P2465R3 Standard Library Modules std and std.compat

source/basic.tex

@@ -3876,12 +3876,14 @@
 or any other names that the library uses to
 declare these names. Thus, a \grammarterm{new-expression},
 \grammarterm{delete-expression}, or function call that refers to one of
-these functions without importing or including the header \libheaderref{new} is
-well-formed. However, referring to \tcode{std}
+these functions without importing or including the header \libheaderref{new}
+or importing a \Cpp{} library module\iref{std.modules}
+is well-formed. However, referring to \tcode{std}
 or \tcode{std::size_t}
 or \tcode{std::align_val_t}
-is ill-formed unless the name has been declared
-by importing or including the appropriate header.
+is ill-formed unless
+a standard library declaration\iref{cstddef.syn,new.syn,std.modules}
+of that name precedes\iref{basic.lookup.general} the use of that name.
 \end{note}
 Allocation and/or
 deallocation functions may also be declared and defined for any

source/declarations.tex

@@ -1901,6 +1901,10 @@
 the deduced type
 $\mathtt{T}'$ replacing \tcode{T}
 is determined using the rules for template argument deduction.
+If the initialization is copy-list-initialization,
+a declaration of \tcode{std::initializer_list}
+shall precede\iref{basic.lookup.general}
+the \grammarterm{placeholder-type-specifier}.
 Obtain \tcode{P} from
 \tcode{T} by replacing the occurrences of
 \opt{\grammarterm{type-constraint}} \keyword{auto} either with
@@ -5653,10 +5657,12 @@
 corresponding parameter to be a non-deduced context\iref{temp.deduct.call}.
 \end{note}
 The template
-\tcode{std::initializer_list} is not predefined; if the header
-\tcode{<initializer_list>} is not imported or included prior to a use of
-\tcode{std::initializer_list} --- even an implicit use in which the type is not
-named\iref{dcl.spec.auto} --- the program is ill-formed.
+\tcode{std::initializer_list} is not predefined;
+if a standard library declaration\iref{initializer.list.syn,std.modules}
+of \tcode{std::initializer_list} is not reachable from\iref{module.reach}
+a use of \tcode{std::initializer_list} ---
+even an implicit use in which the type is not named\iref{dcl.spec.auto} ---
+the program is ill-formed.
 
 \pnum
 List-initialization of an object or reference of type \tcode{T} is defined as follows:

source/expressions.tex

@@ -3939,9 +3939,10 @@
 \end{example}
 
 \pnum
-If the header \libheaderref{typeinfo}
-is not imported or included prior
-to a use of \keyword{typeid}, the program is ill-formed.
+The type \tcode{std::type_info}\iref{type.info} is not predefined;
+if a standard library declaration\iref{typeinfo.syn,std.modules} of
+\tcode{std::type_info} does not precede\iref{basic.lookup.general}
+a \tcode{typeid} expression, the program is ill-formed.
 
 \pnum
 \begin{note}
@@ -6429,8 +6430,9 @@
 \tcode{std::weak_ordering}, and
 \tcode{std::partial_ordering})
 are not predefined;
-if the header \libheaderref{compare}
-is not imported or included prior to a use of such a class type --
+if a standard library declaration\iref{compare.syn,std.modules}
+of such a class type does not precede\iref{basic.lookup.general}
+a use of that type --
 even an implicit use in which the type is not named
 (e.g., via the \keyword{auto} specifier\iref{dcl.spec.auto}
 in a defaulted three-way comparison\iref{class.spaceship}

source/lib-intro.tex

@@ -1363,6 +1363,62 @@
 \tcode{wscanf_s} \\
 \end{multicolfloattable}
 
+\rSec3[std.modules]{Modules}
+
+\pnum
+The \Cpp{} standard library provides
+the following \defn{\Cpp{} library modules}.
+
+\pnum
+The named module \tcode{std} exports declarations in namespace \tcode{std}
+that are provided by the importable \Cpp{} library headers
+(\tref{headers.cpp} or the subset provided by a freestanding implementation)
+and the \Cpp{} headers for C library facilities~(\tref{headers.cpp.c}).
+It additionally exports declarations in the global namespace
+for the storage allocation and deallocation functions
+that are provided by \libheaderref{new}.
+
+\pnum
+The named module \tcode{std.compat} exports the same declarations as
+the named module \tcode{std}, and
+additionally exports declarations in the global namespace
+corresponding to the declarations in namespace \tcode{std}
+that are provided by
+the \Cpp{} headers for C library facilities~(\tref{headers.cpp.c}).
+
+\pnum
+It is unspecified to which module a declaration in the standard library
+is attached.
+\begin{note}
+Implementations are required to ensure that mixing
+\tcode{\#include} and \tcode{import} does not result in
+conflicting attachments\iref{basic.link}.
+\end{note}
+\recommended
+Implementations should ensure such attachments do not preclude
+further evolution or decomposition of the standard library modules.
+
+\pnum
+A declaration in the standard library denotes the same entity regardless of
+whether it was made reachable through
+including a header,
+importing a header unit, or
+importing a \Cpp{} library module.
+
+\pnum
+\recommended
+Implementations should avoid exporting any other declarations
+from the \Cpp{} library modules.
+
+\begin{note}
+Like all named modules, the \Cpp{} library modules
+do not make macros visible\iref{module.import}, such as
+\tcode{assert}\iref{cassert.syn},
+\tcode{errno}\iref{cerrno.syn},
+\tcode{offsetof}\iref{cstddef.syn}, and
+\tcode{va_arg}\iref{cstdarg.syn}.
+\end{note}
+
 \rSec3[compliance]{Freestanding implementations}
 \indextext{implementation!freestanding|(}%
 

source/support.tex

@@ -664,6 +664,7 @@
 #define @\defnlibxname{cpp_lib_math_special_functions}@            201603L // also in \libheader{cmath}
 #define @\defnlibxname{cpp_lib_mdspan}@                            202207L // also in \libheader{mdspan}
 #define @\defnlibxname{cpp_lib_memory_resource}@                   201603L // also in \libheader{memory_resource}
+#define @\defnlibxname{cpp_lib_modules}@                           202207L
 #define @\defnlibxname{cpp_lib_move_only_function}@                202110L // also in \libheader{functional}
 #define @\defnlibxname{cpp_lib_node_extract}@                      201606L
   // also in \libheader{map}, \libheader{set}, \libheader{unordered_map}, \libheader{unordered_set}