[7/7] gdb: generate dwarf-5 index identically as worker-thread count changes
Checks
| Context |
Check |
Description |
| linaro-tcwg-bot/tcwg_gdb_build--master-aarch64 |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_build--master-arm |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_check--master-arm |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_check--master-aarch64 |
success
|
Testing passed
|
Commit Message
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.
---
gdb/dwarf2/index-write.c | 17 +++++++++++++++--
gdb/testsuite/gdb.gdb/index-file.exp | 8 +++++++-
2 files changed, 22 insertions(+), 3 deletions(-)
@@ -454,6 +454,11 @@ class c_str_view
return strcmp (m_cstr, other.m_cstr) == 0;
}
+ bool operator< (const c_str_view &other) const
+ {
+ return strcmp (m_cstr, other.m_cstr) < 0;
+ }
+
/* Return the underlying C string. Note, the returned string is
only a reference with lifetime of this object. */
const char *c_str () const
@@ -773,10 +778,18 @@ class debug_names
}
for (size_t bucket_ix = 0; bucket_ix < bucket_hash.size (); ++bucket_ix)
{
- const std::forward_list<hash_it_pair> &hashitlist
- = bucket_hash[bucket_ix];
+ std::forward_list<hash_it_pair> &hashitlist = bucket_hash[bucket_ix];
if (hashitlist.empty ())
continue;
+
+ /* Sort the items within each bucket. This ensures that the
+ generated index files will be the same no matter the order in
+ which symbols were added into the index. */
+ hashitlist.sort ([] (const hash_it_pair &a, const hash_it_pair &b)
+ {
+ return a.it->first < b.it->first;
+ });
+
uint32_t &bucket_slot = m_bucket_table[bucket_ix];
/* The hashes array is indexed starting at 1. */
store_unsigned_integer (reinterpret_cast<gdb_byte *> (&bucket_slot),
@@ -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}\""]