dwarf-reader: get_die_source: always initialize return value

GCC9 with ABIGAIL_DEVEL=1 and ABIGAIL_DEBUG=1 set, regularly emits
-Werror=maybe-uninitialized for the values gathered by get_die_source.
As a counter measure, some of them were initialized before the call to
NO_DEBUG_INFO_DIE_SOURCE, but not all of them, leading to said warning.
In order to overcome this, let get_die_source always initialize the
source to NO_DEBUG_INFO_DIE_SOURCE and adjust the caller to consistently
not do that anymore. This solves the warning and maybe but unlikely (due
to the ABG_ASSERT) avoids some UB.

Changing the interface of get_die_source to return the source directly,
lead to the ability to initialize the value const and to defer the
assertion to the function itself. Some occurrences could be removed
entirely as the die_source was not used at all.

	* src/abg-dwarf-reader.cc
	(read_context::get_die_source): Always initialize die_source.
	(read_context::ContainerType::get_container): Fix
	initialization of die_source.
	(read_context::compute_canonical_die): Likewise.
	(read_context::get_canonical_die): Likewise.
	(read_context::get_or_compute_canonical_die): Likewise.
	(read_context::associate_die_to_decl): Likewise.
	(read_context::set_canonical_die_offset): Likewise.
	(read_context::schedule_type_for_late_canonicalization): Likewise.
	(read_context::compare_dies): Likewise.
	(read_context::get_parent_die): Likewise.
	(read_context::get_scope_for_die): Likewise.
	(read_context::add_or_update_union_type): Likewise.
	(read_context::maybe_canonicalize_type): Likewise.
	(read_context::build_ir_node_from_die): Likewise.

Signed-off-by: Matthias Maennich <maennich@google.com>

diff --git a/src/abg-dwarf-reader.cc b/src/abg-dwarf-reader.cc
index 05130730d5ec9a0f0f40ab8da38ccab12cf7c702..213638102230f83b9d1903ec7c9db614bd8c3797 100644 (file)
--- a/src/abg-dwarf-reader.cc
+++ b/src/abg-dwarf-reader.cc
@@ -2106,8 +2106,7 @@ public:
     ContainerType&
     get_container(const read_context& ctxt, const Dwarf_Die *die)
     {
-      die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-      ABG_ASSERT(ctxt.get_die_source(die, source));
+      const die_source source = ctxt.get_die_source(die);
       return get_container(source);
     }
 
@@ -2891,9 +2890,7 @@ public:
                        Dwarf_Die &canonical_die,
                        bool die_as_type) const
   {
-    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-
-    ABG_ASSERT(get_die_source(die, source));
+    const die_source source = get_die_source(die);
 
     Dwarf_Off die_offset = dwarf_dieoffset(const_cast<Dwarf_Die*>(die));
 
@@ -3021,8 +3018,7 @@ public:
                    size_t where,
                    bool die_as_type) const
   {
-    die_source source;
-    ABG_ASSERT(get_die_source(die, source));
+    const die_source source = get_die_source(die);
 
     offset_offset_map_type &canonical_dies =
       die_as_type
@@ -3130,8 +3126,7 @@ public:
                               size_t where,
                               bool die_as_type) const
   {
-    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-    ABG_ASSERT(get_die_source(die, source));
+    const die_source source = get_die_source(die);
 
     offset_offset_map_type &canonical_dies =
       die_as_type
@@ -3240,16 +3235,15 @@ public:
   ///
   /// @param die the DIE to get the source of.
   ///
-  /// @param source out parameter.  The function sets this parameter
-  /// to the source of the DIE @p iff it returns true.
-  ///
-  /// @return true iff the source of the DIE could be determined and
-  /// returned.
-  bool
-  get_die_source(const Dwarf_Die *die, die_source &source) const
+  /// @return the source of the DIE if it could be determined,
+  /// NO_DEBUG_INFO_DIE_SOURCE otherwise.
+  die_source
+  get_die_source(const Dwarf_Die *die) const
   {
+    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
     ABG_ASSERT(die);
-    return get_die_source(*die, source);
+    ABG_ASSERT(get_die_source(*die, source));
+    return source;
   }
 
   /// Get the source of the DIE.
@@ -3353,8 +3347,7 @@ public:
                        size_t where_offset,
                        bool do_associate_by_repr = false)
   {
-    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-    ABG_ASSERT(get_die_source(die, source));
+    const die_source source = get_die_source(die);
 
     die_artefact_map_type& m =
       decl_die_artefact_maps().get_container(source);
@@ -3981,8 +3974,7 @@ public:
                           Dwarf_Off canonical_die_offset,
                           bool die_as_type) const
   {
-    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-    ABG_ASSERT(get_die_source(die, source));
+    const die_source source = get_die_source(die);
 
     Dwarf_Off die_offset = dwarf_dieoffset(const_cast<Dwarf_Die*>(die));
 
@@ -4562,14 +4554,13 @@ public:
   schedule_type_for_late_canonicalization(const Dwarf_Die *die)
   {
     Dwarf_Off o;
-    die_source source = NO_DEBUG_INFO_DIE_SOURCE;
 
     Dwarf_Die equiv_die;
     ABG_ASSERT(get_canonical_die(die, equiv_die,
                                  /*where=*/0,
                                 /*die_as_type=*/true));
 
-    ABG_ASSERT(get_die_source(&equiv_die, source));
+    const die_source source = get_die_source(&equiv_die);
     o = dwarf_dieoffset(&equiv_die);
 
     const die_artefact_map_type& m =
@@ -11397,10 +11388,8 @@ compare_dies(const read_context& ctxt,
   Dwarf_Off l_offset = dwarf_dieoffset(const_cast<Dwarf_Die*>(l)),
     r_offset = dwarf_dieoffset(const_cast<Dwarf_Die*>(r));
   Dwarf_Off l_canonical_die_offset = 0, r_canonical_die_offset = 0;
-  die_source l_die_source = NO_DEBUG_INFO_DIE_SOURCE,
-    r_die_source = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(l, l_die_source));
-  ABG_ASSERT(ctxt.get_die_source(r, r_die_source));
+  const die_source l_die_source = ctxt.get_die_source(l);
+  const die_source r_die_source = ctxt.get_die_source(r);
 
   // If 'l' and 'r' already have canonical DIEs, then just compare the
   // offsets of their canonical DIEs.
@@ -11847,10 +11836,9 @@ compare_dies(const read_context& ctxt,
       //
       // In case 'r' has no canonical DIE, then compute it, and then
       // propagate that canonical DIE to 'r'.
-      die_source l_source = NO_DEBUG_INFO_DIE_SOURCE,
-       r_source = NO_DEBUG_INFO_DIE_SOURCE;
-      ABG_ASSERT(ctxt.get_die_source(l, l_source));
-      ABG_ASSERT(ctxt.get_die_source(r, r_source));
+      const die_source l_source = ctxt.get_die_source(l);
+      const die_source r_source = ctxt.get_die_source(r);
+
       if (!l_has_canonical_die_offset
          // A DIE can be equivalent only to another DIE of the same
          // source.
@@ -12102,8 +12090,7 @@ get_parent_die(const read_context&      ctxt,
 {
   ABG_ASSERT(ctxt.dwarf());
 
-  die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
+  const die_source source = ctxt.get_die_source(die);
 
   const offset_offset_map_type& m = ctxt.die_parent_map(source);
   offset_offset_map_type::const_iterator i =
@@ -12238,8 +12225,7 @@ get_scope_for_die(read_context& ctxt,
                  bool          called_for_public_decl,
                  size_t        where_offset)
 {
-  die_source source_of_die = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(die, source_of_die));
+  const die_source source_of_die = ctxt.get_die_source(die);
 
   if (is_c_language(ctxt.cur_transl_unit()->get_language()))
     {
@@ -12695,9 +12681,6 @@ build_namespace_decl_and_add_to_ir(read_context&        ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
   if (tag != DW_TAG_namespace && tag != DW_TAG_module)
     return result;
@@ -13308,8 +13291,7 @@ add_or_update_class_type(read_context&   ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
+  const die_source source = ctxt.get_die_source(die);
 
   unsigned tag = dwarf_tag(die);
 
@@ -13686,8 +13668,7 @@ add_or_update_union_type(read_context&  ctxt,
   if (tag != DW_TAG_union_type)
     return result;
 
-  die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
+  const die_source source = ctxt.get_die_source(die);
   {
     die_class_or_union_map_type::const_iterator i =
       ctxt.die_wip_classes_map(source).find(dwarf_dieoffset(die));
@@ -13912,9 +13893,6 @@ build_qualified_type(read_context&      ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
 
   if (tag != DW_TAG_const_type
@@ -14090,9 +14068,6 @@ build_pointer_type_def(read_context&    ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
   if (tag != DW_TAG_pointer_type)
     return result;
@@ -14174,9 +14149,6 @@ build_reference_type(read_context&      ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
   if (tag != DW_TAG_reference_type
       && tag != DW_TAG_rvalue_reference_type)
@@ -14258,8 +14230,7 @@ build_function_type(read_context&       ctxt,
   ABG_ASSERT(dwarf_tag(die) == DW_TAG_subroutine_type
             || dwarf_tag(die) == DW_TAG_subprogram);
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
+  const die_source source = ctxt.get_die_source(die);
 
   decl_base_sptr type_decl;
 
@@ -14462,9 +14433,6 @@ build_subrange_type(read_context&       ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(const_cast<Dwarf_Die*>(die));
   if (tag != DW_TAG_subrange_type)
     return result;
@@ -14639,9 +14607,6 @@ build_array_type(read_context&  ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
   if (tag != DW_TAG_array_type)
     return result;
@@ -14704,9 +14669,6 @@ build_typedef_type(read_context&        ctxt,
   if (!die)
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   unsigned tag = dwarf_tag(die);
   if (tag != DW_TAG_typedef)
     return result;
@@ -14875,9 +14837,6 @@ build_var_decl(read_context&    ctxt,
   if (!die_is_public_decl(die))
     return result;
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   type_base_sptr type;
   Dwarf_Die type_die;
   if (die_die_attribute(die, DW_AT_type, type_die))
@@ -15311,9 +15270,6 @@ build_function_decl(read_context&       ctxt,
     return result;
   ABG_ASSERT(dwarf_tag(die) == DW_TAG_subprogram);
 
-  die_source source;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
-
   if (!die_is_public_decl(die))
     return result;
 
@@ -15777,8 +15733,7 @@ read_debug_info_into_corpus(read_context& ctxt)
 static void
 maybe_canonicalize_type(const Dwarf_Die *die, read_context& ctxt)
 {
-  die_source source = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(die, source));
+  const die_source source = ctxt.get_die_source(die);
 
   size_t die_offset = dwarf_dieoffset(const_cast<Dwarf_Die*>(die));
   type_base_sptr t = ctxt.lookup_type_from_die(die);
@@ -15990,8 +15945,7 @@ build_ir_node_from_die(read_context&    ctxt,
        return result;
     }
 
-  die_source source_of_die = NO_DEBUG_INFO_DIE_SOURCE;
-  ABG_ASSERT(ctxt.get_die_source(die, source_of_die));
+  const die_source source_of_die = ctxt.get_die_source(die);
 
   if ((result = ctxt.lookup_decl_from_die_offset(dwarf_dieoffset(die),
                                                 source_of_die)))