[depr.c.headers] Undo P0619R4's removal of synopses for <ccomplex>,

<cstdalign>, <cstdbool>, and <ctgmath>.

Instead, repurpose these to be synopses for <complex.h>, <stdalign.h>,
<stdbool.h>, and <tgmath.h>, and move them into [depr.c.headers].
Also introduce a synopsis for <iso646.h>.

This avoids three of these five headers being specified as equivalent to
a non-existent <cfoo> header, and the other two missing a synopsis.

Author: zygoloid

source/compatibility.tex

@@ -2134,11 +2134,11 @@
 in~\ref{depr.c.headers}, but their use is deprecated in \Cpp{}.
 
 \pnum
-There are no \Cpp{} headers for the C headers
+There are no \Cpp{} headers for the C standard library's headers
 \tcode{<stdatomic.h>}\indextext{\idxhdr{stdatomic.h}!absence thereof},
 \tcode{<stdnoreturn.h>}\indextext{\idxhdr{stdnoreturn.h}!absence thereof},
 and \tcode{<threads.h>}\indextext{\idxhdr{threads.h}!absence thereof},
-nor are the C headers themselves part of \Cpp{}.
+nor are these headers from the C standard library headers themselves part of \Cpp{}.
 
 \pnum
 The C headers \tcode{<complex.h>}\indexhdr{complex.h} and
@@ -2196,21 +2196,27 @@
 and
 \tcode{xor_eq}
 are keywords in this International
-Standard\iref{lex.key}.
+Standard\iref{lex.key},
+and are not introduced as macros
+by \tcode{<iso646.h>}\iref{depr.iso646.h.syn}.
 
 \rSec3[diff.header.stdalign.h]{Header \tcode{<stdalign.h>}}
 \indexhdr{stdalign.h}%
 
 \pnum
 The token \tcode{alignas} is a keyword in this International
-Standard\iref{lex.key}.
+Standard\iref{lex.key},
+and is not introduced as a macro
+by \tcode{<stdalign.h>}\iref{depr.stdalign.h.syn}.
 
 \rSec3[diff.header.stdbool.h]{Header \tcode{<stdbool.h>}}
 \indexhdr{stdbool.h}%
 
 \pnum
 The tokens \tcode{bool}, \tcode{true}, and \tcode{false}
-are keywords in this International Standard\iref{lex.key}.
+are keywords in this International Standard\iref{lex.key},
+and are not introduced as macros
+by \tcode{<stdbool.h>}\iref{depr.stdbool.h.syn}.
 
 \rSec3[diff.null]{Macro \tcode{NULL}}
 

source/future.tex

@@ -110,57 +110,155 @@
 C standard library, the \Cpp{} standard library provides
 the \defnx{C headers}{headers!C library} shown in \tref{future.c.headers}.
 
-\begin{floattable}{C headers}{tab:future.c.headers}
+\begin{multicolfloattable}{C headers}{tab:future.c.headers}
 {lllll}
-\topline
+\tcode{<assert.h>} \\
+\tcode{<complex.h>} \\
+\tcode{<ctype.h>} \\
+\tcode{<errno.h>} \\
+\tcode{<fenv.h>} \\
+\tcode{<float.h>} \\
+\columnbreak
+\tcode{<inttypes.h>} \\
+\tcode{<iso646.h>} \\
+\tcode{<limits.h>} \\
+\tcode{<locale.h>} \\
+\tcode{<math.h>} \\
+\tcode{<setjmp.h>} \\
+\columnbreak
+\tcode{<signal.h>} \\
+\tcode{<stdalign.h>} \\
+\tcode{<stdarg.h>} \\
+\tcode{<stdbool.h>} \\
+\tcode{<stddef.h>} \\
+\tcode{<stdint.h>} \\
+\columnbreak
+\tcode{<stdio.h>} \\
+\tcode{<stdlib.h>} \\
+\tcode{<string.h>} \\
+\tcode{<tgmath.h>} \\
+\tcode{<time.h>} \\
+\tcode{<uchar.h>} \\
+\columnbreak
+\tcode{<wchar.h>} \\
+\tcode{<wctype.h>} \\
+\end{multicolfloattable}
+
+\rSec2[depr.complex.h.syn]{Header \tcode{<complex.h>} synopsis}
+
+\indexhdr{complex.h}%
+\begin{codeblock}
+#include <complex>
+\end{codeblock}
+
+\pnum
+The header \tcode{<complex.h>}
+behaves as if it simply includes the header
+\tcode{<complex>}\iref{complex.syn}.
+
+\pnum
+\begin{note}
+Names introduced by \tcode{<complex>} in namespace \tcode{std}
+are not placed into the global namespace scope by \tcode{<complex.h>}.
+\end{note}
+
+\rSec2[depr.iso646.h.syn]{Header \tcode{<iso646.h>} synopsis}
+
+\indexhdr{iso646.h}%
+\pnum
+The \Cpp{} header \tcode{<iso646.h>} is empty.
+\begin{note}
+\tcode{and},
+\tcode{and_eq},
+\tcode{bitand},
+\tcode{bitor},
+\tcode{compl},
+\tcode{not_eq},
+\tcode{not},
+\tcode{or},
+\tcode{or_eq},
+\tcode{xor}, and
+\tcode{xor_eq}
+are keywords in this International Standard\iref{lex.key}.
+\end{note}
+
+\rSec2[depr.stdalign.h.syn]{Header \tcode{<stdalign.h>} synopsis}
+
+\indexlibrary{\idxcode{__alignas_is_defined}}%
+\indexhdr{stdalign.h}%
+\begin{codeblock}
+#define @\xname{alignas_is_defined}@ 1
+\end{codeblock}
+
+\pnum
+\indexhdr{stdalign.h}%
+The contents of the \Cpp{} header \tcode{<stdalign.h>} are the same as the C
+standard library header \tcode{<stdalign.h>}, with the following changes:
+The header \tcode{<stdalign.h>} does not
+define a macro named \tcode{alignas}.
+
+\xrefc{7.15}
 
-\tcode{<assert.h>}			&
-\tcode{<inttypes.h>}		&
-\tcode{<signal.h>}			&
-\tcode{<stdio.h>}			  &
-\tcode{<wchar.h>}			  \\
+\rSec2[depr.stdbool.h.syn]{Header \tcode{<stdbool.h>} synopsis}
 
-\tcode{<complex.h>}			&
-\tcode{<iso646.h>}			&
-\tcode{<stdalign.h>}    &
-\tcode{<stdlib.h>}			&
-\tcode{<wctype.h>}			\\
+\indexhdr{stdbool.h}%
+\indexlibrary{\idxcode{__bool_true_false_are_defined}}%
+\begin{codeblock}
+#define @\xname{bool_true_false_are_defined}@ 1
+\end{codeblock}
+
+\pnum
+\indexhdr{stdbool.h}%
+The contents of the \Cpp{} header \tcode{<stdbool.h>} are the same as the C
+standard library header \tcode{<stdbool.h>}, with the following changes:
+The header \tcode{<stdbool.h>} does not
+define macros named \tcode{bool}, \tcode{true}, or \tcode{false}.
 
-\tcode{<ctype.h>}			  &
-\tcode{<limits.h>}			&
-\tcode{<stdarg.h>}			&
-\tcode{<string.h>}			& \\
+\xrefc{7.18}
 
-\tcode{<errno.h>}			  &
-\tcode{<locale.h>}			&
-\tcode{<stdbool.h>}			&
-\tcode{<tgmath.h>}			& \\
+\rSec2[depr.tgmath.h.syn]{Header \tcode{<tgmath.h>} synopsis}
 
-\tcode{<fenv.h>}			  &
-\tcode{<math.h>}			  &
-\tcode{<stddef.h>}			&
-\tcode{<time.h>}				& \\
+\indexhdr{tgmath.h}%
+\begin{codeblock}
+#include <cmath>
+#include <complex>
+\end{codeblock}
 
-\tcode{<float.h>}			  &
-\tcode{<setjmp.h>}			&
-\tcode{<stdint.h>}			&
-\tcode{<uchar.h>}			  & \\
+\pnum
+The header \tcode{<tgmath.h>}
+behaves as if it simply includes the headers
+\tcode{<cmath>}\iref{cmath.syn} and
+\tcode{<complex>}\iref{complex.syn}.
 
-\end{floattable}
+\pnum
+\begin{note} The overloads provided in C by type-generic macros are already
+provided in \tcode{<complex>} and \tcode{<cmath>} by ``sufficient'' additional
+overloads.\end{note}
 
 \pnum
-The header \tcode{<complex.h>} behaves as if it simply includes the header \tcode{<complex>}\iref{complex.syn}.
-The header \tcode{<tgmath.h>} behaves as if it simply includes the headers \tcode{<complex>}\iref{complex.syn}
-and \tcode{<cmath>}\iref{cmath.syn}.
+\begin{note}
+Names introduced by \tcode{<cmath>} or \tcode{<complex>}
+in namespace \tcode{std}
+are not placed into the global namespace scope by \tcode{<tgmath.h>}.
+\end{note}
+
+\rSec2[depr.c.headers.other]{Other C headers}
 
 \pnum
-Every other C header, each of
+Every C header
+other than
+\tcode{<complex.h>},
+\tcode{<iso646.h>},
+\tcode{<stdalign.h>},
+\tcode{<stdbool.h>}, and
+\tcode{<tgmath.h>},
+each of
 which has a name of the form
 \indextext{header!C}%
-\tcode{name.h},
+\tcode{<\placeholder{name}.h>},
 behaves as if each name placed in the standard library namespace by
 the corresponding
-\tcode{c\textit{name}}
+\tcode{<c\placeholder{name}>}
 header is placed within
 the global namespace scope,
 except for the functions described in \ref{sf.cmath},
@@ -188,7 +286,6 @@
 much as in the C Standard. It may also provide these names within
 the namespace \tcode{std}.
 \end{example}
-
 \rSec1[depr.relops]{Relational operators}
 
 \pnum

source/xrefdelta.tex

@@ -120,10 +120,6 @@
 % Deprecated features were removed.
 \removedxref{depr.except.spec}
 \removedxref{depr.cpp.headers}
-\removedxref{depr.ccomplex.syn}
-\removedxref{depr.cstdalign.syn}
-\removedxref{depr.cstdbool.syn}
-\removedxref{depr.ctgmath.syn}
 \removedxref{depr.uncaught}
 \removedxref{depr.func.adaptor.binding}
 \removedxref{depr.weak.result_type}
@@ -134,6 +130,12 @@
 \removedxref{depr.temporary.buffer}
 \removedxref{depr.util.smartptr.shared.obs}
 
+% Deprecated <cfoo> headers were removed for some <foo.h> headers
+\movedxref{depr.ccomplex.syn}{depr.complex.h.syn}
+\movedxref{depr.cstdalign.syn}{depr.stdalign.h.syn}
+\movedxref{depr.cstdbool.syn}{depr.stdbool.h.syn}
+\movedxref{depr.ctgmath.syn}{depr.tgmath.h.syn}
+
 % Deprecated features.
 %\deprxref{old.label}  (if moved to depr.old.label, otherwise use \movedxref)