Merge 2021-06 CWG Motion 3

P2186R2 Removing Garbage Collection Support

Author: tkoeppe

source/basic.tex

@@ -4009,103 +4009,6 @@
 deallocation function shall deallocate the storage referenced by the
 pointer, ending the duration of the region of storage.
 
-\rSec4[basic.stc.dynamic.safety]{Safely-derived pointers}
-
-\pnum
-\indextext{pointer!safely-derived|(}%
-\indextext{pointer!to traceable object}%
-A \defn{traceable pointer object} is
-\begin{itemize}
-\item an object of an object pointer
-type\iref{basic.compound}, or
-\item an object of an integral type that is at least as large as \tcode{std::intptr_t},
-or
-\item a sequence of elements in an array of narrow character
-type\iref{basic.fundamental}, where the size and alignment of the sequence
-match those of some object pointer type.
-\end{itemize}
-
-\pnum
-A pointer value is a \defnadj{safely-derived}{pointer} to an object with dynamic storage duration
-only if the pointer value has an object pointer type
-and is one of the following:
-\begin{itemize}
-\item the value returned by a call to the \Cpp{} standard library implementation of
-\tcode{::\keyword{operator} \keyword{new}(std::\brk{}size_t)} or
-\tcode{::\keyword{operator} \keyword{new}(std::size_t, std::align_val_t)}%
-;%
-\begin{footnote}
-This subclause does not impose restrictions
-on indirection through pointers to memory not allocated by \tcode{::\keyword{operator} \keyword{new}}. This
-maintains the ability of many \Cpp{} implementations to use binary libraries and
-components written in other languages. In particular, this applies to C binaries,
-because indirection through pointers to memory allocated by \tcode{std::malloc} is not restricted.
-\end{footnote}
-
-\item the result of taking the address of an object (or one of its
-  subobjects) designated by an lvalue resulting from indirection
-  through a safely-derived pointer value;
-
-\item the result of well-defined pointer arithmetic\iref{expr.add} using a safely-derived pointer
-value;
-
-\item the result of a well-defined pointer
-conversion~(\ref{conv.ptr}, \ref{expr.type.conv}, \ref{expr.static.cast},
-\ref{expr.cast}) of a safely-derived pointer value;
-
-\item the result of a \keyword{reinterpret_cast} of a safely-derived pointer value;
-
-\item the result of a \keyword{reinterpret_cast} of an integer representation of a
-safely-derived pointer value;
-
-\item the value of an object whose value was copied from a traceable pointer object,
-where at the time of the copy the source object contained a copy of a safely-derived
-pointer value.
-\end{itemize}
-
-\pnum
-\indextext{integer representation}%
-\indextext{pointer!integer representation of safely-derived}%
-An integer value is an \defnx{integer representation of a safely-derived pointer}{safely-derived pointer!integer representation}
-only if its type is at least as large as \tcode{std::intptr_t} and it is one of the
-following:
-\begin{itemize}
-\item the result of a \keyword{reinterpret_cast} of a safely-derived pointer value;
-
-\item the result of a valid conversion of an integer representation of a safely-derived
-pointer value;
-
-\item the value of an object whose value was copied from a traceable pointer object,
-where at the time of the copy the source object contained an integer representation of a
-safely-derived pointer value;
-
-\item the result of an additive or bitwise operation, one of whose operands is an
-integer representation of a safely-derived pointer value \tcode{P}, if that result
-converted by \tcode{reinterpret_cast<void*>} would compare equal to a safely-derived
-pointer computable from \tcode{\keyword{reinterpret_cast}<\keyword{void}*>(P)}.
-\end{itemize}
-
-\pnum
-An implementation may have \defn{relaxed pointer safety}, in which case the
-validity of a pointer value does not depend on whether it is a safely-derived
-pointer value. Alternatively, an implementation may have \defn{strict pointer
-safety}, in which case a pointer value referring to an object with dynamic
-storage duration that is not a safely-derived pointer
-value is an invalid pointer value unless
-the referenced complete object has previously been declared
-reachable\iref{util.dynamic.safety}.
-\begin{note}
-The effect of using an invalid pointer value (including passing it to a
-deallocation function) is undefined, see~\ref{basic.stc}.
-This is true even if the unsafely-derived pointer value would compare equal to
-some safely-derived pointer value.
-\end{note}
-It is
-\impldef{whether an implementation has relaxed or strict pointer
-safety} whether an implementation has relaxed or strict pointer safety.%
-\indextext{pointer!safely-derived|)}%
-\indextext{storage duration!dynamic|)}
-
 \rSec3[basic.stc.inherit]{Duration of subobjects}
 
 \pnum

source/compatibility.tex

@@ -1556,16 +1556,6 @@
 
 \rSec2[diff.cpp03.utilities]{\ref{utilities}: general utilities library}
 
-\diffref{util.dynamic.safety}
-\change
-Minimal support for garbage-collected regions.
-\rationale
-Required by new feature.
-\effect
-Valid \CppIII{} code, compiled without traceable pointer support,
-that interacts with newer \Cpp{} code using regions declared reachable may
-have different runtime behavior.
-
 \diffref{refwrap,arithmetic.operations,comparisons,logical.operations,bitwise.operations}
 \change
 Standard function object types no longer derived from

source/expressions.tex

@@ -662,8 +662,7 @@
 the glvalue.
 
 \item Otherwise, if the object to which the glvalue refers contains an invalid
-pointer value~(\ref{basic.stc.dynamic.deallocation},
-\ref{basic.stc.dynamic.safety}), the behavior is
+pointer value~(\ref{basic.stc.dynamic.deallocation}), the behavior is
 \impldef{lvalue-to-rvalue conversion of an invalid pointer value}.
 
 \item Otherwise, the object indicated by the glvalue is read\iref{defns.access},
@@ -4010,10 +4009,6 @@
 \indextext{conversion!implementation-defined pointer integer}%
 mappings between pointers and integers are otherwise
 \impldef{conversions between pointers and integers}.
-\begin{note}
-Except as described in \ref{basic.stc.dynamic.safety}, the result of
-such a conversion will not be a safely-derived pointer value.
-\end{note}
 
 \pnum
 \indextext{cast!reinterpret!pointer-to-function}%

source/lib-intro.tex

@@ -2364,6 +2364,9 @@
 \item \indexlibraryzombie{const_mem_fun1_t} \tcode{const_mem_fun1_t},
 \item \indexlibraryzombie{const_mem_fun_ref_t} \tcode{const_mem_fun_ref_t},
 \item \indexlibraryzombie{const_mem_fun_t} \tcode{const_mem_fun_t},
+\item \indexlibraryzombie{declare_no_pointers} \tcode{declare_no_pointers},
+\item \indexlibraryzombie{declare_reachable} \tcode{declare_reachable},
+\item \indexlibraryzombie{get_pointer_safety} \tcode{get_pointer_safety},
 \item \indexlibraryzombie{get_temporary_buffer} \tcode{get_temporary_buffer},
 \item \indexlibraryzombie{get_unexpected} \tcode{get_unexpected},
 \item \indexlibraryzombie{gets} \tcode{gets},
@@ -2377,6 +2380,7 @@
 \item \indexlibraryzombie{mem_fun} \tcode{mem_fun},
 \item \indexlibraryzombie{not1} \tcode{not1},
 \item \indexlibraryzombie{not2} \tcode{not2},
+\item \indexlibraryzombie{pointer_safety} \tcode{pointer_safety},
 \item \indexlibraryzombie{pointer_to_binary_function} \tcode{pointer_to_binary_function},
 \item \indexlibraryzombie{pointer_to_unary_function} \tcode{pointer_to_unary_function},
 \item \indexlibraryzombie{ptr_fun} \tcode{ptr_fun},
@@ -2389,22 +2393,25 @@
 \item \indexlibraryzombie{unary_function} \tcode{unary_function},
 \item \indexlibraryzombie{unary_negate} \tcode{unary_negate},
 \item \indexlibraryzombie{uncaught_exception} \tcode{uncaught_exception},
+\item \indexlibraryzombie{undeclare_no_pointers} \tcode{undeclare_no_pointers},
+\item \indexlibraryzombie{undeclare_reachable} \tcode{undeclare_reachable},
 \item \indexlibraryzombie{unexpected} \tcode{unexpected},
 and
 \item \indexlibraryzombie{unexpected_handler} \tcode{unexpected_handler}.
 \end{itemize}
 
 \pnum
-The following names are reserved as member types for previous standardization,
+The following names are reserved as members for previous standardization,
 and may not be used as a name for object-like macros in portable code:
 \begin{itemize}
 \item \indexlibraryzombie{argument_type} \tcode{argument_type},
 \item \indexlibraryzombie{first_argument_type} \tcode{first_argument_type},
 \item \indexlibraryzombie{io_state} \tcode{io_state},
 \item \indexlibraryzombie{open_mode} \tcode{open_mode},
+\item \indexlibraryzombie{preferred} \tcode{preferred},
 \item \indexlibraryzombie{second_argument_type} \tcode{second_argument_type},
-and
-\item \indexlibraryzombie{seek_dir} \tcode{seek_dir}.
+\item \indexlibraryzombie{seek_dir} \tcode{seek_dir}, and.
+\item \indexlibraryzombie{strict} \tcode{strict}.
 \end{itemize}
 
 \pnum
@@ -3135,15 +3142,6 @@
 for a non-virtual function
 by adding a non-throwing exception specification.
 
-\rSec3[res.on.pointer.storage]{Restrictions on storage of pointers}
-
-\pnum
-\indextext{traceable pointer object}%
-\indextext{pointer!to traceable object}%
-Objects constructed by the standard library that may hold a user-supplied pointer value
-or an integer of type \tcode{std::intptr_t} shall store such values in a traceable
-pointer location\iref{basic.stc.dynamic.safety}.
-
 \rSec3[value.error.codes]{Value of error codes}
 
 \pnum

source/preprocessor.tex

@@ -1850,12 +1850,6 @@
 the characters that are defined by ISO/IEC 10646, along with
 all amendments and technical corrigenda as of the specified year and month.
 
-\item
-\indextext{__stdcpp_strict_pointer_safety__@\mname{STDCPP_STRICT_POINTER_SAFETY}}%
-\mname{STDCPP_STRICT_POINTER_SAFETY}\\
-Defined, and has the value integer literal 1, if and only if the implementation
-has strict pointer safety\iref{basic.stc.dynamic.safety}.
-
 \item
 \indextext{__stdcpp_threads__@\mname{STDCPP_THREADS}}%
 \mname{STDCPP_THREADS}\\

source/support.tex

@@ -2381,10 +2381,6 @@
 which has not been invalidated by an intervening call to
 \tcode{operator delete}.
 
-\pnum
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 If the \tcode{alignment} parameter is not present,
 \tcode{ptr} was returned by an allocation function
@@ -2481,10 +2477,6 @@
 which has not been invalidated by an intervening call to
 \tcode{operator delete}.
 
-\pnum
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 If the \tcode{alignment} parameter is not present,
 \tcode{ptr} was returned by an allocation function
@@ -2632,10 +2624,6 @@
 which has not been invalidated by an intervening call to
 \tcode{operator delete[]}.
 
-\pnum
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 If the \tcode{alignment} parameter is not present,
 \tcode{ptr} was returned by an allocation function
@@ -2712,10 +2700,6 @@
 which has not been invalidated by an intervening call to
 \tcode{operator delete[]}.
 
-\pnum
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 If the \tcode{alignment} parameter is not present,
 \tcode{ptr} was returned by an allocation function
@@ -2798,11 +2782,6 @@
 \end{itemdecl}
 
 \begin{itemdescr}
-\pnum
-\expects
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 \effects
 Intentionally performs no action.
@@ -2821,11 +2800,6 @@
 \end{itemdecl}
 
 \begin{itemdescr}
-\pnum
-\expects
-If an implementation has strict pointer safety\iref{basic.stc.dynamic.safety}
-then \tcode{ptr} is a safely-derived pointer.
-
 \pnum
 \effects
 Intentionally performs no action.