Remove all user-level documentation of the check name
"Atomic_Synchronization". The documentation was confusing because
this check should never be used in source code, and because it
raises the question of whether All_Checks applies to it (it does
not).

Change the name Atomic_Synchronization to be _Atomic_Synchronization
(with a leading underscore) so that it cannot be used in source code.

This "check" is not really a check at all; it is used only internally in
the implementation of Disable/Enable_Atomic_Synchronization, because the
placement and scope of these pragmas match pragma Suppress.

gcc/ada/ChangeLog:

	* doc/gnat_rm/implementation_defined_characteristics.rst:
	Remove Atomic_Synchronization.
	* doc/gnat_ugn/building_executable_programs_with_gnat.rst:
	Likewise.
	* doc/gnat_rm/implementation_defined_pragmas.rst: DRY.
	Consolidate documentation of Disable/Enable_Atomic_Synchronization.
	* checks.adb: Comment fix.
	* exp_util.ads: Likewise.
	* targparm.ads: Likewise.
	* types.ads: Likewise.
	* gnat1drv.adb: Likewise. DRY.
	* sem_prag.adb (Process_Disable_Enable_Atomic_Sync):
	Change name of Atomic_Synchronization to start with
	underscore.
	(Process_Suppress_Unsuppress): No need to check Comes_From_Source for
	Atomic_Synchronization anymore; _Atomic_Synchronization can never
	come from source. (Anyway, it shouldn't be ignored; it should be
	an error.)
	* snames.ads-tmpl (Atomic_Synchronization):
	Change name to start with underscore.
	* switch-c.adb (Scan_Front_End_Switches):
	Minor cleanup: Use 'in'.
	* gnat_rm.texi: Regenerate.
	* gnat_ugn.texi: Regenerate.

In addition to Resolve_Indexed_Component, Eval_Indexed_Component can also
set the Do_Range_Check flag on the expressions of an N_Indexed_Component
node through the call on Check_Non_Static_Context, so this also needs to
be blocked by the Kill_Range_Check flag.

gcc/ada/ChangeLog:

	* sem_eval.adb (Eval_Indexed_Component): Clear Do_Range_Check on
	the expressions if Kill_Range_Check is set on the node.

This is another glitch associated with Initialization_Statements.

gcc/ada/ChangeLog:

	* exp_util.adb (Remove_Init_Call): Rewrite a compound statement in
	the Initialization_Statements of the variable as a null statement
	instead of removing it.
	* freeze.adb (Explode_Initialization_Compound_Statement): Small
	comment tweaks.

The processing of static array aggregates in Exp_Aggr requires that their
bounds be representable as Int(eger) values for practical purposes, and
the previous changes have exposed another path where this is not checked.

This introduces a UI_Are_In_Int_Range local predicate for convenience.

gcc/ada/ChangeLog:

	* exp_aggr.adb (UI_Are_In_Int_Range): New predicate.
	(Aggr_Size_OK): Use it.
	(Flatten): Likewise.
	(Packed_Array_Aggregate_Handled): Likewise.
	(Static_Array_Aggregate): Likewise.

The problem occurs for an anonymous array object declared with an aspect and
when pragma {Initialize,Normalize}_Scalars is in effect: in this case, the
synthesized aggregate is attached to the Initialization_Statements field by
Convert_Aggr_In_Object_Decl, but Explode_Initialization_Compound_Statement
puts it back at the point of declaration instead of the freeze point, thus
voiding the effects of the mechanism.

This was previously hidden because of a bypass in Freeze_Entity which drops
the freeze node on the floor in this case, so the change fixes the issue and
removes the bypass in the process.

gcc/ada/ChangeLog:

	* freeze.ads (Explode_Initialization_Compound_Statement): Adjust the
	description.
	* freeze.adb (Explode_Initialization_Compound_Statement): If the
	entity has its freezing delayed, append the initialization actions
	to its freeze actions.
	(Freeze_Object_Declaration): Remove commented out code.
	(Freeze_Entity): Remove bypass for object of anonymous array type.

The exception handler that catches Abort_Signal does nothing nowadays.
This refactors the code to use Build_Abort_Block more consistently and
also makes it simpler by dropping the identifier on the abort block.

No functional changes.

gcc/ada/ChangeLog:

	* exp_sel.ads (Build_Abort_Block): Remove second parameter and
	rename the third.
	(Build_Abort_Block_Handler): Fix description.
	* exp_sel.adb (Build_Abort_Block): Remove second parameter, rename
	the third and adjust accordingly.
	* exp_ch9.adb (Expand_N_Asynchronous_Select): Fix the description
	of the exception handler throughout.  Remove Abort_Block_Ent and
	Hdle local variables.  Call Build_Abort_Block consistently to build
	the abort block and adjust existing calls.

In some cases an array aggregate with statically known bounds and at least
one bound outside of the range of a 32-bit signed integer causes
a bugbox.

gcc/ada/ChangeLog:

	* exp_aggr.adb (Convert_To_Positional.Flatten): Avoid raising
	Constraint_Error in UI_To_Int by testing UI_Is_In_Int_Range first.

This mainly decouples the handling of the declaration case from that of the
assignment case in Expand_Array_Aggregate, as well as moves the expansion
in the case of an aggregate that can be processed by the back end to the
Build_Array_Aggr_Code routine.

gcc/ada/ChangeLog:

	* exp_aggr.adb (Build_Array_Aggr_Code): Build the simple assignment
	for the case of an aggregate that can be handled by the back end.
	(Expand_Array_Aggregate): Adjust description of the processing.
	Move handling of declaration case to STEP 4 and remove handling of
	the case of an aggregate that can be processed by the back end.
	(Late_Expansion): Likewise for the second part.
	* exp_ch3.adb (Expand_N_Object_Declaration): Deal with a delayed
	aggregate synthesized for the default initialization, if any.
	* sem_eval.adb (Eval_Indexed_Component): Bail out for the name of
	an assignment statement.

This mainly decouples the handling of the allocator case from that of the
assignment case in Expand_Array_Aggregate and also makes Must_Slide a bit
more forgiving.

gcc/ada/ChangeLog:

	* exp_aggr.adb (In_Place_Assign_OK): Remove handling of allocators
	and call Must_Slide instead of implementing the check manually.
	(Convert_To_Assignments): Adjust outdated comment.
	(Expand_Array_Aggregate): Move handling of allocator case to STEP 3
	and call Must_Slide directly for it.
	(Must_Slide): Replace tests based on Is_OK_Static_Expression with
	tests based on Compile_Time_Known_Value.

Convert_Array_Aggr_In_Allocator does nothing that Late_Expansion cannot do,
so this deletes the former and moves its support code for Storage_Model to
the latter.  No functional changes.

gcc/ada/ChangeLog:

	* exp_aggr.adb (Convert_Array_Aggr_In_Allocator): Delete.
	(Convert_Aggr_In_Allocator): Do not call above procedure.
	(Late_Expansion): Deal with a target that is the dereference of a
	prefix with a Storage_Model.  Remove an useless actual parameter
	in the call to Build_Array_Aggr_Code.

Reverse the meaning of switch -gnatd_P; that is, enable by default
the generating of a runtime check when the prefix of the call is
an access-to-subprogram type with a null value.

gcc/ada/ChangeLog:

	* sem_res.adb (Resolve_Actuals): Add by default a null-exclusion
	check on the prefix of the call when it is an access-type; it can
	be disabled using -gnatd_P.
	* debug.adb (gnatd_P): Update documentation.

This patch fixes a crash in the compiler when the actual for an anonymous
access type formal is an 'Access of a Sream_Element_Array object during
the calculation of said actual's accessibility level.

gcc/ada/ChangeLog:

	* accessibility.adb (Accessibility_Level): Handle the Input attribute
	case

This change is part of an effort to reduce usage of
Is_Predefined_Filename.

gcc/ada/ChangeLog:

	* frontend.adb (Frontend): tweak test for predefined main unit.

libgomp/ChangeLog:

	* plugin/plugin-gcn.c (GOMP_OFFLOAD_openacc_async_construct): In
	case of an error, call GOMP_PLUGIN_fatal not ..._error; use NULL
	not false in return.

The test file pr117093.c failed on platforms other than aarch64, because
it uses arm_neon.h. We moved it into gcc.target/aarch64.

The patch was bootstrapped and tested on aarch64-linux-gnu and
x86_64-linux-gnu, no regression.
Committed as obvious.

Signed-off-by: Jennifer Schmitz <jschmitz@nvidia.com>

gcc/testsuite/
	PR tree-optimization/117093
	* gcc.dg/tree-ssa/pr117093.c: Move to gcc.target/aarch64.
	* gcc.target/aarch64/pr117093.c: New test.

This patch adds VLS modes to the strided load expanders.

gcc/ChangeLog:

	* config/riscv/autovec.md: Add VLS modes.
	* config/riscv/vector-iterators.md: Ditto.
	* config/riscv/vector.md: Ditto.

This patch adds else operands to masked loads.  Currently the default
else operand predicate just accepts "undefined" (i.e. SCRATCH) values.

	PR middle-end/115336
	PR middle-end/116059

gcc/ChangeLog:

	* config/riscv/autovec.md: Add else operand.
	* config/riscv/predicates.md (maskload_else_operand): New
	predicate.
	* config/riscv/riscv-v.cc (get_else_operand): Remove static.
	(expand_load_store): Use get_else_operand and adjust index.
	(expand_gather_scatter): Ditto.
	(expand_lanes_load_store): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/pr115336.c: New test.
	* gcc.target/riscv/rvv/autovec/pr116059.c: New test.

gcc/ChangeLog:

	* config/i386/sse.md (maskload<mode><sseintvecmodelower>):
	Call maskload<mode>..._1.
	(maskload<mode><sseintvecmodelower>_1): Rename.

This patch adds an undefined else operand to the masked loads.

gcc/ChangeLog:

	* config/gcn/predicates.md (maskload_else_operand): New
	predicate.
	* config/gcn/gcn-valu.md: Use new predicate.

This adds zero else operands to masked loads and their intrinsics.
I needed to adjust more than initially thought because we rely on
combine for several instructions and a change in a "base" pattern
needs to propagate to all those.

gcc/ChangeLog:

	* config/aarch64/aarch64-sve-builtins-base.cc: Add else
	handling.
	* config/aarch64/aarch64-sve-builtins.cc (function_expander::use_contiguous_load_insn):
	Ditto.
	* config/aarch64/aarch64-sve-builtins.h: Add else operand to
	contiguous load.
	* config/aarch64/aarch64-sve.md (@aarch64_load<SVE_PRED_LOAD:pred_load>
	_<ANY_EXTEND:optab><SVE_HSDI:mode><SVE_PARTIAL_I:mode>):
	Split and add else operand.
	(@aarch64_load_<ANY_EXTEND:optab><SVE_HSDI:mode><SVE_PARTIAL_I:mode>):
	Ditto.
	(*aarch64_load_<ANY_EXTEND:optab>_mov<SVE_HSDI:mode><SVE_PARTIAL_I:mode>):
	Ditto.
	* config/aarch64/aarch64-sve2.md: Ditto.
	* config/aarch64/iterators.md: Remove unused iterators.
	* config/aarch64/predicates.md (aarch64_maskload_else_operand):
	Add zero else operand.

This patch adds an else operand to vectorized masked load calls.
The current implementation adds else-value arguments to the respective
target-querying functions that is used to supply the vectorizer with the
proper else value.

We query the target for its supported else operand and uses that for the
maskload call.  If necessary, i.e. if the mode has padding bits and if
the else operand is nonzero, a VEC_COND enforcing a zero else value is
emitted.

gcc/ChangeLog:

	* optabs-query.cc (supports_vec_convert_optab_p): Return icode.
	(get_supported_else_val): Return supported else value for
	optab's operand at index.
	(supports_vec_gather_load_p): Add else argument.
	(supports_vec_scatter_store_p): Ditto.
	* optabs-query.h (supports_vec_gather_load_p): Ditto.
	(get_supported_else_val): Ditto.
	* optabs-tree.cc (target_supports_mask_load_store_p): Ditto.
	(can_vec_mask_load_store_p): Ditto.
	(target_supports_len_load_store_p): Ditto.
	(get_len_load_store_mode): Ditto.
	* optabs-tree.h (target_supports_mask_load_store_p): Ditto.
	(can_vec_mask_load_store_p): Ditto.
	* tree-vect-data-refs.cc (vect_lanes_optab_supported_p): Ditto.
	(vect_gather_scatter_fn_p): Ditto.
	(vect_check_gather_scatter): Ditto.
	(vect_load_lanes_supported): Ditto.
	* tree-vect-patterns.cc (vect_recog_gather_scatter_pattern):
	Ditto.
	* tree-vect-slp.cc (vect_get_operand_map): Adjust indices for
	else operand.
	(vect_slp_analyze_node_operations): Skip undefined else operand.
	* tree-vect-stmts.cc (exist_non_indexing_operands_for_use_p):
	Add else operand handling.
	(vect_get_vec_defs_for_operand): Handle undefined else operand.
	(check_load_store_for_partial_vectors): Add else argument.
	(vect_truncate_gather_scatter_offset): Ditto.
	(vect_use_strided_gather_scatters_p): Ditto.
	(get_group_load_store_type): Ditto.
	(get_load_store_type): Ditto.
	(vect_get_mask_load_else): Ditto.
	(vect_get_else_val_from_tree): Ditto.
	(vect_build_one_gather_load_call): Add zero else operand.
	(vectorizable_load): Use else operand.
	* tree-vectorizer.h (vect_gather_scatter_fn_p): Add else
	argument.
	(vect_load_lanes_supported): Ditto.
	(vect_get_mask_load_else): Ditto.
	(vect_get_else_val_from_tree): Ditto.

When predicating a load we implicitly assume that the else value is
zero.  This matters in case the loaded value is padded (like e.g.
a Bool) and we must ensure that the padding bytes are zero on targets
that don't implicitly zero inactive elements.

A former version of this patch still had this handling in ifcvt but
the latest version defers it to the vectorizer.

gcc/ChangeLog:

	* tree-if-conv.cc (predicate_load_or_store): Add zero else
	operand and comment.

This patch adds else-operand handling to the internal functions.

gcc/ChangeLog:

	* internal-fn.cc (add_mask_and_len_args): Rename...
	(add_mask_else_and_len_args): ...to this and add else handling.
	(expand_partial_load_optab_fn): Use adjusted function.
	(expand_partial_store_optab_fn): Ditto.
	(expand_scatter_store_optab_fn): Ditto.
	(expand_gather_load_optab_fn): Ditto.
	(internal_fn_len_index): Add else handling.
	(internal_fn_else_index): Ditto.
	(internal_fn_mask_index): Ditto.
	(get_supported_else_vals): New function.
	(supported_else_val_p): New function.
	(internal_gather_scatter_fn_supported_p): Add else operand.
	* internal-fn.h (internal_gather_scatter_fn_supported_p): Define
	else constants.
	(MASK_LOAD_ELSE_ZERO): Ditto.
	(MASK_LOAD_ELSE_M1): Ditto.
	(MASK_LOAD_ELSE_UNDEFINED): Ditto.
	(get_supported_else_vals): Declare.
	(supported_else_val_p): Ditto.

This patch amends the documentation for masked loads (maskload,
vec_mask_load_lanes, and mask_gather_load as well as their len
counterparts) with an else operand.

gcc/ChangeLog:

	* doc/md.texi: Document masked load else operand.

libgomp/ChangeLog:

	PR libgomp/117626
	* plugin/plugin-nvptx.c (nvptx_open_device): Use 'CUDA_CALL_ERET'
	with 'NULL' as error return instead of 'CUDA_CALL' that returns false.

For pointers I forgot that BIT_IOR_EXPR is not valid so when
I added the pattern to convert `max<a,b> != 0` (r15-5356), GCC
would start to ICEing saying pointer types were not valid for
BIT_IOR_EXPR.
This fixes the problem by casting to the unsigned type of the
inner type. There was another way of fixing this to handling it
as `a == 0 & b == 0` but both match and reassoication (for pointers)
will then convert it back into the form I am creating here so
let's just use that form instead.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/117646

gcc/ChangeLog:

	* match.pd (`max<a,b>==0`): Add casts to `unsigned type`.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/minmaxneeqptr-1.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

François pointed out that static_cast<__node_ptr>(&_M_before_begin) is
invalid, because _M_before_begin is only a node-base not a node.

Refactor the new merge overloads to only cast when we know we have a
valid node.

He also pointed out some optimizations to allow reusing hash codes that
might be cached in the node. The _M_src_hash_code function already has
the right logic to decide when a cached hash code can be reused by a
different _Hashtable object.

libstdc++-v3/ChangeLog:

	* include/bits/hashtable.h (_Hashtable::_M_src_hash_code):
	Improve comments.
	(_Hashtable::_M_merge_unique(_Hashtable&)): Use pointer_traits
	to get before-begin pointer. Only use static_cast on valid
	nodes, not the before-begin pointer. Reuse a hash code cached in
	the node when possible.
	(_Hashtable::_M_merge_multi(_Hashtable&)): Likewise.

Reviewed-by: François Dumont <fdumont@gcc.gnu.org>

The dependency output for header unit modules is based on the absolute
pathname of the header file, but that's not something that a makefile can
portably refer to.  This patch adds a .c++-header-unit target based on the
header name relative to an element of the include path.

libcpp/ChangeLog:

	* internal.h (_cpp_get_file_dir): Declare.
	* files.cc (_cpp_get_file_dir): New fn.
	* mkdeps.cc (make_write): Use it.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/dep-4.H: New test.

Instead of doing a dg-run with a specific target check for linux.
Use signal as the effective-target since this requires the use
of ALARM signal to do the testing.
Also use check_vect in the main and renames main to main1 to make sure
we don't use the registers.

Tested on x86_64-linux-gnu.

	PR testsuite/117494
gcc/testsuite/ChangeLog:

	* gcc.dg/vect/pr101145inf.c: Remove dg-do and replace
	with dg-require-effective-target of signal.
	* gcc.dg/vect/pr101145inf_1.c: Likewise.
	* gcc.dg/vect/pr101145inf.inc: Rename main to main1
	and mark as noinline.
	Include tree-vect.h. Have main call check_vect and main1.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

libstdc++-v3:
	* doc/xml/manual/allocator.xml: Update reference to Angelika
	Langer's article.
	* doc/html/manual/memory.html: Regenerate.

I was looking at a regression in ext-dce's behavior just before Cauldron.
Essentially a bugfix in ext-dce ended up causing us to fail to eliminate some
useless extensions.

When we have a SUBREG object with SUBREG_PROMOTED_VAR* flags set, we generally
have to be more conservative in how we process bit group liveness, making bits
live that wouldn't obviously be live otherwise.

That's not always necessary though. For example, if we're storing a promoted
subreg into memory, we may not care about those extra live bits on this
instance of the subreg object (remember subregs are not shared!).  Essentially
if the mode of the memory reference is not wider than the mode of the inner
REG, then we can clear the promoted state which in turn may allow more
extension elimination.

So at the start of ext-dce we do a simple pass over the IL and remove promoted
subreg state when it's obviously safe to do so (memory stores when the modes
allow it).  That prevents extra bits from being live and ultimately allows us
to remove more useless extensions.

The testcase is in theory generic, but many targets won't have an opportunity
to optimize this case.  So rather then build out a large inclusion/exclusion
list, I've just made the test risc-v specific.

Bootstrapped and regression tested on aarch64, riscv64, s390x, etc in my tester.

gcc/
	* ext-dce.cc (maybe_clear_subreg_promoted_p): New function.
	(ext_dce_execute): Call it.

gcc/testsuite
	* gcc.target/riscv/ext-dce-1.c: New test.

Remove stray `;;' from the middle of the introductory comment for the
"unaligned_store<mode>" expander, clearly a leftover from a previous
edition.

	gcc/
	* config/alpha/alpha.md (unaligned_store<mode>): Remove stray
	`;;'.

2024-11-17  John David Anglin  <danglin@gcc.gnu.org>

gcc/ChangeLog:

	PR target/69374
	* doc/install.texi (Specific) <hppa*-hp-hpux11>: Update anchor
	and heading to reflect removal of 32-bit hppa support on HP-UX.
	Trim 32-bit related text.

This should have been part of r15-5367.  One day I'll remember to do this
before buildbot sends me hate mail.

gcc/c-family/ChangeLog:

	* c.opt.urls: Regenerate.

In C23, bool is now a keyword.  So, doing a typedef for it is invalid.

2024-11-17  John David Anglin  <danglin@gcc.gnu.org>

libgcc/ChangeLog:

	PR target/117627
	* config/pa/linux-atomic.c: Remove typedef for bool type.

This warning covers the C23 incompibilities resulting from using
() as parameter lists in function declarations.

The warning name comes from Clang.  The implementation is not
perfect because GCC treats these two declarations as equivalent:

  void f ();
  void f (not_a_type);

This is a bit confusing because they are clearly visually distinct.
However, as of GCC 14, the second form is an error by default, so
treating both the same as far as  -Wdeprecated-non-prototype does
not seem so bad from a user experience view.

gcc/c-family/

	PR c/95445
	* c-opts.cc (c_common_post_options): Initialize
	warn_deprecated_non_prototype.
	* c.opt (Wdeprecated-non-prototype): New option.
	* c.opt.urls: Regenerate.

gcc/c/

	PR c/95445
	* c-decl.cc (start_function): Warn about parameters
	after parameter-less declaration.
	* c-typeck.cc (build_function_call_vec): Pass fntype
	to convert_arguments.
	(convert_arguments): Change argument to fntype and
	compute typelist.  Warn about parameter list mismatches
	on first parameter.

gcc/

	PR c/95445
	* doc/invoke.texi: Document -Wdeprecated-non-prototype.

gcc/testsuite/

	PR c/95445
	* gcc.dg/Wdeprecated-non-prototype-1.c: New test.
	* gcc.dg/Wdeprecated-non-prototype-2.c: New test.
	* gcc.dg/Wdeprecated-non-prototype-3.c: New test.
	* gcc.dg/Wdeprecated-non-prototype-4.c: New test.

While experimenting with testing module std I noticed that gcc -M broke on
it; it seems I need to set directives_only even sooner than I did in
r15-4219.

gcc/c-family/ChangeLog:

	* c-ppoutput.cc (preprocess_file): Don't set directives_only here.

gcc/cp/ChangeLog:

	* module.cc (module_preprocess_options): Set directives_only here.

The C++ modules code has a -fmodule-header (or -x c++-{user,system}-header)
option to specify looking up headers to compile to header units on the usual
include paths.  I'd like to have the same functionality for full C++20
modules such as module std, which I proposed to live on the include path at
bits/std.cc.  But this behavior doesn't seem necessarily connected to
modules, so I'm proposing a general C/C++ option to specify the behavior of
looking in the include path for the input files specified on the command
line.

Other ideas for the name of the option are very welcome.

The libcpp change is to allow -fsearch-include-path{,=user} to find files in
the current working directory, like -include.  This can be handy for a quick
compile of both std.cc and a file that imports it, e.g.

g++ -std=c++20 -fmodules -fsearch-include-path bits/std.cc importer.cc

gcc/ChangeLog:

	* doc/cppopts.texi: Document -fsearch-include-path.
	* doc/invoke.texi: Mention it for modules.

gcc/c-family/ChangeLog:

	* c.opt: Add -fsearch-include-path.
	* c-opts.cc (c_common_post_options): Handle it.

gcc/cp/ChangeLog:

	* module.cc (module_preprocess_options): Don't override it.

libcpp/ChangeLog:

	* internal.h (search_path_head): Declare.
	* files.cc (search_path_head): No longer static.
	* init.cc (cpp_read_main_file): Use it.

This patch introduces an installed source form of module std and std.compat.
To help a build system find them, we install a libstdc++.modules.json file
alongside libstdc++.so, which tells the build system where the files are and
any special flags it should use when compiling them (none, in this case).
The format is from a proposal in SG15.  The build system can find this file
with 'gcc -print-file-name=libstdc++.modules.json'.

It seems preferable to use a relative path from this file to the sources so
that moving the installation doesn't break the reference, but I didn't see
any obvious way to compute that without relying on coreutils, perl, or
python, so I wrote a POSIX shell script for it.  The .. canonicalization
bits aren't necessary since I discovered $(abspath), but I guess I might as
well leave them in.

Currently this installs the sources under $(gxx_include_dir)/bits/,
i.e. /usr/include/c++/15/bits.  So with my -fsearch-include-path change,
std.cc can be compiled with g++ -fsearch-include-path bits/std.cc.  Note
that if someone actually tries to #include <bits/std.cc> it will fail with
"error: module control-line cannot be in included file".

Any ideas about a more user-friendly way to express "compile module std" are
welcome.

The sources currently have the extension .cc, like other source files.

std.cc started with m.cencora's implementation in PR114600.  I've made some
adjustments, but more is probably desirable, e.g. of the <algorithm>
handling of namespace ranges, and to remove exports of templates that are
only specialized in a particular header.  I've filled in a bunch of missing
exports, and added some FIXMEs where I noticed bits that are not implemented
yet.

Since bits/stdc++.h also intends to include the whole standard library, I
include it rather than duplicate it.  But stdc++.h comments out <execution>,
due to TBB issues; I include it separately and suppress TBB usage, so module
std won't currently provide parallel execution.

It seemed most convenient for the two files to be monolithic so we don't
need to worry about include paths.  So the C library names that module
std.compat exports in both namespace std and :: are a block of code that is
appended to both files, adjusted based on whether the macro STD_COMPAT is
defined before the block.

In this implementation std.compat imports std; it would also be valid for it
to duplicate everything in std.  I see the libc++ std.compat also imports
std.

As discussed in the PR, module std is supported in C++20 mode even though it
was added in C++23.

Changes to test module std will follow in a separate patch.  In my testing
I've noticed a few compiler bugs that break various testcases, so I don't
expect to enable module std testing by default at first.

	PR libstdc++/106852

libstdc++-v3/ChangeLog:

	* include/bits/version.def: Add __cpp_lib_modules.
	* include/bits/version.h: Regenerate.
	* src/c++23/Makefile.am: Add modules std and std.compat.
	* src/c++23/Makefile.in: Regenerate.
	* src/c++23/std-clib.cc.in: New file.
	* src/c++23/std.cc.in: New file.
	* src/c++23/std.compat.cc.in: New file.
	* src/c++23/libstdc++.modules.json.in: New file.

contrib/ChangeLog:

	* relpath.sh: New file.