On Tue, Nov 14, 2017 at 07:34:54AM +0100, Richard Biener wrote:
> On November 14, 2017 6:21:41 AM GMT+01:00, Jason Merrill <ja...@redhat.com>
> wrote:
> >On Mon, Nov 13, 2017 at 1:02 PM, Marek Polacek <pola...@redhat.com>
> >> In the end I did two bootstraps with the patch, but modifed one of
> >them
> >> to always return false for ix86_is_empty_record. Then I compared all
> >the
> >> *.o in both dirs. The result is attached. Then I looked at
> >DW_AT_producer
> >> for all these .o that differ; all of them are C++. Is this enough to
> >> clear our concerns?
> >
> >Hmm, a bunch of these are right at the beginning, bytes 41 and 65, in
> >the header.
> >
> >Did you build them in the different trunk/trunk2 directories? I think
> >Jakub was suggesting building them in the same directory.
> >> And I also ran a bootstrap with --enable-cxx-flags=-Wabi=11, and
> >didn't
> >> see any warnings.
> >
> >If there's a codegen change, there ought to be a warning to go along
> >with it.
>
> The question was of course also for unintended changes but yes (I was mainly
> concerned by libstdc++ ABI changes).
Ok, I did two bootstraps in the same dir, one with ix86_is_empty_record always
returning false. There were a few object files that differ in their assembly
between those two bootstraps. Previously I didn't see any warnings because
I hadn't thought of -Wsystem-headers. Also, we intentionally don't warn if
the empty parameter is the last one:
+ bool seen_empty_type = false;
+ FOREACH_FUNCTION_ARGS (fntype, argtype, iter)
+ {
+ if (VOID_TYPE_P (argtype))
+ break;
+ if (TYPE_EMPTY_P (argtype))
+ seen_empty_type = true;
+ else if (seen_empty_type)
+ {
+ cum->warn_empty = true;
+ break;
+ }
+ }
After enabling -Wsystem-headers and tweaking the code above so that we warn
even if the empty parameter is trailing I can see the warnings that correspond
to the assembly changes. Below is a summary of what I found. TL;DR: I don't
see any unintended changes.
gcc/gcov.o
includes #define INCLUDE_ALGORITHM so we'll get bits/stl_algo.h with stuff
like
bits/stl_algo.h:1840:5: warning: empty class
‘__gnu_cxx::__ops::_Iter_comp_iter<function_line_start_cmp>’
__insertion_sort(_RandomAccessIterator __first,
gcc/go/gogo.o
includes bits/stl_vector.h:
1535 _M_range_insert(__pos, __first, __last,
1536 std::__iterator_category(__first));
warning: empty class ‘std::forward_iterator_tag’
gcc/go/expressions.o
gcc/go/export.o
includes bits/stl_algo.h:
std::__insertion_sort(__first, __last, __comp);
warning: empty class ‘__gnu_cxx::__ops::_Iter_less_iter’
gcc/go/types.o
includes bits/stl_algo.h:
std::__final_insertion_sort(__first, __last, __comp);
warning: empty class
‘__gnu_cxx::__ops::_Iter_comp_iter<Typed_identifier_list_sort>’
gcc/go/statements.o
bits/hashtable.h:2068:4: warning: empty class ‘std::integral_constant<bool,
true>’
gcc/build/genrecog.o
includes #define INCLUDE_ALGORITHM
warning: empty class ‘__gnu_cxx::__ops::_Iter_less_iter’
342 std::__adjust_heap(__first, __parent, __len,
_GLIBCXX_MOVE(__value),
343 __comp);
gcc/i386.o
gcc/bb-reorder.o
expected changes
gcc/tree-loop-distribution.o
uses std::stable_sort
x86_64-pc-linux-gnu/libstdc++-v3/src/c++98/bitmap_allocator.o
./src/c++98/bitmap_allocator.cc
57 iterator __tmp = __lower_bound(__free_list.begin(), __free_list.end(),
58 __sz, _LT_pointer_compare());
warning: empty class ‘__gnu_cxx::free_list::_LT_pointer_compare’
x86_64-pc-linux-gnu/libstdc++-v3/src/c++98/messages_members.o
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/sstream-inst.o
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/cxx11-wlocale-inst.o
includes bits/basic_string.h:
236 _M_construct(__beg, __end, _Tag());
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/cow-shim_facets.o
includes c++11/cxx11-shim_facets.cc:
271 return __collate_compare(other_abi{}, _M_get(),
272 lo1, hi1, lo2, hi2);
warning: empty class ‘std::integral_constant<bool, true>’
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/cow-string-inst.o
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/string-inst.o
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/cow-wstring-inst.o
includes basic_string.tcc:
563 basic_string<_CharT, _Traits, _Alloc>::
564 _S_construct(_InIterator __beg, _InIterator __end, const _Alloc&
__a,
565 forward_iterator_tag)
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/cxx11-shim_facets.o
see above
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/locale-inst.o
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/wlocale-inst.o
includes bits/basic_string.h:
5033 return _S_construct(__beg, __end, __a, _Tag());
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/c++11/wstring-inst.o
includes bits/basic_string.tcc:
206 basic_string<_CharT, _Traits, _Alloc>::
207 _M_construct(_InIterator __beg, _InIterator __end,
208 std::forward_iterator_tag)
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/ops.o
includes bits/stl_deque.h:
2012 _M_range_insert_aux(__pos, __first, __last,
2013 std::__iterator_category(__first));
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/cow-path.o
includes bits/basic_string.tcc:
1104 basic_string<_CharT, _Traits, _Alloc>::
1105 _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator
__k1,
1106 _InputIterator __k2, __false_type)
warning: empty class ‘std::__false_type’
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/cow-std-ops.o
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/std-ops.o
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/cow-ops.o
includes bits/deque.tcc:
586 _M_range_insert_aux(iterator __pos,
587 _ForwardIterator __first, _ForwardIterator
__last,
588 std::forward_iterator_tag)
warning: empty class ‘std::forward_iterator_tag’
x86_64-pc-linux-gnu/libstdc++-v3/src/filesystem/cow-std-path.o
includes bits/basic_string.h:
4884 return _M_replace_dispatch(__i1, __i2, __k1, __k2,
_Integral());
warning: empty class ‘std::__false_type’
x86_64-pc-linux-gnu/libsanitizer/asan/asan_memory_profile.o
warning: empty class ‘__asan::HeapProfile::Print(__sanitizer::uptr,
__sanitizer::uptr)::<lambda(const __asan::AllocationSite&, const
__asan::AllocationSite&)>’ parameter passing ABI changes in -fabi-version=12
(GCC 8) [-Wabi]
void InternalSort(Container *v, uptr size, Compare comp) {
x86_64-pc-linux-gnu/libsanitizer/asan/asan_interceptors.o
sanitizer_common_interceptors_ioctl.inc:477:15: warning: empty class
‘ioctl_desc_compare’ parameter passing ABI changes in -fabi-version=12 (GCC 8)
[-Wabi]
InternalSort(&ioctl_table, ioctl_table_size, ioctl_desc_compare());
x86_64-pc-linux-gnu/libsanitizer/asan/.libs/asan_memory_profile.o
asan_memory_profile.cc:50:17: warning: empty class
‘__asan::HeapProfile::Print(__sanitizer::uptr,
__sanitizer::uptr)::<lambda(const __asan::AllocationSite&, const
__asan::AllocationSite&)>’ parameter passing ABI changes in -fabi-version=12
(GCC 8) [-Wabi]
InternalSort(&allocations_, allocations_.size(),
~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[](const AllocationSite &a, const AllocationSite &b) {
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
return a.total_size > b.total_size;
x86_64-pc-linux-gnu/libsanitizer/asan/.libs/asan_interceptors.o
sanitizer_common.h:573:6: warning: empty class ‘ioctl_desc_compare’ parameter
passing ABI changes in -fabi-version=12 (GCC 8) [-Wabi]
void InternalSort(Container *v, uptr size, Compare comp) {
x86_64-pc-linux-gnu/libsanitizer/tsan/tsan_interceptors.o
x86_64-pc-linux-gnu/libsanitizer/tsan/.libs/tsan_interceptors.o
sanitizer_common_interceptors_ioctl.inc:477:15: warning: empty class
‘ioctl_desc_compare’ parameter passing ABI changes in -fabi-version=12 (GCC 8)
[-Wabi]
InternalSort(&ioctl_table, ioctl_table_size, ioctl_desc_compare());
Marek
