Hi,
this patch implements warning when we merge two virtual tables that do not
match. It compares the size and also go into fields. I had to implement my
own comparsion code, since the vtables may subtly differ - in RTTI and also I
need to do so during DECL merging (since we will forget about the decl then)
Here is an example of real ODR violation in bugzilla it finds.
../../dist/include/mozilla/a11y/DocAccessible.h:40:0: warning: type �struct
DocAccessible� violates one definition rule [enabled by default]
class DocAccessible : public HyperTextAccessibleWrap,
^
/aux/hubicka/firefox/accessible/src/generic/DocAccessible.h:40:0: note: a type
with the same name but different virtual table is defined in another
translation unit
class DocAccessible : public HyperTextAccessibleWrap,
^
/aux/hubicka/firefox/accessible/src/generic/DocAccessible.cpp:1232:0: note: the
first different method is �HandleAccEvent�
DocAccessible::HandleAccEvent(AccEvent* aEvent)
^
/aux/hubicka/firefox/accessible/src/atk/AccessibleWrap.cpp:956:0: note: a
conflicting method is �HandleAccEvent�
AccessibleWrap::HandleAccEvent(AccEvent* aEvent)
^
The patch is not terribly pretty, but does the job. I will wait for few
days for comments/suggestins and then plan to commit it.
PR lto/59468
* lto/lto-symtab.c (lto_symtab_prevailing_decl): Check
virtual tables for ODR violations.
* ipa-devirt.c (compare_virtual_tables): New function.
* ipa-utils.h (compare_virtual_tables): Declare.
Index: lto/lto-symtab.c
===================================================================
--- lto/lto-symtab.c (revision 207702)
+++ lto/lto-symtab.c (working copy)
@@ -679,5 +679,13 @@ lto_symtab_prevailing_decl (tree decl)
if (!ret)
return decl;
+ /* Check and report ODR violations on virtual tables. */
+ if (decl != ret->decl && DECL_VIRTUAL_P (decl))
+ {
+ compare_virtual_tables (ret->decl, decl);
+ /* We are done with checking and DECL will die after merigng. */
+ DECL_VIRTUAL_P (decl) = 0;
+ }
+
return ret->decl;
}
Index: ipa-devirt.c
===================================================================
--- ipa-devirt.c (revision 207702)
+++ ipa-devirt.c (working copy)
@@ -1675,6 +1673,101 @@ update_type_inheritance_graph (void)
}
+/* Compare two virtual tables, PREVAILING and VTABLE and output ODR
+ violation warings. */
+
+void
+compare_virtual_tables (tree prevailing, tree vtable)
+{
+ tree init1 = DECL_INITIAL (prevailing), init2 = DECL_INITIAL (vtable);
+ if (init1 == init2)
+ return;
+ if (init2 == error_mark_node)
+ return;
+ /* Be sure to keep virtual table contents even for external
+ vtables when they are available. */
+ if (init1 == error_mark_node || !init1)
+ {
+ DECL_INITIAL (prevailing) = DECL_INITIAL (vtable);
+ return;
+ }
+ if (!init2 && DECL_EXTERNAL (vtable))
+ return;
+ if (DECL_VIRTUAL_P (prevailing) && init1 && init2
+ && CONSTRUCTOR_NELTS (init1) == CONSTRUCTOR_NELTS (init2))
+ {
+ unsigned i;
+ tree field1, field2;
+ tree val1, val2;
+ bool matched = true;
+
+ FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (init1),
+ i, field1, val1)
+ {
+ gcc_assert (!field1);
+ field2 = CONSTRUCTOR_ELT (init2, i)->index;
+ val2 = CONSTRUCTOR_ELT (init2, i)->value;
+ gcc_assert (!field2);
+ if (val2 == val1)
+ continue;
+ STRIP_NOPS (val1);
+ STRIP_NOPS (val2);
+ /* Unwind
+ val <addr_expr type <pointer_type>
+ readonly constant
+ arg 0 <mem_ref type <pointer_type __vtbl_ptr_type>
+ readonly
+ arg 0 <addr_expr type <pointer_type>
+ arg 0 <var_decl _ZTCSd0_Si>> arg 1 <integer_cst 24>>> */
+
+ while ((TREE_CODE (val1) == MEM_REF
+ && TREE_CODE (val2) == MEM_REF
+ && (TREE_OPERAND (val1, 1)
+ == TREE_OPERAND (val2, 1)))
+ || (TREE_CODE (val1) == ADDR_EXPR
+ && TREE_CODE (val2) == ADDR_EXPR))
+ {
+ val1 = TREE_OPERAND (val1, 0);
+ val2 = TREE_OPERAND (val2, 0);
+ }
+ if (val1 == val2)
+ continue;
+ if (TREE_CODE (val2) == ADDR_EXPR)
+ {
+ tree tmp = val1;
+ val1 = val2;
+ val2 = tmp;
+ }
+ /* Allow combining RTTI and non-RTTI is OK. */
+ if (TREE_CODE (val1) == ADDR_EXPR
+ && TREE_CODE (TREE_OPERAND (val1, 0)) == VAR_DECL
+ && !DECL_VIRTUAL_P (TREE_OPERAND (val1, 0))
+ && TREE_CODE (val2) == NOP_EXPR
+ && integer_zerop (TREE_OPERAND (val2, 0)))
+ continue;
+ if (TREE_CODE (val1) == NOP_EXPR
+ && TREE_CODE (val2) == NOP_EXPR
+ && integer_zerop (TREE_OPERAND (val1, 0))
+ && integer_zerop (TREE_OPERAND (val2, 0)))
+ continue;
+ if (DECL_P (val1) && DECL_P (val2)
+ && DECL_ASSEMBLER_NAME (val1) == DECL_ASSEMBLER_NAME (val2))
+ continue;
+ matched = false;
+ break;
+ }
+ if (matched)
+ return;
+ }
+ odr_violation_reported = true;
+ if (warning_at (DECL_SOURCE_LOCATION (TYPE_NAME (DECL_CONTEXT (vtable))), 0,
+ "type %qD violates one definition rule ",
+ DECL_CONTEXT (vtable)))
+ inform (DECL_SOURCE_LOCATION (TYPE_NAME (DECL_CONTEXT (prevailing))),
+ "a type with the same name but different virtual table is "
+ "defined in another translation unit");
+}
+
/* Return true if N looks like likely target of a polymorphic call.
Rule out cxa_pure_virtual, noreturns, function declared cold and
other obvious cases. */
Index: ipa-utils.h
===================================================================
--- ipa-utils.h (revision 207702)
+++ ipa-utils.h (working copy)
@@ -92,6 +92,7 @@ bool get_polymorphic_call_info_from_inva
tree, tree, HOST_WIDE_INT);
tree vtable_pointer_value_to_binfo (tree t);
bool vtable_pointer_value_to_vtable (tree, tree *, unsigned HOST_WIDE_INT *);
+void compare_virtual_tables (tree, tree);
/* Return vector containing possible targets of polymorphic call E.
If FINALP is non-NULL, store true if the list is complette.
