The following fixes an ICE with -flto -ffat-lto-objects
-fdebug-types-section -g where optimize_external_refs does not
expect to see DW_AT_signature as made "local" by build_abbrev_table(sic!).
This is because we run optimize_external_refs twice in this setup.
The fix is to make the second run not pick up "local" DW_AT_signature
as external. Alternatively build_abbrev_table could be adjusted
to not keep those as DW_AT_signature. It's not even clear to me
whether a DW_AT_signature as we output it is valid DWARF ...
to quote non-LTO -g:
<1><1d>: Abbrev Number: 13 (DW_TAG_structure_type)
<1e> DW_AT_name : (indirect string, offset: 0x8b):
integral_constant<bool, false>
<22> DW_AT_signature : <0x5d>
<26> DW_AT_declaration : 1
<26> DW_AT_sibling : <0x48>
...
<1><5d>: Abbrev Number: 16 (DW_TAG_structure_type)
<5e> DW_AT_name : (indirect string, offset: 0x8b):
integral_constant<bool, false>
<62> DW_AT_signature : signature: 0x1f6a4ae7cc5a362e
<6a> DW_AT_declaration : 1
<6a> DW_AT_sibling : <0x7b>
13 DW_TAG_structure_type [has children]
DW_AT_name DW_FORM_strp
DW_AT_signature DW_FORM_ref4
16 DW_TAG_structure_type [has children]
DW_AT_name DW_FORM_strp
DW_AT_signature DW_FORM_ref_sig8
Using DW_AT_specification (as other code in dwarf seems to try
doing) seems fishy as well given the refering DIE is
DW_AT_declaration...
The DWARF spec doesn't seem to explicitely list an appropriate
refering attribute type that is applicable here. My favorite
kitchen-sink DW_AT_abstract_origin might count ;)
Of ocurse the main "issue" is that copy_unworthy_types
duplicated this parent into 1d and 5d in the first place
(but that's a pure optimization issue?). Not doing that
would have avoided the situation in PR87295. But then
why should optimize_external_refs_1 have this special
code handling DW_AT_signature in the first place if this
was not intended... (so even better, kill that and the
build_abbrev_table optimization and fix copy_unworthy_types?)
Oh, and insert rants of -fdebug-types-section not being
used by anybody.
Bootstrap & regtest running on x86_64-unknown-linux-gnu, OK?
Thanks,
Richard.
2019-01-25 Richard Biener <rguent...@suse.de>
PR debug/87295
* dwarf2out.c (optimize_external_refs_1): Do not pick up
already optimized DW_AT_signature refs.
* g++.dg/lto/pr87295_0.C: New testcase.
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c (revision 268260)
+++ gcc/dwarf2out.c (working copy)
@@ -8911,7 +8911,11 @@ optimize_external_refs_1 (dw_die_ref die
struct external_ref *ref_p;
if (is_type_die (die)
- && (c = get_AT_ref (die, DW_AT_signature)))
+ && (c = get_AT_ref (die, DW_AT_signature))
+ /* Make sure to not pick up optimized local refs from the
+ early LTO run of build_abbrev_table which performs the
+ actual redirection. */
+ && c->comdat_type_p)
{
/* This is a local skeleton; use it for local references. */
ref_p = lookup_external_ref (map, c);
Index: gcc/testsuite/g++.dg/lto/pr87295_0.C
===================================================================
--- gcc/testsuite/g++.dg/lto/pr87295_0.C (nonexistent)
+++ gcc/testsuite/g++.dg/lto/pr87295_0.C (working copy)
@@ -0,0 +1,20 @@
+// { dg-lto-do assemble }
+// { dg-lto-options { { -flto -ffat-lto-objects -fdebug-types-section -g
-std=gnu++17 } } }
+
+template<typename _Tp, _Tp __v>
+struct integral_constant
+{
+ static constexpr _Tp value = __v;
+ typedef _Tp value_type;
+ constexpr operator value_type() const noexcept { return value; }
+};
+
+typedef integral_constant<bool, false> false_type;
+
+template<typename...>
+struct __or_;
+
+template<>
+struct __or_<>
+ : public false_type
+{ };
