gdb/dwarf: pass dwarf2_per_bfd to dwarf2_per_cu_data constructor

Pass a dwarf2_per_bfd to the constructor of dwarf2_per_cu_data and set
the per_bfd field there.  All "real" instantiations of
dwarf2_per_cu_data must have a valid, non-nullptr dwarf2_per_bfd
backlink, this makes it a bit more obvious.  The instantiations of
dwarf2_per_cu_data that receive a nullptr dwarf2_per_bfd are the ones
used to do hash map lookups and the ones used in selftests.

Remove an unnecessary assignment of per_bfd in
fill_in_sig_entry_from_dwo_entry: the per_bfd field is already set when
the signatured_type object is constructor (before that, it was set in
allocate_signatured_type).

Change-Id: Ifeebe55fdb1bc2de4de9c852033fafe8abdfde8a
Approved-By: Tom Tromey <tom@tromey.com>

2 files changed, 18 insertions, 20 deletions

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 9fdd1cd..0d4bfff 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1818,8 +1818,7 @@ dw2_instantiate_symtab (dwarf2_per_cu_data *per_cu,
 dwarf2_per_cu_data_up
 dwarf2_per_bfd::allocate_per_cu ()
 {
-  dwarf2_per_cu_data_up result (new dwarf2_per_cu_data);
-  result->per_bfd = this;
+  dwarf2_per_cu_data_up result (new dwarf2_per_cu_data (this));
   result->index = all_units.size ();
   return result;
 }
@@ -1829,8 +1828,7 @@ dwarf2_per_bfd::allocate_per_cu ()
 signatured_type_up
 dwarf2_per_bfd::allocate_signatured_type (ULONGEST signature)
 {
-  signatured_type_up result (new signatured_type (signature));
-  result->per_bfd = this;
+  signatured_type_up result (new signatured_type (this, signature));
   result->index = all_units.size ();
   result->is_debug_types = true;
   tu_stats.nr_tus++;
@@ -2766,7 +2764,6 @@ fill_in_sig_entry_from_dwo_entry (dwarf2_per_objfile *per_objfile,
   sig_entry->sect_off = dwo_entry->sect_off;
   sig_entry->set_length (dwo_entry->length, false);
   sig_entry->reading_dwo_directly = 1;
-  sig_entry->per_bfd = per_bfd;
   sig_entry->type_offset_in_tu = dwo_entry->type_offset_in_tu;
   sig_entry->dwo_unit = dwo_entry;
 }
@@ -2805,7 +2802,7 @@ lookup_dwo_signatured_type (struct dwarf2_cu *cu, ULONGEST sig)
      the TU has an entry in .gdb_index, replace the recorded data from
      .gdb_index with this TU.  */
 
-  signatured_type find_sig_entry (sig);
+  signatured_type find_sig_entry (nullptr, sig);
   slot = htab_find_slot (per_bfd->signatured_types.get (), &find_sig_entry,
 			 INSERT);
   signatured_type *sig_entry = (struct signatured_type *) *slot;
@@ -2867,7 +2864,7 @@ lookup_dwp_signatured_type (struct dwarf2_cu *cu, ULONGEST sig)
   if (per_bfd->signatured_types == NULL)
     per_bfd->signatured_types = allocate_signatured_type_table ();
 
-  signatured_type find_sig_entry (sig);
+  signatured_type find_sig_entry (nullptr, sig);
   slot = htab_find_slot (per_bfd->signatured_types.get (), &find_sig_entry,
 			 INSERT);
   signatured_type *sig_entry = (struct signatured_type *) *slot;
@@ -2913,7 +2910,7 @@ lookup_signatured_type (struct dwarf2_cu *cu, ULONGEST sig)
     {
       if (per_objfile->per_bfd->signatured_types == NULL)
 	return NULL;
-      signatured_type find_entry (sig);
+      signatured_type find_entry (nullptr, sig);
       return ((struct signatured_type *)
 	      htab_find (per_objfile->per_bfd->signatured_types.get (),
 			 &find_entry));
@@ -4052,7 +4049,7 @@ process_skeletonless_type_unit (void **slot, void *info)
   if (per_bfd->signatured_types == NULL)
     per_bfd->signatured_types = allocate_signatured_type_table ();
 
-  signatured_type find_entry (dwo_unit->signature);
+  signatured_type find_entry (nullptr, dwo_unit->signature);
   slot = htab_find_slot (per_bfd->signatured_types.get (), &find_entry, INSERT);
 
   /* If we've already seen this type there's nothing to do.  What's happening
@@ -7142,13 +7139,12 @@ create_cus_hash_table (dwarf2_per_objfile *per_objfile,
   end_ptr = info_ptr + section.size;
   while (info_ptr < end_ptr)
     {
-      struct dwarf2_per_cu_data per_cu;
       struct dwo_unit read_unit {};
       struct dwo_unit *dwo_unit;
       void **slot;
       sect_offset sect_off = (sect_offset) (info_ptr - section.buffer);
 
-      per_cu.per_bfd = per_bfd;
+      dwarf2_per_cu_data per_cu (per_bfd);
       per_cu.is_debug_types = 0;
       per_cu.sect_off = sect_offset (info_ptr - section.buffer);
       per_cu.section = &section;
@@ -21146,13 +21142,13 @@ namespace find_containing_comp_unit {
 static void
 run_test ()
 {
-  dwarf2_per_cu_data_up one (new dwarf2_per_cu_data);
+  dwarf2_per_cu_data_up one (new dwarf2_per_cu_data (nullptr));
   dwarf2_per_cu_data *one_ptr = one.get ();
-  dwarf2_per_cu_data_up two (new dwarf2_per_cu_data);
+  dwarf2_per_cu_data_up two (new dwarf2_per_cu_data (nullptr));
   dwarf2_per_cu_data *two_ptr = two.get ();
-  dwarf2_per_cu_data_up three (new dwarf2_per_cu_data);
+  dwarf2_per_cu_data_up three (new dwarf2_per_cu_data (nullptr));
   dwarf2_per_cu_data *three_ptr = three.get ();
-  dwarf2_per_cu_data_up four (new dwarf2_per_cu_data);
+  dwarf2_per_cu_data_up four (new dwarf2_per_cu_data (nullptr));
   dwarf2_per_cu_data *four_ptr = four.get ();
 
   one->set_length (5);
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 23cb506..b2cf9be 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -96,7 +96,7 @@ using dwarf2_per_cu_data_up
 
 struct dwarf2_per_cu_data
 {
-  dwarf2_per_cu_data ()
+  dwarf2_per_cu_data (dwarf2_per_bfd *per_bfd)
     : is_debug_types (false),
       is_dwz (false),
       reading_dwo_directly (false),
@@ -106,7 +106,8 @@ struct dwarf2_per_cu_data
       m_header_read_in (false),
       mark (false),
       files_read (false),
-      scanned (false)
+      scanned (false),
+      per_bfd (per_bfd)
   {
   }
 
@@ -209,7 +210,7 @@ public:
   struct dwarf2_section_info *section = nullptr;
 
   /* Backlink to the owner of this.  */
-  dwarf2_per_bfd *per_bfd = nullptr;
+  dwarf2_per_bfd *per_bfd;
 
   /* DWARF header of this CU.  Note that dwarf2_cu reads its own version of the
      header, which may differ from this one, since it may pass rcuh_kind::TYPE
@@ -367,8 +368,9 @@ public:
 
 struct signatured_type : public dwarf2_per_cu_data
 {
-  signatured_type (ULONGEST signature)
-    : signature (signature)
+  signatured_type (dwarf2_per_bfd *per_bfd, ULONGEST signature)
+    : dwarf2_per_cu_data (per_bfd),
+      signature (signature)
   {}
 
   /* The type's signature.  */