With --std=c++11, a template parameter can refer to a local type defined
within a function. Because that local type doesn't qualify for its own
type unit, we copy it as an unworthy type into the type unit that refers
to it, but we copy too much, leading to a comdat type unit that contains a
DIE with subprogram definitions rather than declarations. These DIEs may
have DW_AT_low_pc/high_pc or DW_AT_ranges attributes, and consequently can
refer to range list entries that don't get emitted because they're not
marked when the compile unit is scanned, eventually causing an undefined
symbol at link time.
In addition, while debugging this problem, I found that the
DW_AT_object_pointer attribute, when left in the skeletons that are left
behind in the compile unit, causes duplicate copies of the types to be
copied back into the compile unit.
This patch fixes these problems by removing the DW_AT_object_pointer
attribute from the skeleton left behind in the compile unit, and by
copying DW_TAG_subprogram DIEs as declarations when copying unworthy
types into a type unit. In order to preserve information in the DIE
structure, I also added DW_AT_abstract_origin as an attribute that
should be copied when cloning a DIE as a declaration.
I also fixed the dwarf4-typedef.C test, which should be turning on
the -fdebug-types-section flag.
Bootstrapped and tested on x86. OK for trunk?
-cary
2012-08-07 Cary Coutant ccout...@google.com
gcc/
* dwarf2out.c (clone_as_declaration): Copy DW_AT_abstract_origin
attribute.
(generate_skeleton_bottom_up): Remove DW_AT_object_pointer attribute
from original DIE.
(clone_tree_hash): Rename to ...
(clone_tree_partial): ... this; change callers. Copy
DW_TAG_subprogram DIEs as declarations.
gcc/testsuite/
* testsuite/g++.dg/debug/dwarf2/dwarf4-nested.C: New test case.
* testsuite/g++.dg/debug/dwarf2/dwarf4-typedef.C: Add
-fdebug-types-section flag.
Index: gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-nested.C
===
--- gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-nested.C (revision 0)
+++ gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-nested.C (revision 0)
@@ -0,0 +1,55 @@
+// { dg-do compile }
+// { dg-options --std=c++11 -dA -gdwarf-4 -fdebug-types-section
-fno-merge-debug-strings }
+
+// Check that -fdebug-types-sections does not copy a full referenced type
+// into a type unit.
+
+// Checks that at least one type unit is generated.
+//
+// { dg-final { scan-assembler DIE \\(.*\\) DW_TAG_type_unit } }
+//
+// Check that func is declared exactly twice in the debug info:
+// once in the type unit for struct D, and once in the compile unit.
+//
+// { dg-final { scan-assembler-times \\.ascii
\func0\\[^\n\]*DW_AT_name 2 } }
+//
+// Check to make sure that no type unit contains a DIE with DW_AT_low_pc
+// or DW_AT_ranges. These patterns assume that the compile unit is always
+// emitted after all type units.
+//
+// { dg-final { scan-assembler-not \\.quad.*DW_AT_low_pc.*DIE \\(.*\\)
DW_TAG_compile_unit } }
+// { dg-final { scan-assembler-not \\.quad.*DW_AT_ranges.*DIE \\(.*\\)
DW_TAG_compile_unit } }
+
+struct A {
+ A();
+ virtual ~A();
+ virtual void foo();
+ private:
+ int data;
+};
+
+struct B {
+ B();
+ virtual ~B();
+};
+
+extern B* table[];
+
+struct D {
+ template typename T
+ T* get(int i)
+ {
+B* cell = table[i];
+if (cell == 0)
+ cell = new T();
+return static_castT*(cell);
+ }
+};
+
+void func(D* d)
+{
+ struct C : B {
+A a;
+ };
+ d-getC(0)-a.foo();
+}
Index: gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-typedef.C
===
--- gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-typedef.C (revision 190189)
+++ gcc/testsuite/g++.dg/debug/dwarf2/dwarf4-typedef.C (working copy)
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options -gdwarf-4 } */
+/* { dg-options -gdwarf-4 -fdebug-types-section } */
/* Regression test for an ICE in output_die when using -gdwarf-4. */
Index: gcc/dwarf2out.c
===
--- gcc/dwarf2out.c (revision 190189)
+++ gcc/dwarf2out.c (working copy)
@@ -6357,6 +6357,7 @@ clone_as_declaration (dw_die_ref die)
switch (a-dw_attr)
{
+case DW_AT_abstract_origin:
case DW_AT_artificial:
case DW_AT_containing_type:
case DW_AT_external:
@@ -6489,6 +6490,12 @@ generate_skeleton_bottom_up (skeleton_ch
dw_die_ref clone = clone_die (c);
move_all_children (c, clone);
+/* If the original has a DW_AT_object_pointer attribute,
+ it would now point to a child DIE just moved to the
+ cloned tree, so we need to remove that attribute from
+ the original. */
+remove_AT (c, DW_AT_object_pointer);
+
replace_child (c, clone, prev);
