16 Library introduction [library]

16.4 Library-wide requirements [requirements]

16.4.5 Constraints on programs [constraints]

16.4.5.3 Reserved names [reserved.names]

16.4.5.3.1 General [reserved.names.general]

The C++ standard library reserves the following kinds of names:
If a program declares or defines a name in a context where it is reserved, other than as explicitly allowed by [library], its behavior is undefined.

16.4.5.3.2 Zombie names [zombie.names]

In namespace std, the names shown in Table 38 are reserved for previous standardization:
Table 38: Zombie names in namespace std[tab:zombie.names.std]
auto_ptr
generate_header
pointer_to_binary_function
auto_ptr_ref
get_pointer_safety
pointer_to_unary_function
binary_function
get_temporary_buffer
ptr_fun
binary_negate
get_unexpected
random_shuffle
bind1st
gets
raw_storage_iterator
bind2nd
is_literal_type
result_of
binder1st
is_literal_type_v
result_of_t
binder2nd
istrstream
return_temporary_buffer
codecvt_mode
little_endian
set_unexpected
codecvt_utf16
mem_fun1_ref_t
strstream
codecvt_utf8
mem_fun1_t
strstreambuf
codecvt_utf8_utf16
mem_fun_ref_t
unary_function
const_mem_fun1_ref_t
mem_fun_ref
unary_negate
const_mem_fun1_t
mem_fun_t
uncaught_exception
const_mem_fun_ref_t
mem_fun
undeclare_no_pointers
const_mem_fun_t
not1
undeclare_reachable
consume_header
not2
unexpected_handler
declare_no_pointers
ostrstream
wbuffer_convert
declare_reachable
pointer_safety
wstring_convert
The names shown in Table 39 are reserved as members for previous standardization, and may not be used as a name for object-like macros in portable code:
Table 39: Zombie object-like macros [tab:zombie.names.objmacro]
argument_type
op
second_argument_type
first_argument_type
open_mode
seek_dir
io_state
preferred
strict
The names shown in Table 40 are reserved as member functions for previous standardization, and may not be used as a name for function-like macros in portable code:
Table 40: Zombie function-like macros [tab:zombie.names.fnmacro]
converted
freeze
from_bytes
pcount
stossc
to_bytes
The header names shown in Table 41 are reserved for previous standardization:
Table 41: Zombie headers [tab:zombie.names.header]
<ccomplex>
<codecvt>
<cstdbool>
<ctgmath>
<strstream>
<ciso646>
<cstdalign>

16.4.5.3.3 Macro names [macro.names]

A translation unit that includes a standard library header shall not #define or #undef names declared in any standard library header.
A translation unit shall not #define or #undef names lexically identical to keywords, to the identifiers listed in Table 4, or to the attribute-tokens described in [dcl.attr], except that the names likely and unlikely may be defined as function-like macros ([cpp.replace]).

16.4.5.3.4 External linkage [extern.names]

Each name declared as an object with external linkage in a header is reserved to the implementation to designate that library object with external linkage,156 both in namespace std and in the global namespace.
Each global function signature declared with external linkage in a header is reserved to the implementation to designate that function signature with external linkage.157
Each name from the C standard library declared with external linkage is reserved to the implementation for use as a name with extern "C" linkage, both in namespace std and in the global namespace.
Each function signature from the C standard library declared with external linkage is reserved to the implementation for use as a function signature with both extern "C" and extern "C++" linkage,158 or as a name of namespace scope in the global namespace.
156)156)
The list of such reserved names includes errno, declared or defined in <cerrno>.
157)157)
The list of such reserved function signatures with external linkage includes setjmp(jmp_buf), declared or defined in <csetjmp>, and va_end(va_list), declared or defined in <cstdarg>.
158)158)
The function signatures declared in <cuchar>, <cwchar>, and <cwctype> are always reserved, notwithstanding the restrictions imposed in subclause 4.5.1 of Amendment 1 to the C Standard for these headers.

16.4.5.3.5 Types [extern.types]

For each type T from the C standard library, the types ​::​T and std​::​T are reserved to the implementation and, when defined, ​::​T shall be identical to std​::​T.

16.4.5.3.6 User-defined literal suffixes [usrlit.suffix]

Literal suffix identifiers ([over.literal]) that do not start with an underscore are reserved for future standardization.
Literal suffix identifiers that contain a double underscore __ are reserved for use by C++ implementations.