This subclause summarizes the explicit changes in headers, definitions, declarations, or behavior between the C standard library in the C standard and the parts of the C++ standard library that were included from the C standard library.
For compatibility with the C standard library, the C++ standard library provides the C headers enumerated in [depr.c.headers], but their use is deprecated in C++.
There are no C++ headers for the C headers <stdatomic.h>, <stdnoreturn.h>, and <threads.h>, nor are the C headers themselves part of C++.
The C++headers <ccomplex> ([depr.ccomplex.syn]) and <ctgmath> ([depr.ctgmath.syn]), as well as their corresponding C headers <complex.h> and <tgmath.h>, do not contain any of the content from the C standard library and instead merely include other headers from the C++ standard library.
The headers <ciso646>, <cstdalign> ([depr.cstdalign.syn]), and <cstdbool> ([depr.cstdbool.syn]) are meaningless in C++. Use of the C++ headers <ccomplex>, <cstdalign>, <cstdbool>, and <ctgmath> is deprecated ([depr.c.headers]).
The token alignas is a keyword in this International Standard ([lex.key]). It does not appear as a macro name defined in <cstdalign> ([depr.cstdalign.syn]).
The tokens bool, true, and false are keywords in this International Standard. They do not appear as macro names defined in <cstdbool> ([depr.cstdbool.syn]).
Header <cstring>: The following functions have different declarations:
strchr
strpbrk
strrchr
strstr
memchr
Subclause [cstring.syn] describes the changes.
Header <cwchar>: The following functions have different declarations:
wcschr
wcspbrk
wcsrchr
wcsstr
wmemchr
Subclause [cwchar.syn] describes the changes.
Header <cstdlib>: The following functions have different behavior:
atexit
exit
abort
Subclause [support.start.term] describes the changes.
Header <csetjmp>: The following functions have different behavior:
longjmp
Subclause [csetjmp.syn] describes the changes.
The macro offsetof, defined in <cstddef>, accepts a restricted set of type arguments in this International Standard. Subclause [support.types.layout] describes the change.
The functions aligned_alloc, calloc, malloc, and realloc are restricted in this International Standard. Subclause [c.malloc] describes the changes.