[diff.mods.to.definitions]

# Annex C (informative) Compatibility [[diff]](./#diff)

## C.8 C standard library [[diff.library]](diff.library#diff.mods.to.definitions)

### C.8.3 Modifications to definitions [diff.mods.to.definitions]

#### [C.8.3.1](#diff.char16) Types char8_t, char16_t, and char32_t [[diff.char16]](diff.char16)

[1](#diff.char16-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/compatibility.tex#L3711)

The types char8_t, char16_t, and char32_t are distinct types rather than typedefs to existing integral types[.](#diff.char16-1.sentence-1)

The tokens char8_t, char16_t, and char32_t are keywords in C++ ([[lex.key]](lex.key "5.12 Keywords"))[.](#diff.char16-1.sentence-2)

They do not appear as macro or type names defined in[<cuchar>](cuchar.syn#header:%3ccuchar%3e "28.7.4 Header <cuchar> synopsis [cuchar.syn]")[.](#diff.char16-1.sentence-3)

#### [C.8.3.2](#diff.wchar.t) Type wchar_t [[diff.wchar.t]](diff.wchar.t)

[1](#diff.wchar.t-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/compatibility.tex#L3721)

The type wchar_t is a distinct type rather than a typedef to an
existing integral type[.](#diff.wchar.t-1.sentence-1)

The token wchar_t is a keyword in C++ ([[lex.key]](lex.key "5.12 Keywords"))[.](#diff.wchar.t-1.sentence-2)

It does not appear as a macro or type name defined in any of[<cstddef>](cstddef.syn#header:%3ccstddef%3e "17.2.1 Header <cstddef> synopsis [cstddef.syn]"),[<cstdlib>](cstdlib.syn#header:%3ccstdlib%3e "17.2.2 Header <cstdlib> synopsis [cstdlib.syn]"),
or [<cwchar>](cwchar.syn#header:%3ccwchar%3e "28.7.3 Header <cwchar> synopsis [cwchar.syn]")[.](#diff.wchar.t-1.sentence-3)

#### [C.8.3.3](#diff.header.iso646.h) Header <iso646.h> [[diff.header.iso646.h]](diff.header.iso646.h)

[1](#diff.header.iso646.h-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/compatibility.tex#L3733)

The tokensand,and_eq,bitand,bitor,compl,not,not_eq,or,or_eq,xor,
andxor_eq are keywords in C++ ([[lex.key]](lex.key "5.12 Keywords")),
and are not introduced as macros
by [<iso646.h>](iso646.h.syn#header:%3ciso646.h%3e "17.15.3 Header <iso646.h> synopsis [iso646.h.syn]")[.](#diff.header.iso646.h-1.sentence-1)

#### [C.8.3.4](#diff.null) Macro NULL [[diff.null]](diff.null)

[1](#diff.null-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/compatibility.tex#L3753)

The macroNULL,
defined in any of[<clocale>](clocale.syn#header:%3cclocale%3e "28.3.5.1 Header <clocale> synopsis [clocale.syn]"),[<cstddef>](cstddef.syn#header:%3ccstddef%3e "17.2.1 Header <cstddef> synopsis [cstddef.syn]"),[<cstdio>](cstdio.syn#header:%3ccstdio%3e "31.13.1 Header <cstdio> synopsis [cstdio.syn]"),[<cstdlib>](cstdlib.syn#header:%3ccstdlib%3e "17.2.2 Header <cstdlib> synopsis [cstdlib.syn]"),[<cstring>](cstring.syn#header:%3ccstring%3e "27.5.1 Header <cstring> synopsis [cstring.syn]"),[<ctime>](ctime.syn#header:%3cctime%3e "30.15 Header <ctime> synopsis [ctime.syn]"),
or [<cwchar>](cwchar.syn#header:%3ccwchar%3e "28.7.3 Header <cwchar> synopsis [cwchar.syn]"),
is an implementation-defined null pointer constant in
C++ ([[support.types]](support.types "17.2 Common definitions"))[.](#diff.null-1.sentence-1)