Annex D (normative) Compatibility features [depr]

D.5 C standard library headers [depr.c.headers]

For compatibility with the C standard library, the C++ standard library provides the C headers shown in Table 141.
Table 141 — C headers
<assert.h>
<inttypes.h>
<signal.h>
<stdio.h>
<wchar.h>
<complex.h>
<iso646.h>
<stdalign.h>
<stdlib.h>
<wctype.h>
<ctype.h>
<limits.h>
<stdarg.h>
<string.h>
<errno.h>
<locale.h>
<stdbool.h>
<tgmath.h>
<fenv.h>
<math.h>
<stddef.h>
<time.h>
<float.h>
<setjmp.h>
<stdint.h>
<uchar.h>
The header <complex.h> behaves as if it simply includes the header <ccomplex>.
The header <tgmath.h> behaves as if it simply includes the header <ctgmath>.
Every other C header, each of which has a name of the form name.h, behaves as if each name placed in the standard library namespace by the corresponding cname header is placed within the global namespace scope, except for the functions described in [sf.cmath], the declaration of std​::​byte ([cstddef.syn]), and the functions and function templates described in [support.types.byteops].
It is unspecified whether these names are first declared or defined within namespace scope ([basic.scope.namespace]) of the namespace std and are then injected into the global namespace scope by explicit using-declarations.
[Example
:
The header <cstdlib> assuredly provides its declarations and definitions within the namespace std.
It may also provide these names within the global namespace.
The header <stdlib.h> assuredly provides the same declarations and definitions within the global namespace, much as in the C Standard.
It may also provide these names within the namespace std.
end example
]