[2025-02 CWG Motion 5] P2900R14 - Contracts for C++

source/classes.tex

@@ -475,8 +475,8 @@
 
 \begin{bnf}
 \nontermdef{member-declarator}\br
-    declarator \opt{virt-specifier-seq} \opt{pure-specifier}\br
-    declarator requires-clause\br
+    declarator \opt{virt-specifier-seq} \opt{function-contract-specifier-seq} \opt{pure-specifier}\br
+    declarator requires-clause \opt{function-contract-specifier-seq}\br
     declarator brace-or-equal-initializer\br
     \opt{identifier} \opt{attribute-specifier-seq} \terminal{:} constant-expression \opt{brace-or-equal-initializer}
 \end{bnf}
@@ -527,6 +527,12 @@
 the program is ill-formed; see~\ref{temp.spec.general}.
 \end{note}
 
+\pnum
+The optional \grammarterm{function-contract-specifier-seq}\iref{dcl.contract.func})
+in a \grammarterm{member-declarator}
+shall be present only if
+the \grammarterm{declarator} declares a function.
+
 \pnum
 \indextext{definition!class}%
 The \grammarterm{member-specification} in a class definition declares the
@@ -618,7 +624,8 @@
 \item function body\iref{dcl.fct.def.general},
 \item default argument\iref{dcl.fct.default},
 \item default template argument\iref{temp.param},
-\item \grammarterm{noexcept-specifier}\iref{except.spec}, or
+\item \grammarterm{noexcept-specifier}\iref{except.spec},
+\item \grammarterm{function-contract-specifier}\iref{dcl.contract.func}, or
 \item default member initializer
 \end{itemize}
 within the \grammarterm{member-specification} of the class or class template.
@@ -4289,17 +4296,17 @@
 \begin{codeblock}
 class A {
   typedef int I;    // private member
-  I f();
-  friend I g(I);
+  I f() pre(A::x > 0);
+  friend I g(I) post(A::x <= 0);
   static I x;
   template<int> struct Q;
   template<int> friend struct R;
 protected:
     struct B { };
 };
 
-A::I A::f() { return 0; }
-A::I g(A::I p = A::x);
+A::I A::f() pre(A::x > 0) { return 0; }
+A::I g(A::I p = A::x) post(A::x <= 0);
 A::I g(A::I p) { return 0; }
 A::I A::x = 0;
 template<A::I> struct A::Q { };
@@ -5715,18 +5722,27 @@
 \pnum
 \indextext{initialization!member function call during}%
 Member functions (including virtual member functions, \ref{class.virtual}) can be
-called for an object under construction.
-Similarly, an object under construction can be the operand of the
+called for an object under construction or destruction.
+Similarly, an object under construction or destruction can be the operand of the
 \tcode{typeid}
 operator\iref{expr.typeid} or of a
 \keyword{dynamic_cast}\iref{expr.dynamic.cast}.
-However, if these operations are performed in a
-\grammarterm{ctor-initializer}
+However, if these operations are performed
+during evaluation of
+\begin{itemize}
+\item
+a \grammarterm{ctor-initializer}
 (or in a function called directly or indirectly from a
 \grammarterm{ctor-initializer})
 before all the
 \grammarterm{mem-initializer}{s}
-for base classes have completed, the program has undefined behavior.
+for base classes have completed,
+\item
+a precondition assertion of a constructor, or
+\item
+a postcondition assertion of a destructor\iref{dcl.contract.func},
+\end{itemize}
+the program has undefined behavior.
 \begin{example}
 \begin{codeblock}
 class A {
@@ -6049,6 +6065,9 @@
 or from a destructor,
 including during the construction or destruction of the class's non-static data
 members,
+or during the evaluation of
+a postcondition assertion of a constructor or
+a precondition assertion of a destructor\iref{dcl.contract.func},
 and the object to which the call applies is the object (call it \tcode{x}) under construction or
 destruction,
 the function called is the

source/compatibility.tex

@@ -11,6 +11,23 @@
 ISO \CppXXIII{},
 by the chapters of this document.
 
+\rSec2[diff.cpp23.lex]{\ref{lex}: Lexical conventions}
+
+\diffref{lex.key}
+\change
+New keywords.
+\rationale
+Required for new features.
+\begin{itemize}
+\item
+The \keyword{contract_assert} keyword
+is added to introduce a contract assertion
+through an \grammarterm{assertion-statement}\iref{stmt.contract.assert}.
+\end{itemize}
+\effect
+Valid \CppXXIII{} code using \keyword{contract_assert} as an identifier
+is not valid in this revision of \Cpp{}.
+
 \rSec2[diff.cpp23.expr]{\ref{expr}: expressions}
 
 \diffref{expr.arith.conv}
@@ -182,6 +199,7 @@
 New functionality.
 \effect
 The following \Cpp{} headers are new:
+\libheaderrefx{contracts}{support.contract},
 \libheaderref{debugging},
 \libheaderrefx{hazard_pointer}{hazard.pointer.syn},
 \libheaderrefx{inplace_vector}{inplace.vector.syn},