
     # Now check that the index files are identical.
-    foreach suffix { gdb-index  } {
+    foreach suffix { gdb-index debug_names debug_str } {
 	set result \
 	    [remote_exec host \
 		 "cmp -s \"$dir1/${index_filename_base}.${suffix}\" \"$dir2/${index_filename_base}.${suffix}\""]