Here we have (conceptually *) something like

  struct B { };
  struct D : B { };
  D(0); // invalid

and in C++20 the ()-initialization has created a { 0 } constructor that
it tries to initialize an object of type D with.  We should reject
initializing an object of type B from 0, but we wrongly accept it because
process_init_constructor_record skips initializers for empty bases/fields:
       if (DECL_SIZE (field) && integer_zerop (DECL_SIZE (field))
           && !TREE_SIDE_EFFECTS (next))
         /* Don't add trivial initialization of an empty base/field to the
            constructor, as they might not be ordered the way the back-end
            expects.  */
         continue;
but here 'next' was error_mark_node, returned by massage_elt_init, so we
wound up with { } which would validly value-initialize the object.

[*] Usually digest_init in build_new_method_call_1 would detect this,
but in this case the instance is is_dummy_object and we don't call
digest just yet.

        PR c++/94885
        * typeck2.c (process_init_constructor_record): Return PICFLAG_ERRONEOUS
        if an initializer element was erroneous.

        * g++.dg/cpp2a/paren-init26.C: New test.

On Thu, May 07, 2020 at 02:45:29PM +0200, Thomas Schwinge wrote:
> >>+      for (tree op = win; TREE_CODE (op) == COMPOUND_EXPR;
>
> ..., and new 'op' variable here.
>
> >>+        op = TREE_OPERAND (op, 1))
> >>+     v.safe_push (op);
> >>+      FOR_EACH_VEC_ELT_REVERSE (v, i, op)
> >>+     ret = build2_loc (EXPR_LOCATION (op), COMPOUND_EXPR,
> >>+                       TREE_TYPE (win), TREE_OPERAND (op, 0),
> >>+                       ret);
> >>+      return ret;
> >>     }
> >>   while (TREE_CODE (op) == NOP_EXPR)
> >>     {

There is no reason for the shadowing and op at this point acts as a
temporary and will be overwritten in FOR_EACH_VEC_ELT_REVERSE anyway.
So, we can just s/tree // here.

2020-05-08  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/94724
	* tree.c (get_narrower): Reuse the op temporary instead of
	shadowing it.

The deduced return type causes the instantiation of the function body,
which can then require the instantiation of std::projected::operator*
which is intentionally not defined.

This patch uses a helper trait to define the return type, so that the
function body doesn't need to be instantiated.

Unlike on the master branch, this backport to gcc-10 does not change the
iter_rvalue_reference_t alias template and __indirectly_readable_impl
concept to use the new trait.

Backport from mainline
2020-05-01  Jonathan Wakely  <jwakely@redhat.com>
	    Patrick Palka  <ppalka@redhat.com>

	PR libstdc++/92894
	* include/bits/iterator_concepts.h (ranges::__cust_imove::_IMove):
	Add trait to determine return type and an alias for it.
	(ranges::__cust_imove::_IMove::operator()): Use __result instead of
	deduced return type.
	* testsuite/24_iterators/customization_points/92894.cc: New test.
	* testsuite/24_iterators/indirect_callable/92894.cc: New test.

Co-authored-by: Patrick Palka <ppalka@redhat.com>

Here we ICE with -std=c++98 since the newly added call to uses_template_parms
(r10-6357): we hit
26530             gcc_assert (cxx_dialect >= cxx11
26531                         || INTEGRAL_OR_ENUMERATION_TYPE_P (type));
and TYPE is a record type.  The problem is that the argument to
value_dependent_expression_p does not satisfy potential_constant_expression
which it must, as the comment explains.  I thought about fixing this in
uses_template_parms -- only call v_d_e_p if p_c_e is true, but in this
case we want to also suppress the warnings if we don't have a constant
expression.  I couldn't simply check TREE_CONSTANT as in
compute_array_index_type_loc, because then we'd stop warning in the new
Wtype-limits3.C test.

Fixed by using type_dependent_expression_p_push instead.  This means
that we won't suppress the warnings for value-dependent expressions that
aren't type-dependent, e.g. sizeof (T).  This only seems to make a
difference for -Wdiv-by-zero, now tested in Wdiv-by-zero-3.C, where I
think it's reasonable to warn.  It could make -Wtautological-compare
warn more, but that warning doesn't trigger when it gets constant arguments.
Wtype-limits4.C is a test reduced from poly-int.h and it tests a scenario
that was missing in our testsuite.

This patch also moves the warning_sentinels after the RECURs -- we mean
to use them for build_x_binary_op purposes only.

        PR c++/94938
        * pt.c (tsubst_copy_and_build): Call type_dependent_expression_p_push
        instead of uses_template_parms.  Move the warning_sentinels after the
        RECURs.

        * g++.dg/warn/Wdiv-by-zero-3.C: New test.
        * g++.dg/warn/Wtype-limits4.C: New test.
        * g++.dg/warn/template-2.C: New test.
        * g++.old-deja/g++.pt/crash10.C: Add dg-warning.

Essentially the same fix as for x86.

2020-05-07  Uroš Bizjak  <ubizjak@gmail.com>

gcc/
	* config/alpha/alpha.c (alpha_atomic_assign_expand_fenv): Use
	TARGET_EXPR instead of MODIFY_EXPR for the first assignments to
	fenv_var and new_fenv_var.

	Backport from mainline
	2020-05-07  Martin Liska  <mliska@suse.cz>

	* doc/invoke.texi: Fix 2 optindex entries.

The testcase in the current form doesn't FAIL without the patch on
x86_64-linux unless also testing with -m32; as that the 64-bit testing
on that target is probably way more common, and we can use also attributes
that FAIL without the patch with -m64, the following patch adjusts the
test, so that it FAILs without the patch for both -m64 and -m32 (but not
-mx32) and PASSes with the patch.

2020-05-07  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94946
	* g++.dg/ext/attr-parm-1.C: Enable the test also for lp64 x86, use
	sysv_abi and ms_abi attributes in that case instead of fastcall and
	no attribute.

If the second argument of __builtin_speculation_safe_value is
error_mark_node (or has such a type), we ICE during
useless_typ_conversion_p.

202-05-07  Jakub Jelinek  <jakub@redhat.com>

	PR c/94968
	* c-common.c (speculation_safe_value_resolve_params): Return false if
	error_operand_p (val2).
	(resolve_overloaded_builtin) <case BUILT_IN_SPECULATION_SAFE_VALUE_N>:
	Remove extraneous semicolon.

	* gcc.dg/pr94968.c: New test.

The following testcase gets a bogus warning during build_base_path,
when cp_build_indirect_ref* calls strict_aliasing_warning with a dependent
expression.  IMHO calling get_alias_set etc. on dependent types feels wrong
to me, we should just defer the warnings in those cases until instantiation
and only handle the cases where neither type nor expr are dependent.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94951
	* typeck.c (cp_strict_aliasing_warning): New function.
	(cp_build_indirect_ref_1, build_reinterpret_cast_1): Use
	it instead of strict_aliasing_warning.

	* g++.dg/warn/Wstrict-aliasing-bogus-tmpl.C: New test.

On the following testcase we ICE, because synthesize_method is called twice
on the same sfk_comparison method fndecl, the first time it works fine
because start_preparsed_function in that case sets both
current_function_decl and cfun, but second time it is called it only sets
the former and keeps cfun NULL, so we ICE when trying to store
current_function_returns_value.
I think it is just wrong to call synthesize_method multiple times, and most
synthesize_method callers avoid that by not calling it if DECL_INITIAL is
already set, so this patch does that too.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94907
	* method.c (defaulted_late_check): Don't call synthesize_method
	on constexpr sfk_comparison if it has been called on it already.

	* g++.dg/cpp2a/spaceship-synth8.C: New test.

Similarly to the fixes on many other targets, riscv needs to use TARGET_EXPR
to avoid having the create_tmp_var_raw temporaries without proper DECL_CONTEXT
and not mentioned in local decls.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR target/94950
	* config/riscv/riscv-builtins.c (riscv_atomic_assign_expand_fenv): Use
	TARGET_EXPR instead of MODIFY_EXPR for first assignment to old_flags.

There were some discussions about whether REG_EQUAL notes are valid on insns with a single
set which contains auto-inc-dec side-effects in the SET_SRC and the majority thinks that
it should be valid.  So, this patch fixes the combiner to punt in that case, because otherwise
the auto-inc-dec side-effects from the SET_SRC are lost.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/94873
	* combine.c (combine_instructions): Don't optimize using REG_EQUAL
	note if SET_SRC (set) has side-effects.

	* gcc.dg/pr94873.c: New test.

This insn and split splits into HI->V?HImode broadcast for avx2 and later,
but either the operands need to be %xmm0-%xmm15 (i.e. VEX encoded insn), or
the insn needs both AVX512BW and AVX512VL.
Now, Yv constraint is v for AVX512VL and x otherwise, so for -mavx512vl -mno-avx512bw
we ICE if we end up with a %xmm16+ register from RA.
Yw constraint is v for AVX512VL and AVX512BW and nothing otherwise, so
in this pattern we actually need xYw.

2020-05-05  Jakub Jelinek  <jakub@redhat.com>

	PR target/94942
	* config/i386/mmx.md (*vec_dupv4hi): Use xYw constraints instead of Yv.

	* gcc.target/i386/pr94942.c: New test.

While testing the --with-documentation-root-url= changes, I run into
[Wreturn-type] URL pointing to gfortran documentation where it obviously
isn't documented.  The following patch updates the list of options to match
reality (on the other side -Wconversion-extra is gfortran only option
documented in gfortran.texi).

Or, perhaps better use the attached patch instead, which doesn't have a
hardcoded list and instead uses the flags?  I went through options.c
and the updated list of options matches exactly the cases where CL_Fortran
is set for "-W*" options together with CL_C and/or CL_CXX (ok, there is also
-Wall and -Wextra, but hopefully we don't emit [Wall] or [Wextra] for
anything).

2020-05-04  Jakub Jelinek  <jakub@redhat.com>

	* opts.c (get_option_html_page): Instead of hardcoding a list of
	options common between C/C++ and Fortran only use gfortran/
	documentation for warnings that have CL_Fortran set but not
	CL_C or CL_CXX.

If there are _Atomic side-effects in the parameter declarations
of non-nested function, when they are parsed, current_function_decl is
NULL, the create_artificial_label created labels during build_atomic* are
then adjusted by store_parm_decls through set_labels_context_r callback.
Unfortunately, if such thing happens in nested function parameter
declarations, while those decls are parsed current_function_decl is the
parent function (and am not sure it is a good idea to temporarily clear it,
some code perhaps should be aware it is in a nested function, or it can
refer to variables from the parent function etc.) and that means
store_param_decls through set_labels_context_r doesn't adjust anything.
As those labels are emitted in the nested function body rather than in the
parent, I think it is ok to override the context in those cases.

2020-04-30  Jakub Jelinek  <jakub@redhat.com>

	PR c/94842
	* c-decl.c (set_labels_context_r): In addition to context-less
	LABEL_DECLs adjust also LABEL_DECLs with context equal to
	parent function if any.
	(store_parm_decls): Adjust comment.

	* gcc.dg/pr94842.c: New test.

2020-05-07  Jakub Jelinek  <jakub@redhat.com>

	* BASE-VER: Set to 10.1.1.

2020-05-07  Jakub Jelinek  <jakub@redhat.com>

	* gennews (files): Add files for GCC 10.

This uses a target spec to test only on ia32 targets

Jason's fix for 90570 & 79585 was a bit overzealous.  Dependent attribs should still
attach to a parameter decl.

	* decl.c (grokdeclarator): Don't splice template attributes in
	parm context -- they can apply to the parm.

This version of the fix uses __getauxval instead of getauxval.
The whole thing is guarded simply on __gnu_linux__.
__getauxval was introduced in 2.16 but the aarch64 port was added in 2.17 so in practice I expect all aarch64 glibcs to support __getauxval.

Bootstrapped and tested on aarch64-none-linux-gnu.
Also tested on aarch64-none-elf.

2020-05-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

	* config/aarch64/lse-init.c (init_have_lse_atomics): Use __getauxval
	instead of getauxval.
	(AT_HWCAP): Define.
	(HWCAP_ATOMICS): Define.
	Guard detection on __gnu_linux__.

	* config/abi/post/x86_64-linux-gnu/x32/baseline_symbols.txt: Updated.

I just remembered that the libstdc++ ABI baselines haven't been updated
for the GCC 10 release yet.  This patch corrects this for Solaris/SPARC
and x86.

Created on master with make new-abi-baseline on i386-pc-solaris2.11 and
sparc-sun-solaris2.11, bootstrapped on gcc-10 branch without regressions.

	* config/abi/post/i386-solaris/baseline_symbols.txt: Regenerate.
	* config/abi/post/i386-solaris/amd64/baseline_symbols.txt:
	Likewise.
	* config/abi/post/sparc-solaris/baseline_symbols.txt: Likewise.
	* config/abi/post/sparc-solaris/sparcv9/baseline_symbols.txt:
	Likewise.

	* doc/xml/manual/abi.xml (abi.versioning.history): Document library
	versions for GCC 9.[123] and 10.1 releases.
	* doc/html/*: Regenerate.

On Wed, May 06, 2020 at 10:49:13AM +0200, Rainer Orth wrote:
> I just remembered that the libstdc++ ABI baselines haven't been updated
> for the GCC 10 release yet.  This patch corrects this for Solaris/SPARC
> and x86.

Oops, here are the updates from Fedora packages built during the weekend.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	* config/abi/post/x86_64-linux-gnu/baseline_symbols.txt: Update.
	* config/abi/post/x86_64-linux-gnu/32/baseline_symbols.txt: Update.
	* config/abi/post/i386-linux-gnu/baseline_symbols.txt: Update.
	* config/abi/post/i486-linux-gnu/baseline_symbols.txt: Update.
	* config/abi/post/aarch64-linux-gnu/baseline_symbols.txt: Update.
	* config/abi/post/s390x-linux-gnu/baseline_symbols.txt: Update.
	* config/abi/post/powerpc64-linux-gnu/baseline_symbols.txt: Update.

This patch updates install.texi for GCC 10 on Solaris.  It includes some
general cleanup and updates and includes a couple of caveats, some of
them found when testing GCC 10.1.0 RC1 with only the bundled tools.

The reference to TGCware on the binaries page is gone because they only
provide binaries up to Solaris 9.

The note about configuring 64-bit Solaris/SPARC compilers with
--build=sparcv9-sun-solaris2.11 became necessary because upstream
config.guess silently reverted my patch to automatically detect this.  We
already had a bug report about a comparison failure caused by this issue.

Tested with make doc/gccinstall.info and doc/gccinstall.pdf and
inspection of the resulting files.

	* doc/install.texi: Replace Sun with Solaris as appropriate.
	(Tools/packages necessary for building GCC, Perl version between
	5.6.1 and 5.6.24): Remove Solaris 8 reference.
	(Installing GCC: Binaries, Solaris 2 (SPARC, Intel)): Remove
	TGCware reference.
	(Specific, i?86-*-solaris2*): Update version references for
	Solaris 11.3 and later.  Remove gas 2.26 caveat.
	(Specific, *-*-solaris2*): Update version references for
	Solaris 11.3 and later.  Remove boehm-gc reference.
	Document GMP, MPFR caveats on Solaris 11.3.
	(Specific, sparc-sun-solaris2*): Update Solaris 9 references.
	(Specific, sparc64-*-solaris2*): Likewise.
	Document --build requirement.

I've recently tested i386-pc-solaris2.11 bootstrap on Solaris 11/x86
with only the bundled tools (using /usr/gnu/bin/as from binutils 2.30 in
this case).  It failed compiling libgo/runtime/proc.c, creating invalid
assembly:

proc.s: Assembler messages:
proc.s:2092: Error: junk at end of line, first unrecognized character is `*'

        .globl  __emutls_v.*runtime.g

and several more errors.  This is completely unexpected since Solaris
does support TLS.  It turned out that 32-bit TLS detection in
gcc/configure had failed:

configure:25145: checking assembler for thread-local storage support
configure:25158: /usr/gnu/bin/as   --fatal-warnings -o conftest.o conftest.s >&5
conftest.s: Assembler messages:
conftest.s:6: Error: relocated field and relocation type differ in signedness
conftest.s:7: Error: @TLSLDM reloc is not supported with 64-bit output format
conftest.s:7: Error: junk `@tlsldm' after expression

which isn't unexpected given that the bundled gas has been configured
for x86_64-pc-solaris2.11, i.e. 64-bit-default.

This is easily fixed by explicitly passing --32 for the 32-bit case,
matching what is done for the 64-bit test.

Tested on i386-pc-solaris2.11 with 32-bit-default and 64-bit-default gas
as well as with /usr/bin/as, always correctly detecting TLS support.

	* configure.ac <i[34567]86-*-*>: Add --32 to tls_as_opt on Solaris.
	* configure: Regenerate.

The previous URL to an entry in the wayback machine now redirects to a
page saying "SGI.com Tech Archive Resources now retired" so use an older
entry from the archive.

	* doc/xml/faq.xml: Use working link for SGI STL FAQ.
	* doc/html/*: Regenerate.

This fixes two compilation errors preventing bootstrap with Ada
on x86_64-pc-cygwin.

2020-05-04  Mikael Pettersson  <mikpelinux@gmail.com>

	PR bootstrap/94918
	* mingw32.h: Prevent windows.h from including emmintrin.h on Cygw64.
	* s-oscons-tmplt.c (Serial_Port_Descriptor): Use System.Win32.HANDLE
	also on Cygwin.

create_output_operand coerces an output operand to the insn's
predicates, using a suggested rtx location if convenient.
But if that rtx location is actually required rather than
optional, the builder of the insn has to emit a move afterwards.

(We could instead add a new interface that does this automatically,
but that's future work.)

This PR shows that we were failing to emit the move for some of the
vector load internal functions.  I think there are other routines in
internal-fn.c that potentially have the same problem, but this patch is
supposed to be a conservative subset suitable for backporting to GCC 10.

2020-05-04  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR middle-end/94941
	* internal-fn.c (expand_load_lanes_optab_fn): Emit a move if the
	chosen lhs is different from the gcall lhs.
	(expand_mask_load_optab_fn): Likewise.
	(expand_gather_load_optab_fn): Likewise.

gcc/testsuite/
	PR middle-end/94941
	* gcc.target/aarch64/sve/acle/general/unoptimized_1.c: New test.

	* sv.po: Update.

	Revert:
	2020-04-30  Marek Polacek  <polacek@redhat.com>

	PR c++/94775
	* tree.c (check_base_type): Return true only if TYPE_USER_ALIGN match.
	(check_aligned_type): Check if TYPE_USER_ALIGN match.