Repository navigation
Expand file tree
/
Copy pathfuture.tex
More file actions
1154 lines (974 loc) · 34 KB
/
Copy pathfuture.tex
File metadata and controls
1154 lines (974 loc) · 34 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
%!TEX root = std.tex
\normannex{depr}{Compatibility features}
\rSec1[depr.general]{General}
\pnum
This Annex describes features of this document
that are specified for compatibility with existing implementations.
\pnum
These are deprecated features, where
\term{deprecated}
is defined as:
Normative for the current revision of \Cpp{},
but having been identified as a candidate for removal from future revisions.
An implementation may declare library names and entities described in this Clause with the
\link{\tcode{deprecated} attribute}{dcl.attr.deprecated}.
\rSec1[depr.local]{Non-local use of TU-local entities}
\pnum
A declaration of a non-TU-local entity that is an exposure\iref{basic.link}
is deprecated.
\begin{note}
Such a declaration in an importable module unit is ill-formed.
\end{note}
\begin{example}
\begin{codeblock}
namespace {
struct A {
void f() {}
};
}
A h(); // deprecated: not internal linkage
inline void g() {A().f();} // deprecated: inline and not internal linkage
\end{codeblock}
\end{example}
\rSec1[depr.capture.this]{Implicit capture of \tcode{*this} by reference}
\pnum
For compatibility with prior revisions of \Cpp{},
a \grammarterm{lambda-expression} with \grammarterm{capture-default}
\tcode{=}\iref{expr.prim.lambda.capture} may implicitly capture
\tcode{*this} by reference.
\begin{example}
\begin{codeblock}
struct X {
int x;
void foo(int n) {
auto f = [=]() { x = n; }; // deprecated: \tcode{x} means \tcode{this->x}, not a copy thereof
auto g = [=, this]() { x = n; }; // recommended replacement
}
};
\end{codeblock}
\end{example}
\rSec1[depr.volatile.type]{Deprecated \tcode{volatile} types}
\pnum
Postfix \tcode{++} and \tcode{--} expressions\iref{expr.post.incr} and
prefix \tcode{++} and \tcode{--} expressions\iref{expr.pre.incr}
of volatile-qualified arithmetic and pointer types are deprecated.
\begin{example}
\begin{codeblock}
volatile int velociraptor;
++velociraptor; // deprecated
\end{codeblock}
\end{example}
\pnum
Certain assignments
where the left operand is a volatile-qualified non-class type
are deprecated; see~\ref{expr.assign}.
\begin{example}
\begin{codeblock}
int neck, tail;
volatile int brachiosaur;
brachiosaur = neck; // OK
tail = brachiosaur; // OK
tail = brachiosaur = neck; // deprecated
brachiosaur += neck; // OK
\end{codeblock}
\end{example}
\pnum
A function type\iref{dcl.fct}
with a parameter with volatile-qualified type or
with a volatile-qualified return type is deprecated.
\begin{example}
\begin{codeblock}
volatile struct amber jurassic(); // deprecated
void trex(volatile short left_arm, volatile short right_arm); // deprecated
void fly(volatile struct pterosaur* pteranodon); // OK
\end{codeblock}
\end{example}
\pnum
A structured binding\iref{dcl.struct.bind} of a volatile-qualified type
is deprecated.
\begin{example}
\begin{codeblock}
struct linhenykus { short forelimb; };
void park(linhenykus alvarezsauroid) {
volatile auto [what_is_this] = alvarezsauroid; // deprecated
// ...
}
\end{codeblock}
\end{example}
\rSec1[depr.ellipsis.comma]{Non-comma-separated ellipsis parameters}
A \grammarterm{parameter-declaration-clause}
of the form
\grammarterm{parameter-declaration-list} \tcode{...}
is deprecated\iref{dcl.fct}.
\begin{example}
\begin{codeblock}
void f(int...); // deprecated
void g(auto...); // OK, declares a function parameter pack
void h(auto......); // deprecated
\end{codeblock}
\end{example}
\rSec1[depr.impldec]{Implicit declaration of copy functions}
\pnum
The implicit definition of a \link{copy constructor}{class.copy.ctor}
as defaulted is deprecated if the class has
a user-declared copy assignment operator or
a user-declared \link{destructor}{class.dtor}.
The implicit definition of a \link{copy assignment operator}{class.copy.assign}
as defaulted is deprecated if the class has
a user-declared copy constructor or
a user-declared destructor.
It is possible that future versions of \Cpp{} will specify
that these implicit definitions are deleted\iref{dcl.fct.def.delete}.
\rSec1[depr.static.constexpr]{Redeclaration of \tcode{static constexpr} data members}
\pnum
For compatibility with prior revisions of \Cpp{}, a \keyword{constexpr}
static data member may be redundantly redeclared outside the class with no
initializer\iref{basic.def,class.static.data}.
This usage is deprecated.
\begin{example}
\begin{codeblock}
struct A {
static constexpr int n = 5; // definition (declaration in \CppXIV{})
};
constexpr int A::n; // redundant declaration (definition in \CppXIV{})
\end{codeblock}
\end{example}
\rSec1[depr.lit]{Literal operator function declarations using an identifier}
\pnum
A \grammarterm{literal-operator-id}\iref{over.literal} of the form
\begin{codeblock}
operator @\grammarterm{unevaluated-string}@ @\grammarterm{identifier}@
\end{codeblock}
is deprecated.
\rSec1[depr.template.template]{\tcode{template} keyword before qualified names}
\pnum
The use of the keyword \keyword{template}
before the qualified name of a class or alias template
without a template argument list is deprecated\iref{temp.names}.
\rSec1[depr.numeric.limits.has.denorm]{\tcode{has_denorm} members in \tcode{numeric_limits}}
\pnum
The following type is defined
in addition to those specified in \libheaderref{limits}:
\begin{codeblock}
namespace std {
enum @\libglobal{float_denorm_style}@ {
@\libmember{denorm_indeterminate}{float_denorm_style}@ = -1,
@\libmember{denorm_absent}{float_denorm_style}@ = 0,
@\libmember{denorm_present}{float_denorm_style}@ = 1
};
}
\end{codeblock}
\pnum
\indextext{denormalized value|see{number, subnormal}}%
\indextext{value!denormalized|see{number, subnormal}}%
\indextext{subnormal number|see{number, subnormal}}%
\indextext{number!subnormal}%
The following members are defined
in addition to those specified in \ref{numeric.limits.general}:
\begin{codeblock}
static constexpr float_denorm_style has_denorm = denorm_absent;
static constexpr bool has_denorm_loss = false;
\end{codeblock}
\pnum
The values of \tcode{has_denorm} and \tcode{has_denorm_loss} of
specializations of \tcode{numeric_limits} are unspecified.
\pnum
The following members of the specialization \tcode{numeric_limits<bool>} are defined
in addition to those specified in \ref{numeric.special}:
\indexlibrarymember{float_denorm_style}{numeric_limits}%
\indexlibrarymember{has_denorm_loss}{numeric_limits}%
\begin{codeblock}
static constexpr float_denorm_style has_denorm = denorm_absent;
static constexpr bool has_denorm_loss = false;
\end{codeblock}
\rSec1[depr.c.macros]{Deprecated C macros}
\pnum
The header \libheaderref{cfloat} has the following macros:
\begin{codeblock}
#define @\libmacro{FLT_HAS_SUBNORM}@ @\seebelow@
#define @\libmacro{DBL_HAS_SUBNORM}@ @\seebelow@
#define @\libmacro{LDBL_HAS_SUBNORM}@ @\seebelow@
#define @\libmacro{DECIMAL_DIG}@ @\seebelow@
\end{codeblock}
The header defines these macros the same as
the C standard library header \libheader{float.h}.
\xrefc{5.3.5.3.3, 7.33.6}
\pnum
In addition to being available via inclusion of the \libheader{cfloat} header,
the macros \tcode{INFINITY} and \tcode{NAN} are
available when \libheaderref{cmath} is included.
\xrefc{7.12}
\pnum
The header \libheaderref{stdbool.h} has the following macro:
\begin{codeblock}
#define @\libxmacro{bool_true_false_are_defined}@ 1
\end{codeblock}
\xrefc{7.19}
\rSec1[depr.cerrno]{Deprecated error numbers}
\pnum
The header \libheaderref{cerrno} has the following additional macros:
\begin{codeblock}
#define @\libmacro{ENODATA}@ @\seebelow@
#define @\libmacro{ENOSR}@ @\seebelow@
#define @\libmacro{ENOSTR}@ @\seebelow@
#define @\libmacro{ETIME}@ @\seebelow@
\end{codeblock}
\pnum
The meaning of these macros is defined by the POSIX standard.
\pnum
The following \tcode{enum errc} enumerators are defined
in addition to those specified in \ref{system.error.syn}:
\begin{codeblock}
@\libmember{no_message_available}{errc}@, // \tcode{ENODATA}
@\libmember{no_stream_resources}{errc}@, // \tcode{ENOSR}
@\libmember{not_a_stream}{errc}@, // \tcode{ENOSTR}
@\libmember{stream_timeout}{errc}@, // \tcode{ETIME}
\end{codeblock}
\pnum
The value of each \tcode{enum errc} enumerator above
is the same as the value of the \libheader{cerrno} macro
shown in the above synopsis.
\rSec1[depr.meta.types]{Deprecated type traits}
\pnum
The header \libheaderrefx{type_traits}{meta.type.synop}
has the following addition:
\begin{codeblock}
namespace std {
template<class T> struct is_trivial;
template<class T> constexpr bool is_trivial_v = is_trivial<T>::value;
template<class T> struct is_pod;
template<class T> constexpr bool is_pod_v = is_pod<T>::value;
template<size_t Len, size_t Align = @\exposid{default-alignment}@> // \seebelow
struct aligned_storage;
template<size_t Len, size_t Align = @\exposid{default-alignment}@> // \seebelow
using @\libglobal{aligned_storage_t}@ = aligned_storage<Len, Align>::type;
template<size_t Len, class... Types>
struct aligned_union;
template<size_t Len, class... Types>
using @\libglobal{aligned_union_t}@ = aligned_union<Len, Types...>::type;
}
\end{codeblock}
\pnum
The behavior of a program that adds specializations for
any of the templates defined in this subclause is undefined,
unless explicitly permitted by the specification of the corresponding template.
\pnum
\label{term.trivial.type}%
A \defnadj{trivial}{class} is a class that is trivially copyable and
has one or more eligible default constructors, all of which are trivial.
\begin{note}
In particular,
a trivial class does not have virtual functions or virtual base classes.
\end{note}
A \defnadj{trivial}{type} is a scalar type, a trivial class,
an array of such a type, or a cv-qualified version of one of these types.
\pnum
\indextext{POD}%
A \term{POD class} is a class that is both a trivial class and a
standard-layout class, and has no non-static data members of type non-POD class
(or array thereof). A \term{POD type} is a scalar type, a POD class, an array
of such a type, or a cv-qualified version of one of these types.
\indexlibraryglobal{is_trivial}%
\begin{itemdecl}
template<class T> struct is_trivial;
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{remove_all_extents_t<T>} shall be a complete type or \cv{} \keyword{void}.
\pnum
\remarks
\tcode{is_trivial<T>} is a \oldconcept{UnaryTypeTrait}\iref{meta.rqmts}
with a base characteristic of \tcode{true_type}
if \tcode{T} is a trivial type,
and \tcode{false_type} otherwise.
\pnum
\begin{note}
It is unspecified
whether a closure type\iref{expr.prim.lambda.closure} is a trivial type.
\end{note}
\end{itemdescr}
\indexlibraryglobal{is_pod}%
\begin{itemdecl}
template<class T> struct is_pod;
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{remove_all_extents_t<T>} shall be a complete type or \cv{} \keyword{void}.
\pnum
\remarks
\tcode{is_pod<T>} is a \oldconceptref{UnaryTypeTrait}\iref{meta.rqmts}
with a base characteristic of \tcode{true_type}
if \tcode{T} is a POD type,
and \tcode{false_type} otherwise.
\pnum
\begin{note}
It is unspecified whether a closure type\iref{expr.prim.lambda.closure} is a POD type.
\end{note}
\end{itemdescr}
\indexlibraryglobal{aligned_storage}%
\begin{itemdecl}
template<size_t Len, size_t Align = @\exposid{default-alignment}@>
struct aligned_storage;
\end{itemdecl}
\begin{itemdescr}
\pnum
The value of \exposid{default-alignment} is the most
stringent alignment requirement for any object type whose size
is no greater than \tcode{Len}\iref{basic.types}.
\pnum
\mandates
\tcode{Len} is not zero.
\tcode{Align} is equal to \tcode{alignof(T)} for some type \tcode{T} or
to \exposid{default-alignment}.
\pnum
The member typedef \tcode{type} denotes a trivial standard-layout type
suitable for use as uninitialized storage for any object
whose size is at most \tcode{Len} and
whose alignment is a divisor of \tcode{Align}.
\pnum
\begin{note}
Uses of \tcode{aligned_storage<Len, Align>::type} can be replaced
by an array \tcode{std::byte[Len]} declared with \tcode{alignas(Align)}.
\end{note}
\pnum
\begin{note}
A typical implementation would define \tcode{aligned_storage} as:
\begin{codeblock}
template<size_t Len, size_t Alignment>
struct aligned_storage {
typedef struct {
alignas(Alignment) unsigned char __data[Len];
} type;
};
\end{codeblock}
\end{note}
\end{itemdescr}
\indexlibraryglobal{aligned_union}%
\begin{itemdecl}
template<size_t Len, class... Types>
struct aligned_union;
\end{itemdecl}
\begin{itemdescr}
\pnum
\mandates
At least one type is provided.
Each type in the template parameter pack \tcode{Types}
is a complete object type.
\pnum
The member typedef \tcode{type} denotes a trivial standard-layout type
suitable for use as uninitialized storage for any object
whose type is listed in \tcode{Types};
its size shall be at least \tcode{Len}.
The static member \tcode{alignment_value}
is an integral constant of type \tcode{size_t}
whose value is the strictest alignment of all types listed in \tcode{Types}.
\end{itemdescr}
\rSec1[depr.relops]{Relational operators}%
\indexlibraryglobal{rel_ops}%
\pnum
The header \libheaderref{utility} has the following additions:
\begin{codeblock}
namespace std::rel_ops {
template<class T> bool operator!=(const T&, const T&);
template<class T> bool operator> (const T&, const T&);
template<class T> bool operator<=(const T&, const T&);
template<class T> bool operator>=(const T&, const T&);
}
\end{codeblock}
\pnum
To avoid redundant definitions of \tcode{operator!=} out of \tcode{operator==}
and operators \tcode{>}, \tcode{<=}, and \tcode{>=} out of \tcode{operator<},
the library provides the following:
\indexlibrary{\idxcode{operator"!=}}%
\begin{itemdecl}
template<class T> bool operator!=(const T& x, const T& y);
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{T} meets the \oldconcept{EqualityComparable} requirements (\tref{cpp17.equalitycomparable}).
\pnum
\returns
\tcode{!(x == y)}.
\end{itemdescr}
\indexlibraryglobal{operator>}%
\begin{itemdecl}
template<class T> bool operator>(const T& x, const T& y);
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{T} meets the \oldconcept{LessThanComparable} requirements (\tref{cpp17.lessthancomparable}).
\pnum
\returns
\tcode{y < x}.
\end{itemdescr}
\indexlibrary{\idxcode{operator<=}}%
\begin{itemdecl}
template<class T> bool operator<=(const T& x, const T& y);
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{T} meets the \oldconcept{LessThanComparable} requirements (\tref{cpp17.lessthancomparable}).
\pnum
\returns
\tcode{!(y < x)}.
\end{itemdescr}
\indexlibrary{\idxcode{operator>=}}%
\begin{itemdecl}
template<class T> bool operator>=(const T& x, const T& y);
\end{itemdecl}
\begin{itemdescr}
\pnum
\expects
\tcode{T} meets the \oldconcept{LessThanComparable} requirements (\tref{cpp17.lessthancomparable}).
\pnum
\returns
\tcode{!(x < y)}.
\end{itemdescr}
\rSec1[depr.tuple]{Tuple}
\pnum
The header \libheaderref{tuple} has the following additions:
\begin{codeblock}
namespace std {
template<class T> struct tuple_size<volatile T>;
template<class T> struct tuple_size<const volatile T>;
template<size_t I, class T> struct tuple_element<I, volatile T>;
template<size_t I, class T> struct tuple_element<I, const volatile T>;
}
\end{codeblock}
\begin{itemdecl}
template<class T> struct tuple_size<volatile T>;
template<class T> struct tuple_size<const volatile T>;
\end{itemdecl}
\begin{itemdescr}
\pnum
Let \tcode{TS} denote \tcode{tuple_size<T>} of the cv-unqualified type \tcode{T}.
If the expression \tcode{TS::value} is well-formed
when treated as an \deflink{unevaluated operand}{expr.context},
then specializations of each of the two templates meet
the \oldconceptref{TransformationTrait} requirements with a base characteristic of
\tcode{integral_constant<size_t, TS::value>}.
Otherwise, they have no member \tcode{value}.
\pnum
Access checking is performed as if
in a context unrelated to \tcode{TS} and \tcode{T}.
Only the validity of the immediate context of the expression is considered.
\pnum
In addition to being available via inclusion of the \libheaderref{tuple} header,
the two templates are available when any of the headers
\libheaderref{array},
\libheaderref{ranges}, or
\libheaderref{utility}
are included.
\end{itemdescr}
\begin{itemdecl}
template<size_t I, class T> struct tuple_element<I, volatile T>;
template<size_t I, class T> struct tuple_element<I, const volatile T>;
\end{itemdecl}
\begin{itemdescr}
\pnum
Let \tcode{TE} denote \tcode{tuple_element_t<I, T>}
of the cv-unqualified type \tcode{T}.
Then specializations of each of the two templates meet
the \oldconceptref{TransformationTrait} requirements
with a member typedef \tcode{type} that names the following type:
\begin{itemize}
\item for the first specialization, \tcode{volatile TE}, and
\item for the second specialization, \tcode{const volatile TE}.
\end{itemize}
\pnum
In addition to being available via inclusion of the \libheaderref{tuple} header,
the two templates are available when any of the headers
\libheaderref{array},
\libheaderref{ranges}, or
\libheaderref{utility}
are included.
\end{itemdescr}
\rSec1[depr.variant]{Variant}
\pnum
The header \libheaderref{variant} has the following additions:
\begin{codeblock}
namespace std {
template<class T> struct variant_size<volatile T>;
template<class T> struct variant_size<const volatile T>;
template<size_t I, class T> struct variant_alternative<I, volatile T>;
template<size_t I, class T> struct variant_alternative<I, const volatile T>;
}
\end{codeblock}
\begin{itemdecl}
template<class T> struct variant_size<volatile T>;
template<class T> struct variant_size<const volatile T>;
\end{itemdecl}
\begin{itemdescr}
\pnum
Let \tcode{VS} denote \tcode{variant_size<T>}
of the cv-unqualified type \tcode{T}.
Then specializations of each of the two templates meet
the \oldconceptref{UnaryTypeTrait} requirements
with a base characteristic of \tcode{integral_constant<size_t, VS::value>}.
\end{itemdescr}
\begin{itemdecl}
template<size_t I, class T> struct variant_alternative<I, volatile T>;
template<size_t I, class T> struct variant_alternative<I, const volatile T>;
\end{itemdecl}
\begin{itemdescr}
\pnum
Let \tcode{VA} denote \tcode{variant_alternative<I, T>}
of the cv-unqualified type \tcode{T}.
Then specializations of each of the two templates meet
the \oldconceptref{TransformationTrait} requirements
with a member typedef \tcode{type} that names the following type:
\begin{itemize}
\item for the first specialization, \tcode{volatile VA::type}, and
\item for the second specialization, \tcode{const volatile VA::type}.
\end{itemize}
\end{itemdescr}
\rSec1[depr.vector.bool.swap]{Deprecated \tcode{vector<bool, Allocator>} swap}
\pnum
The following member is declared in addition to those members specified in
\ref{vector.bool}:
\begin{codeblock}
namespace std {
template<class Allocator> class vector<bool, Allocator> {
public:
static constexpr void swap(reference x, reference y) noexcept;
};
}
\end{codeblock}
\indexlibrarymember{swap}{vector<bool>}%
\begin{itemdecl}
static constexpr void swap(reference x, reference y) noexcept;
\end{itemdecl}
\begin{itemdescr}
\pnum
\effects
Exchanges the values denoted by \tcode{x} and \tcode{y} as if by:
\begin{codeblock}
bool b = x;
x = y;
y = b;
\end{codeblock}
\end{itemdescr}
\rSec1[depr.iterator]{Deprecated \tcode{iterator} class template}
\pnum
The header \libheaderrefx{iterator}{iterator.synopsis} has the following addition:
\indexlibraryglobal{iterator}%
\begin{codeblock}
namespace std {
template<class Category, class T, class Distance = ptrdiff_t,
class Pointer = T*, class Reference = T&>
struct iterator {
using iterator_category = Category;
using value_type = T;
using difference_type = Distance;
using pointer = Pointer;
using reference = Reference;
};
}
\end{codeblock}
\pnum
The
\tcode{iterator}
template may be used as a base class to ease the definition of required types
for new iterators.
\pnum
\begin{note}
If the new iterator type is a class template, then these aliases
will not be visible from within the iterator class's template definition, but
only to callers of that class.
\end{note}
\pnum
\begin{example}
If a \Cpp{} program wants to define a bidirectional iterator for some data
structure containing \tcode{double} and such that it works on a large memory
model of the implementation, it can do so with:
\begin{codeblock}
class MyIterator :
public iterator<bidirectional_iterator_tag, double, long, T*, T&> {
// code implementing \tcode{++}, etc.
};
\end{codeblock}
\end{example}
\rSec1[depr.move.iter.elem]{Deprecated \tcode{move_iterator} access}
\pnum
The following member is declared in addition to those members
specified in \ref{move.iter.elem}:
\begin{codeblock}
namespace std {
template<class Iterator>
class move_iterator {
public:
constexpr pointer operator->() const;
};
}
\end{codeblock}
\indexlibrarymember{operator->}{move_iterator}%
\begin{itemdecl}
constexpr pointer operator->() const;
\end{itemdecl}
\begin{itemdescr}
\pnum
\returns
\tcode{current}.
\end{itemdescr}
\rSec1[depr.locale.category]{Deprecated locale category facets}
\pnum
The \tcode{ctype} locale category includes the following facets
as if they were specified
in \tref{locale.category.facets} of \ref{locale.category}.
\begin{codeblock}
codecvt<char16_t, char, mbstate_t>
codecvt<char32_t, char, mbstate_t>
codecvt<char16_t, char8_t, mbstate_t>
codecvt<char32_t, char8_t, mbstate_t>
\end{codeblock}
\pnum
The \tcode{ctype} locale category includes the following facets
as if they were specified
in \tref{locale.spec} of \ref{locale.category}.
\begin{codeblock}
codecvt_byname<char16_t, char, mbstate_t>
codecvt_byname<char32_t, char, mbstate_t>
codecvt_byname<char16_t, char8_t, mbstate_t>
codecvt_byname<char32_t, char8_t, mbstate_t>
\end{codeblock}
\pnum
The following class template specializations are required
in addition to those specified in~\ref{locale.codecvt}.
\indextext{UTF-8}%
\indextext{UTF-16}%
The specializations \tcode{codecvt<char16_t, char, mbstate_t>} and
\tcode{codecvt<char16_t, char8_t, mbstate_t>}
convert between the UTF-16 and UTF-8 encoding forms, and
\indextext{UTF-32}%
the specializations \tcode{codecvt<char32_t, char, mbstate_t>} and
\tcode{codecvt<char32_t, char8_t, mbstate_t>}
convert between the UTF-32 and UTF-8 encoding forms.
\rSec1[depr.format]{Deprecated formatting}
\rSec2[depr.format.syn]{Header \tcode{<format>} synopsis}
\pnum
The header \libheaderref{format} has the following additions:
\begin{codeblock}
namespace std {
template<class Visitor, class Context>
decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
}
\end{codeblock}
\rSec2[depr.format.arg]{Formatting arguments}
\indexlibraryglobal{visit_format_arg}%
\begin{itemdecl}
template<class Visitor, class Context>
decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
\end{itemdecl}
\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return visit(std::forward<Visitor>(vis), arg.\exposid{value_});}
\end{itemdescr}
\rSec1[depr.ctime]{Deprecated time formatting}
\pnum
The header \libheaderref{ctime} has the following additions:
\begin{codeblock}
char* asctime(const tm* timeptr);
char* ctime(const time_t* timer);
\end{codeblock}
\pnum
The functions \tcode{asctime} and \tcode{ctime}
are not required to avoid data races\iref{res.on.data.races}.
\xrefc{7.29}
\rSec1[depr.filesystems]{Deprecated file systems}
\rSec2[depr.fs.path.factory]{Deprecated filesystem path factory functions}
\pnum
The header \libheaderrefx{filesystem}{fs.filesystem.syn} has the following additions:
\indexlibraryglobal{u8path}%
\begin{itemdecl}
template<class Source>
path u8path(const Source& source);
template<class InputIterator>
path u8path(InputIterator first, InputIterator last);
\end{itemdecl}
\begin{itemdescr}
\pnum
\mandates
The value type of \tcode{Source} and \tcode{InputIterator} is
\tcode{char} or \keyword{char8_t}.
\pnum
\expects
The \tcode{source} and \range{first}{last} sequences are UTF-8 encoded.
\tcode{Source} meets the requirements specified in \ref{fs.path.req}.
\pnum
\returns
\begin{itemize}
\item If \tcode{path::value_type} is \tcode{char} and the current native
narrow encoding\iref{fs.path.type.cvt} is UTF-8,
return \tcode{path(source)} or \tcode{path(first, last)};
otherwise,
\item if \tcode{path::value_type} is \keyword{wchar_t} and the
native wide encoding is UTF-16, or
if \tcode{path::value_type} is \keyword{char16_t} or \keyword{char32_t},
convert \tcode{source} or \range{first}{last}
to a temporary, \tcode{tmp}, of type \tcode{path::string_type} and
return \tcode{path(tmp)};
otherwise,
\item convert \tcode{source} or \range{first}{last}
to a temporary, \tcode{tmp}, of type \tcode{u32string} and
return \tcode{path(tmp)}.
\end{itemize}
\pnum
\remarks
Argument format conversion\iref{fs.path.fmt.cvt} applies to the
arguments for these functions. How Unicode encoding conversions are performed is
unspecified.
\pnum
\begin{example}
A string is to be read from a database that is encoded in UTF-8, and used
to create a directory using the native encoding for filenames:
\begin{codeblock}
namespace fs = std::filesystem;
std::string utf8_string = read_utf8_data();
fs::create_directory(fs::u8path(utf8_string));
\end{codeblock}
For POSIX-based operating systems with the native narrow encoding set
to UTF-8, no encoding or type conversion occurs.
For POSIX-based operating systems with the native narrow encoding not
set to UTF-8, a conversion to UTF-32 occurs, followed by a conversion to the
current native narrow encoding. Some Unicode characters may have no native character
set representation.
For Windows-based operating systems a conversion from UTF-8 to
UTF-16 occurs.
\end{example}
\begin{note}
The example above is representative of
a historical use of \tcode{filesystem::u8path}.
To indicate a UTF-8 encoding,
passing a \tcode{std::u8string} to \tcode{path}'s constructor is preferred
as it is consistent with \tcode{path}'s handling of other encodings.
\end{note}
\end{itemdescr}
\rSec2[depr.fs.path.obs]{Deprecated filesystem path format observers}
\indexlibraryglobal{path}%
\pnum
The following members are declared in addition to those members
specified in \ref{fs.path.member}:
\begin{codeblock}
namespace std::filesystem {
class path {
public:
std::string string() const;
std::string generic_string() const;
};
}
\end{codeblock}
\indexlibrarymember{string}{path}%
\begin{itemdecl}
std::string string() const;
\end{itemdecl}
\begin{itemdescr}
\pnum
\returns
\tcode{native_encoded_string()}.
\end{itemdescr}
\indexlibrarymember{generic_string}{path}%
\begin{itemdecl}
std::string generic_string() const;
\end{itemdecl}
\begin{itemdescr}
\pnum
\returns
\tcode{generic_native_encoded_string()}.
\end{itemdescr}
\rSec1[depr.atomics]{Deprecated atomic operations}
\rSec2[depr.atomics.general]{General}
\pnum
The header \libheaderrefx{atomic}{atomics.syn} has the following additions.
\begin{codeblock}
namespace std {
template<class T>
void atomic_init(volatile atomic<T>*, typename atomic<T>::value_type) noexcept;
template<class T>
void atomic_init(atomic<T>*, typename atomic<T>::value_type) noexcept;
template<class T>
constexpr T kill_dependency(T y) noexcept; // freestanding
inline constexpr memory_order memory_order_consume = memory_order::consume; // freestanding
#define @\libmacro{ATOMIC_VAR_INIT}@(value) @\seebelow@
}
\end{codeblock}
\rSec2[depr.atomics.volatile]{Volatile access}
\pnum
If an \tcode{atomic}\iref{atomics.types.generic} specialization has one of the following overloads,
then that overload participates in overload resolution
even if \tcode{atomic<T>::is_always_lock_free} is \tcode{false}:
\begin{codeblock}
void store(T desired, memory_order order = memory_order::seq_cst) volatile noexcept;
T operator=(T desired) volatile noexcept;
T load(memory_order order = memory_order::seq_cst) const volatile noexcept;
operator T() const volatile noexcept;
T exchange(T desired, memory_order order = memory_order::seq_cst) volatile noexcept;
bool compare_exchange_weak(T& expected, T desired,
memory_order success, memory_order failure) volatile noexcept;
bool compare_exchange_strong(T& expected, T desired,
memory_order success, memory_order failure) volatile noexcept;
bool compare_exchange_weak(T& expected, T desired,
memory_order order = memory_order::seq_cst) volatile noexcept;
bool compare_exchange_strong(T& expected, T desired,
memory_order order = memory_order::seq_cst) volatile noexcept;
T fetch_@\placeholdernc{key}@(T operand, memory_order order = memory_order::seq_cst) volatile noexcept;
T operator @\placeholdernc{op}@=(T operand) volatile noexcept;
T* fetch_@\placeholdernc{key}@(ptrdiff_t operand, memory_order order = memory_order::seq_cst) volatile noexcept;
value_type operator++(int) volatile noexcept;
value_type operator--(int) volatile noexcept;
value_type operator++() volatile noexcept;
value_type operator--() volatile noexcept;
void wait(T old, memory_order order = memory_order::seq_cst) const volatile noexcept;
void notify_one() volatile noexcept;
void notify_all() volatile noexcept;
\end{codeblock}
\rSec2[depr.atomics.nonmembers]{Non-member functions}
\indexlibraryglobal{atomic_init}%
\begin{itemdecl}
template<class T>
void atomic_init(volatile atomic<T>* object, typename atomic<T>::value_type desired) noexcept;
template<class T>
void atomic_init(atomic<T>* object, typename atomic<T>::value_type desired) noexcept;
\end{itemdecl}
\begin{itemdescr}
\pnum
\effects