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Implement LWG-4037 Static data members of ctype_base are not yet required to be usable in constant expressions #6079

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Implement LWG-4037 Static data members of ctype_base are not yet required to be usable in constant expressions #6079

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38 changes: 21 additions & 17 deletions stl/inc/xlocale
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Original file line number Diff line number Diff line change
Expand Up @@ -2369,25 +2369,29 @@ _STL_RESTORE_DEPRECATED_WARNING
#define _UP _UPPER // 'A'-'Z'
#define _XD _HEX // '0'-'9', 'A'-'F', 'a'-'f'

_EXPORT_STD extern "C++" struct _CRTIMP2_PURE_IMPORT ctype_base // base for ctype
: locale::facet // TRANSITION, ABI, shouldn't be derived from locale::facet
{
enum { // constants for character classifications
alnum = _DI | _LO | _UP | _XA,
alpha = _LO | _UP | _XA,
cntrl = _BB,
digit = _DI,
graph = _DI | _LO | _PU | _UP | _XA,
lower = _LO,
print = _DI | _LO | _PU | _SP | _UP | _XA | _XD,
punct = _PU,
space = _CN | _SP,
upper = _UP,
xdigit = _XD,
blank = _CN | _SP
};
struct _Ctype_constants_base {
using mask = short; // to match <ctype.h>

// constants for character classifications

static constexpr mask alnum = _DI | _LO | _UP | _XA;
static constexpr mask alpha = _LO | _UP | _XA;
static constexpr mask cntrl = _BB;
static constexpr mask digit = _DI;
static constexpr mask graph = _DI | _LO | _PU | _UP | _XA;
static constexpr mask lower = _LO;
static constexpr mask print = _DI | _LO | _PU | _SP | _UP | _XA | _XD;
static constexpr mask punct = _PU;
static constexpr mask space = _CN | _SP;
static constexpr mask upper = _UP;
static constexpr mask xdigit = _XD;
static constexpr mask blank = _CN | _SP;
};

_EXPORT_STD extern "C++" struct _CRTIMP2_PURE_IMPORT ctype_base // base for ctype
: locale::facet, // TRANSITION, ABI, shouldn't be derived from locale::facet
_Ctype_constants_base // TRANSITION, ABI, avoid affecting DLL interface
{
__CLR_OR_THIS_CALL ctype_base(size_t _Refs = 0) noexcept // strengthened
: locale::facet(_Refs) {}

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34 changes: 34 additions & 0 deletions tests/std/tests/Dev11_1074023_constexpr/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -801,6 +801,12 @@ void test_all_constants() {

test_constants<ios_base::seekdir, ios_base::beg, ios_base::cur, ios_base::end>();

// LWG-4037 "Static data members of ctype_base are not yet required to be usable in constant expressions"
// The following furtherly requires ctype_base::mask to be usable as a type of a constant template parameter.
test_constants<ctype_base::mask, ctype_base::alnum, ctype_base::alpha, ctype_base::cntrl, ctype_base::digit,
ctype_base::graph, ctype_base::lower, ctype_base::print, ctype_base::punct, ctype_base::space,
ctype_base::upper, ctype_base::xdigit, ctype_base::blank>();

test_constants<RC::syntax_option_type, RC::icase, RC::nosubs, RC::optimize, RC::collate, RC::ECMAScript, RC::basic,
RC::extended, RC::awk, RC::grep, RC::egrep, regex::icase, regex::nosubs, regex::optimize, regex::collate,
regex::ECMAScript, regex::basic, regex::extended, regex::awk, regex::grep, regex::egrep>();
Expand All @@ -814,6 +820,34 @@ void test_all_constants() {
RC::error_badrepeat, RC::error_complexity, RC::error_stack>();
}

// Ensure that these members of ctype_base are actually implemented as static const members of the correct type.

STATIC_ASSERT(is_same_v<decltype(ctype_base::alnum), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::alpha), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::cntrl), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::digit), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::graph), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::lower), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::print), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::punct), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::space), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::upper), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::xdigit), const ctype_base::mask>);
STATIC_ASSERT(is_same_v<decltype(ctype_base::blank), const ctype_base::mask>);

STATIC_ASSERT(is_same_v<decltype((ctype_base::alnum)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::alpha)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::cntrl)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::digit)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::graph)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::lower)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::print)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::punct)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::space)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::upper)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::xdigit)), const ctype_base::mask&>);
STATIC_ASSERT(is_same_v<decltype((ctype_base::blank)), const ctype_base::mask&>);

constexpr csub_match sm{};
STATIC_ASSERT(sm.first == nullptr);
STATIC_ASSERT(sm.second == nullptr);
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