23 C++ Implementation-Defined Behavior

Table 23-1. Implementation-Defined Behavior
ISO Standard	Implementation
Which of the compiler's output messages are diagnostic messages (1.3.6)
	All output to `stderr` is a diagnostic.
The required libraries for a freestanding implementation (1.4)
	See the response for The set of headers for a freestanding implementation (17.6.1.3).
The number of bits in a byte (1.7)
	8 bits
What constitutes an interactive device (1.9)
	If `isatty()` is true, then interactive stream support is implied.
The number of threads in a program under a freestanding implementation (1.10)
	Threads are not directly supported.
How physical source file characters are mapped to the basic source character set (2.2)
	The locale settings determine the default source character set or UTF-8 if this cannot be determined by the locale. The basic source character set is UTF-8.
Physical source file characters (2.2)
	Defaults to the set locale and if that doesn’t work, defaults to UTF-8. Can be any encoding supported by the system’s `iconv()` library routine.
The execution character member chosen for a source character that does not map to an equivalent execution character. (2.2)
	ABI Defined
Whether source of translation units must be available to locate template definitions (2.2)
	The source must be available.
The execution character-set and execution wide-character set (2.3)
	The execution character set contains [`a-zA-Z0-9_{}[]#()<>%:;.?*+-/^&\|∼!=,\"’`], space, control characters representing horizontal tab, vertical tab, form feed, new-line, alert, backspace, carriage return, and a null character. The execution wide-character set is the same, except instead of a null character it has a null wide character. Encoding can be anything supported by the system’s `iconv()` library routine, defaulting to UTF-8 (or UTF-32, for the wide-character set).
The mapping header name to header or external source file (2.9)
	Same name as the header, in UTF-8.
The encoding of universal character name not in the execution character set (2.14.3)
	`\UNNNNNNNN` or `\uNNNN`, where `N` is a hex-quad, corresponding to the character short name in ISO/IEC 10646 `NNNNNNNN` or `0000NNNN`, respectively.
The semantics of non-standard escape sequences (2.14.3)
	As an extension, GCC supports the sequence `'\e'` to act as the ASCII `ESC` character.
The value of a character literal outside the range of the corresponding type (2.14.3)
	The last byte of the series of bytes making up the literal.
The wide-character literal with single c-char that is not in execution wide-character set (2.14.3)
	The last four bytes of the series of bytes making up the literal.
The choice of a larger or smaller value of floating literal when the value is not in the range of representable values for its type (2.14.4)
	As per Annex F of C99.
The concatenation of string literals other than those fully specified by the standard (2.14.5)
	No extra concatenations are supported.
Whether all string literals are distinct (that is, are stored in non-overlapping objects) (2.14.5)
	String literals are not necessarily distinct.
The linkage of `main()` (3.6.1)
	External linkage.
The parameters to main (3.6.1)
	`int main(void)` or `int main(int argc, char** argv)`
What constitutes start-up and termination in freestanding environment (3.6.1)
	Determined by the device-specific startup code. The default code shipped in a DFP calls constructors before `main()` for objects of namespace scope with static storage duration but does not call destructors after return from `main()`.
Whether defining main is required in a freestanding environment (3.6.1)
	Yes - The device-specific startup code can be customized to not call `main()`, but some features such as the stack-usage report require `main()`.
Whether dynamic initialization of a non-local variable with static or thread storage duration is done before the first statement of the initial function of the thread (3.6.2)
	Threads are not directly supported.
Whether dynamic initialization of a non-local variable with static storage duration is done before the first statement of `main()` (3.6.2)
	Determined by the device-specific startup code, but the default startup code provided in a DFP does call the constructors.
Whether an implementation has relaxed or strict pointer safety (3.7.4.3)
	Relaxed pointer safety.
The extended signed integer types (3.9.1)
	None
The representation of `char` (3.9.1)
	One byte.
The signedness of a plain `char` (3.9.1)
	A plain `char` is unsigned.
The value representation of floating-point types (3.9.1)
	IEEE-754
The value representation of pointer types (3.9.2)
	32 bits.
The number of bytes between successive addresses at which a given object can be allocated alignment (3.11)
	Valid alignments are powers of 2 up to and including 2²⁸.
Whether any extended object alignments are supported and the contexts in which they are supported (3.11)
	Extended alignments up to 2²⁸ are allowed, subject to the device memory layout.
The value of the result of unsigned to signed conversion (4.7)
	For conversion to a type of width N, the value is reduced modulo 2^N to be within range of the type.
The result of an inexact floating-point conversion (4.8)
	Software emulation uses Round to Nearest but the mode can be changed when using a hardware FPU.
The value of result of inexact integer to floating-point conversions (4.9)
	As per C99 Annex F.
The rank of extended signed integer type (4.13)
	Extended signed integer types are not supported.
Passing an argument of class type through ellipsis (5.2.2)
	Supported
The class publicly derived from `std::type_info` which can be returned by `typeid` (5.2.8)
	No extra class is defined. The result is `std::type_info`.
The conversions between pointers and integers (5.2.10)
	A cast from an integer to a pointer or vice versa uses the binary representation of the source type, reinterpreted as appropriate for the destination type. If the source type is larger than the destination type, the Most Significant bits are discarded. When casting from a pointer to an integer, if the source type is smaller than the destination type, the result is sign extended. When casting from an integer to a pointer, if the source type is smaller than the destination type, the result is extended based on the signedness of the source type.
The meaning of converting a function pointer to an object pointer type or vice versa (5.2.10)
	Conversion is supported. The binary representation is preserved.
The result of `sizeof` when applied to fundamental types other than `char`, `signed char`, and `unsigned char` (5.3.3)
	See 9.2 Integer Data Types, noting that `sizeof()` returns a size in bytes.
Whether over-aligned types are supported (5.3.4, 20.7.9.1, 20.7.11)
	Yes.
The type of `ptrdiff_t` (5.7, 18.2)
	`int`
The result of a right shift of negative values (5.8)
	Bitwise operators act on the representation of the value including both the sign and value bits, where the sign bit is considered immediately above the highest-value value bit.
The meaning of `attribute` declaration (7)
	See 9.10 Variable Attributes, 14.1.2 Function Attributes and 14.1.1 Function Specifiers.
The underlying type for enumeration (7.2)
	If the enumeration values are all non-negative, the type is `unsigned int`, else it is `int`.
The meaning of the `asm` declaration (7.4)
	See 17.2 Using Inline Assembly Language.
The semantics of linkage specifiers (7.5)
	Only “C” and “C++” linkage are supported.
The behavior of non-standard attributes (7.6.1)
	See 9.10 Variable Attributes, 14.1.2 Function Attributes and 14.1.1 Function Specifiers.
The behavior of an attribute-scoped-token (7.6.1)
	Attributes are available in the “gnu” namespace and are equivalent to `__attribute__`.
The string resulting from `__func__` (8.4.1)
	Treated as a constant expression and can be used in constexpr contexts. The string contains the function name only.
The allocation of bit-fields within a class object (9.6)
	Bit fields are allocated left to right.
The alignment of bit-fields within a class object (9.6)
	Each member is located to the lowest available offset allowable according to the alignment restrictions of the member type.
The semantics of linkage specification on templates (14)
	Only `"C"` and `"C++"` linkage are supported.
Whether the stack is unwound before a call to `std::terminate()` (15.3, 15.5.1)
	The stack is not unwound.
Whether the stack is unwound before calling `std::terminate()` when a `noexcept` specification is violated (15.5.1)
	The stack is not unwound.
The numeric values of character literals in `#if` directives (16.1)
	Interpreted in the same manner as they would on the target.
Whether a single-character character literal may have a negative value (16.1)
	No
The manner of search for included source files (16.2)
	Sequential, through a defined list of search paths. The search ends on the first match.
The nesting limit for `#include` directives (16.2)
	XC-DSC imposes a limit of 200 levels to avoid runaway recursion.
The search locations for headers included using `""` (16.2)
	The `#include "file"` directive is used for header files defined by your project. XC-DSC searches for the file in the directory containing the current source file, then in the quote directories, and then in the system directories. You can prepend directories using a command-line option.
The search locations for headers included using `<>` (16.2)
	The `#include <file>` directive is used for system header files packaged with XC-DSC. You can prepend search directories using a command-line option. Directories are searched in the following order: `pic32c/include/CMSIS/Core/Include pic32c/include_mcc pic32c/include/c++/<gcc-ver> pic32c/include/c++/<gcc-ver>/pic32c/<isa-arch-ver>/nofp pic32c/include/c++/<gcc-ver>/backward pic32c/include pic32c/include/musl lib/gcc/pic32c/<gcc-ver>/include`
The sequence of places searched for a header (16.2)
	Quote form includes search the directory of the current file, then in the system directories. Angle-bracket form includes only search the system directories.
The behavior of a `#pragma` directive (16.6)
	See 22.13 Preprocessing Directives (ISO 6.8.6).
The text equated to `__DATE__` when date of translation is not available (16.8)
	Expands to `"??? ?? ????"`
The text equated to `__TIME__` when time of translation is not available (16.8)
	Expands to `"??? ?? ????"`
Whether `__STDC_VERSION__` is a predefined macro and what it means (16.8)
	This macro is a long integer constant that has the format `yyyymmL`, where `yyyy` is the year and `mm` is the month of the C Standard version with which the compiler is compatible. This shows the C Standard version to which the compiler conforms.
Whether `__STDC__` is a predefined macro and what it means (16.8)
	In normal operation, this macro expands to the constant 1, to signify that this compiler conforms to ISO Standard C.
The set of headers for a freestanding implementation (17.6.1.3)
	Every header required by the standard except `<atomic>`, those being: `<ciso646> <cstddef> <cfloat> <limits> <climits> <cstdint> <cstdlib> <new> <typeinfo> <exception> <initializer_list> <cstdalign> <cstdarg> <cstdbool> <type_traits>`
Whether a name from the C standard library declared with external linkage has `extern "C"` or `extern "C++"` linkage (17.6.2.3)
	`extern "C++"`
The exceptions thrown by standard library functions that do not have an exception specification (17.6.5.12)
	There are no implementation-defined exception classes.
The `error_category` for errors originating outside the operating system (17.6.5.14)
	None.
The type of `size_t` (18.2)
	`unsigned int`
The form of the exit status returned to the host environment (18.5)
	Host environments are not supported.
The return value of `bad_alloc::what` (18.6.2.1)
	The name of the class.
The return value of `type_info::name()` (18.7.1)
	The mangled type name.
The return value of `bad_cast::what` (18.7.2)
	The name of the class.
The return value of `bad_typeid::what` (18.7.3)
	The name of the class.
The result of `exception::what` (18.8.1)
	The name of the class.
The return value of `bad_exception::what` (18.8.2)
	The name of the class.
The use of a non-POF (non-“plain old function”) as signal handler (18.10)
	Signals are not supported.
The exception type when the `shared_ptr` constructor fails (20.8.2.2.1)
	`std::bad_alloc`
Whether placeholder types are `CopyAssignable` (20.9.9.1.4)
	Yes.
Whether extended alignment is supported (20.10.7.6)
	Yes.
Whether values are rounded or truncated to the required precision when converting between `time_t` values and `time_point` objects (20.12.7.1)
	Values are truncated.
The type of `streamoff` (21.2.3.1)
	`long long`
The type of `streampos` (21.2.3.1)
	Synonym for `fpos<mbstate_t>`
The return value of `char_traits<char16_t>::eof` (21.2.3.2)
	`int_type(-1)`
The type of `u16streampos` (21.2.3.2)
	Synonym for `fpos<mbstate_t>`
The return value of `char_traits<char32_t>::eof` (21.2.3.3)
	`int_type(-1)`
The type of `u32streampos` (21.2.3.3)
	Synonym for `fpos<mbstate_t>`
The type of `wstreampos` (21.2.3.4)
	Synonym for `fpos<mbstate_t>`
Whether locale object is global or per-thread (22.3.1)
	Locale object is global.
The effect on C locale of calling `locale::global` (22.3.1.5)
	If the locale has a name, same as `setlocale()`.
The value of `ctype<char>::table_size` (22.4.1.3)
	`SCHAR_MAX + 1`
The additional formats accepted for `time_get::do_get_date` (22.4.5.1.2)
	None
Whether `time_get::do_get_year` accepts two-digit year numbers (22.4.5.1.2)
	Two-digit year numbers are accepted.
The formatted character sequence generated by `time_put::do_put` in the C locale (22.4.5.3.2)
	Same as `strftime()`
The type of `array::const_iterator` (23.3.2.1)
	`const T*`
The type of `array::iterator` (23.3.2.1)
	`T*`
The default number of buckets in `unordered_map` when this is not specified with the constructor (23.5.4.2)
	0
The default number of buckets in `unordered_multimap` when this is not specified with the constructor (23.5.5.2)
	0
The default number of buckets in `unordered_set` when this is not specified with the constructor (23.5.6.2)
	0
The default number of buckets in `unordered_multiset` when this is not specified with the constructor (23.5.7.2)
	0
The underlying source of random numbers for `random_shuffle` (25.3.12)
	It uses `rand()` as the source of randomness.
The effect of calling `ios_base::sync_with_stdio` after any input or output operation on standard streams (27.5.3.4)
	The synchronization referred to is only that between the standard C facilities and the standard C++ objects. User-declared streams are unaffected.
The argument values used to construct the `fail` object of `basic_ios::failure` thrown by `basic_ios` flags functions (27.5.5.4)
	`const char&`
Whether sequence pointers are copied by `basic_stringbuf` move constructor (27.8.2.1)
	Sequence pointers are copied.
The effect of calling `basic_streambuf::setbuf` with non-zero arguments (27.8.2.4)
	If no buffer has already been created, and both arguments are non-zero, then the first argument is used as a buffer.
Whether sequence pointers are copied by `basic_filebuf` move constructor (27.9.1.2)
	Sequence pointers are copied.
The effect of calling `basic_filebuf::setbuf` with non-zero arguments (27.9.1.5)
	The first argument is used as a buffer.
The effect of calling `basic_filebuf::sync` when a get area exists (27.9.1.5)
	No effect.
The type of `regex_constants::error_type` (28.5.3)
	Unscoped enumeration types.
The values of various `ATOMIC_..._LOCK_FREE` macros (29.4)
	Not supported.
Whether `get_pointer_safety` returns `pointer_safety::relaxed` or `pointer_safety::preferred` if the implementation has relaxed pointer safety (29.4)
	Relaxed pointer safety.
The presence and meaning of `native_handle_type` and `native_handle` (30.2.3)
	Native handles are not supported.
The type of `ios_base::streamoff` (D.6)
	`long long int`
The type of `ios_base::streampos` (D.6)
	Typedef `fpos<mbstate_t>`

Which of the compiler's output messages are diagnostic messages (1.3.6)

All output to stderr is a diagnostic.

The required libraries for a freestanding implementation (1.4)

See the response for The set of headers for a freestanding implementation (17.6.1.3).

The number of bits in a byte (1.7)

8 bits

What constitutes an interactive device (1.9)

If isatty() is true, then interactive stream support is implied.

The number of threads in a program under a freestanding implementation (1.10)

Threads are not directly supported.

How physical source file characters are mapped to the basic source character set (2.2)

The locale settings determine the default source character set or UTF-8 if this cannot be determined by the locale. The basic source character set is UTF-8.

Physical source file characters (2.2)

Defaults to the set locale and if that doesn’t work, defaults to UTF-8. Can be any encoding supported by the system’s iconv() library routine.

The execution character member chosen for a source character that does not map to an equivalent execution character. (2.2)

ABI Defined

Whether source of translation units must be available to locate template definitions (2.2)

The source must be available.

The execution character-set and execution wide-character set (2.3)

The execution character set contains [a-zA-Z0-9_{}[]#()<>%:;.?*+-/^&|∼!=,\"’], space, control characters representing horizontal tab, vertical tab, form feed, new-line, alert, backspace, carriage return, and a null character. The execution wide-character set is the same, except instead of a null character it has a null wide character. Encoding can be anything supported by the system’s iconv() library routine, defaulting to UTF-8 (or UTF-32, for the wide-character set).

The mapping header name to header or external source file (2.9)

Same name as the header, in UTF-8.

The encoding of universal character name not in the execution character set (2.14.3)

\UNNNNNNNN or \uNNNN, where N is a hex-quad, corresponding to the character short name in ISO/IEC 10646 NNNNNNNN or 0000NNNN, respectively.

The semantics of non-standard escape sequences (2.14.3)

As an extension, GCC supports the sequence '\e' to act as the ASCII ESC character.

The value of a character literal outside the range of the corresponding type (2.14.3)

The last byte of the series of bytes making up the literal.

The wide-character literal with single c-char that is not in execution wide-character set (2.14.3)

The last four bytes of the series of bytes making up the literal.

The choice of a larger or smaller value of floating literal when the value is not in the range of representable values for its type (2.14.4)

As per Annex F of C99.

The concatenation of string literals other than those fully specified by the standard (2.14.5)

No extra concatenations are supported.

Whether all string literals are distinct (that is, are stored in non-overlapping objects) (2.14.5)

String literals are not necessarily distinct.

The linkage of main() (3.6.1)

External linkage.

The parameters to main (3.6.1)

int main(void)

or

int main(int argc, char** argv)

What constitutes start-up and termination in freestanding environment (3.6.1)

Determined by the device-specific startup code. The default code shipped in a DFP calls constructors before main() for objects of namespace scope with static storage duration but does not call destructors after return from main().

Whether defining main is required in a freestanding environment (3.6.1)

Yes - The device-specific startup code can be customized to not call main(), but some features such as the stack-usage report require main().

Whether dynamic initialization of a non-local variable with static or thread storage duration is done before the first statement of the initial function of the thread (3.6.2)

Threads are not directly supported.

Whether dynamic initialization of a non-local variable with static storage duration is done before the first statement of main() (3.6.2)

Determined by the device-specific startup code, but the default startup code provided in a DFP does call the constructors.

Whether an implementation has relaxed or strict pointer safety (3.7.4.3)

Relaxed pointer safety.

The extended signed integer types (3.9.1)

None

The representation of char (3.9.1)

One byte.

The signedness of a plain char (3.9.1)

A plain char is unsigned.

The value representation of floating-point types (3.9.1)

IEEE-754

The value representation of pointer types (3.9.2)

32 bits.

The number of bytes between successive addresses at which a given object can be allocated alignment (3.11)

Valid alignments are powers of 2 up to and including 2²⁸.

Whether any extended object alignments are supported and the contexts in which they are supported (3.11)

Extended alignments up to 2²⁸ are allowed, subject to the device memory layout.

The value of the result of unsigned to signed conversion (4.7)

For conversion to a type of width N, the value is reduced modulo 2^N to be within range of the type.

The result of an inexact floating-point conversion (4.8)

Software emulation uses Round to Nearest but the mode can be changed when using a hardware FPU.

The value of result of inexact integer to floating-point conversions (4.9)

As per C99 Annex F.

The rank of extended signed integer type (4.13)

Extended signed integer types are not supported.

Passing an argument of class type through ellipsis (5.2.2)

Supported

The class publicly derived from std::type_info which can be returned by typeid (5.2.8)

No extra class is defined. The result is std::type_info.

The conversions between pointers and integers (5.2.10)

A cast from an integer to a pointer or vice versa uses the binary representation of the source type, reinterpreted as appropriate for the destination type.

If the source type is larger than the destination type, the Most Significant bits are discarded. When casting from a pointer to an integer, if the source type is smaller than the destination type, the result is sign extended. When casting from an integer to a pointer, if the source type is smaller than the destination type, the result is extended based on the signedness of the source type.

The meaning of converting a function pointer to an object pointer type or vice versa (5.2.10)

Conversion is supported. The binary representation is preserved.

The result of sizeof when applied to fundamental types other than char,

signed
                                                  char

, and unsigned char (5.3.3)

See 9.2 Integer Data Types, noting that sizeof() returns a size in bytes.

Whether over-aligned types are supported (5.3.4, 20.7.9.1, 20.7.11)

Yes.

The type of ptrdiff_t (5.7, 18.2)

int

The result of a right shift of negative values (5.8)

Bitwise operators act on the representation of the value including both the sign and value bits, where the sign bit is considered immediately above the highest-value value bit.

The meaning of attribute declaration (7)

See 9.10 Variable Attributes, 14.1.2 Function Attributes and 14.1.1 Function Specifiers.

The underlying type for enumeration (7.2)

If the enumeration values are all non-negative, the type is

unsigned
                                                  int

, else it is int.

The meaning of the asm declaration (7.4)

See 17.2 Using Inline Assembly Language.

The semantics of linkage specifiers (7.5)

Only “C” and “C++” linkage are supported.

The behavior of non-standard attributes (7.6.1)

See 9.10 Variable Attributes, 14.1.2 Function Attributes and 14.1.1 Function Specifiers.

The behavior of an attribute-scoped-token (7.6.1)

Attributes are available in the “gnu” namespace and are equivalent to __attribute__.

The string resulting from __func__ (8.4.1)

Treated as a constant expression and can be used in constexpr contexts. The string contains the function name only.

The allocation of bit-fields within a class object (9.6)

Bit fields are allocated left to right.

The alignment of bit-fields within a class object (9.6)

Each member is located to the lowest available offset allowable according to the alignment restrictions of the member type.

The semantics of linkage specification on templates (14)

Only "C" and "C++" linkage are supported.

Whether the stack is unwound before a call to std::terminate() (15.3, 15.5.1)

The stack is not unwound.

Whether the stack is unwound before calling std::terminate() when a noexcept specification is violated (15.5.1)

The stack is not unwound.

The numeric values of character literals in #if directives (16.1)

Interpreted in the same manner as they would on the target.

Whether a single-character character literal may have a negative value (16.1)

No

The manner of search for included source files (16.2)

Sequential, through a defined list of search paths. The search ends on the first match.

The nesting limit for #include directives (16.2)

XC-DSC imposes a limit of 200 levels to avoid runaway recursion.

The search locations for headers included using "" (16.2)

The

#include
                                                "file"

directive is used for header files defined by your project. XC-DSC searches for the file in the directory containing the current source file, then in the quote directories, and then in the system directories. You can prepend directories using a command-line option.

The search locations for headers included using <> (16.2)

The

#include
                                                  <file>

directive is used for system header files packaged with XC-DSC. You can prepend search directories using a command-line option. Directories are searched in the following order:

pic32c/include/CMSIS/Core/Include 
pic32c/include_mcc 
pic32c/include/c++/<gcc-ver> 
pic32c/include/c++/<gcc-ver>/pic32c/<isa-arch-ver>/nofp 
pic32c/include/c++/<gcc-ver>/backward 
pic32c/include 
pic32c/include/musl 
lib/gcc/pic32c/<gcc-ver>/include

The sequence of places searched for a header (16.2)

Quote form includes search the directory of the current file, then in the system directories. Angle-bracket form includes only search the system directories.

The behavior of a #pragma directive (16.6)

See 22.13 Preprocessing Directives (ISO 6.8.6).

The text equated to __DATE__ when date of translation is not available (16.8)

Expands to

"??? ??
                                                  ????"

The text equated to __TIME__ when time of translation is not available (16.8)

Expands to

"??? ??
                                                  ????"

Whether __STDC_VERSION__ is a predefined macro and what it means (16.8)

This macro is a long integer constant that has the format yyyymmL, where yyyy is the year and mm is the month of the C Standard version with which the compiler is compatible. This shows the C Standard version to which the compiler conforms.

Whether __STDC__ is a predefined macro and what it means (16.8)

In normal operation, this macro expands to the constant 1, to signify that this compiler conforms to ISO Standard C.

The set of headers for a freestanding implementation (17.6.1.3)

Every header required by the standard except <atomic>, those being:

<ciso646>
<cstddef>
<cfloat>
<limits>
<climits>
<cstdint>
<cstdlib>
<new>
<typeinfo>
<exception>
<initializer_list>
<cstdalign>
<cstdarg>
<cstdbool>
<type_traits>

Whether a name from the C standard library declared with external linkage has extern "C" or

extern
                                                "C++"

linkage (17.6.2.3)

extern "C++"

The exceptions thrown by standard library functions that do not have an exception specification (17.6.5.12)

There are no implementation-defined exception classes.

The error_category for errors originating outside the operating system (17.6.5.14)

None.

The type of size_t (18.2)

unsigned int

The form of the exit status returned to the host environment (18.5)

Host environments are not supported.

The return value of bad_alloc::what (18.6.2.1)

The name of the class.

The return value of type_info::name() (18.7.1)

The mangled type name.

The return value of bad_cast::what (18.7.2)

The name of the class.

The return value of bad_typeid::what (18.7.3)

The name of the class.

The result of exception::what (18.8.1)

The name of the class.

The return value of bad_exception::what (18.8.2)

The name of the class.

The use of a non-POF (non-“plain old function”) as signal handler (18.10)

Signals are not supported.

The exception type when the shared_ptr constructor fails (20.8.2.2.1)

std::bad_alloc

Whether placeholder types are CopyAssignable (20.9.9.1.4)

Yes.

Whether extended alignment is supported (20.10.7.6)

Yes.

Whether values are rounded or truncated to the required precision when converting between time_t values and time_point objects (20.12.7.1)

Values are truncated.

The type of streamoff (21.2.3.1)

long long

The type of streampos (21.2.3.1)

Synonym for fpos<mbstate_t>

The return value of char_traits<char16_t>::eof (21.2.3.2)

int_type(-1)

The type of u16streampos (21.2.3.2)

Synonym for fpos<mbstate_t>

The return value of char_traits<char32_t>::eof (21.2.3.3)

int_type(-1)

The type of u32streampos (21.2.3.3)

Synonym for fpos<mbstate_t>

The type of wstreampos (21.2.3.4)

Synonym for fpos<mbstate_t>

Whether locale object is global or per-thread (22.3.1)

Locale object is global.

The effect on C locale of calling locale::global (22.3.1.5)

If the locale has a name, same as setlocale().

The value of ctype<char>::table_size (22.4.1.3)

SCHAR_MAX + 1

The additional formats accepted for time_get::do_get_date (22.4.5.1.2)

None

Whether time_get::do_get_year accepts two-digit year numbers (22.4.5.1.2)

Two-digit year numbers are accepted.

The formatted character sequence generated by time_put::do_put in the C locale (22.4.5.3.2)

Same as strftime()

The type of array::const_iterator (23.3.2.1)

const T*

The type of array::iterator (23.3.2.1)

T*

The default number of buckets in unordered_map when this is not specified with the constructor (23.5.4.2)

0

The default number of buckets in unordered_multimap when this is not specified with the constructor (23.5.5.2)

0

The default number of buckets in unordered_set when this is not specified with the constructor (23.5.6.2)

0

The default number of buckets in unordered_multiset when this is not specified with the constructor (23.5.7.2)

0

The underlying source of random numbers for random_shuffle (25.3.12)

It uses rand() as the source of randomness.

The effect of calling ios_base::sync_with_stdio after any input or output operation on standard streams (27.5.3.4)

The synchronization referred to is only that between the standard C facilities and the standard C++ objects. User-declared streams are unaffected.

The argument values used to construct the fail object of basic_ios::failure thrown by basic_ios flags functions (27.5.5.4)

const char&

Whether sequence pointers are copied by basic_stringbuf move constructor (27.8.2.1)

Sequence pointers are copied.

The effect of calling basic_streambuf::setbuf with non-zero arguments (27.8.2.4)

If no buffer has already been created, and both arguments are non-zero, then the first argument is used as a buffer.

Whether sequence pointers are copied by basic_filebuf move constructor (27.9.1.2)

Sequence pointers are copied.

The effect of calling basic_filebuf::setbuf with non-zero arguments (27.9.1.5)

The first argument is used as a buffer.

The effect of calling basic_filebuf::sync when a get area exists (27.9.1.5)

No effect.

The type of regex_constants::error_type (28.5.3)

Unscoped enumeration types.

The values of various ATOMIC_..._LOCK_FREE macros (29.4)

Not supported.

Whether get_pointer_safety returns pointer_safety::relaxed or pointer_safety::preferred if the implementation has relaxed pointer safety (29.4)

Relaxed pointer safety.

The presence and meaning of native_handle_type and native_handle (30.2.3)

Native handles are not supported.

The type of ios_base::streamoff (D.6)

long long int

The type of ios_base::streampos (D.6)

Typedef fpos<mbstate_t>