P2156R1 Allow Duplicate Attributes

Also fixes CWG1914.

Author: jensmaurer

source/declarations.tex

@@ -8493,8 +8493,8 @@
 
 \pnum
 The \grammarterm{attribute-token} \tcode{carries_dependency} specifies
-dependency propagation into and out of functions. It shall appear at most once
-in each \grammarterm{attribute-list} and no
+dependency propagation into and out of functions.
+No
 \grammarterm{attribute-argument-clause} shall be present. The attribute may be
 applied to the \grammarterm{declarator-id} of a
 \grammarterm{parameter-declaration} in a function declaration or lambda, in
@@ -8580,7 +8580,7 @@
 \tcode{deprecated} is appropriate for names and entities that are deemed obsolescent or
 unsafe.
 \end{note}
-It shall appear at most once in each \grammarterm{attribute-list}. An
+An
 \grammarterm{attribute-argument-clause} may be present and, if present, it shall have the form:
 \begin{ncbnf}
 \terminal{(} string-literal \terminal{)}
@@ -8630,9 +8630,7 @@
 may be applied to a null statement\iref{stmt.expr};
 \indextext{statement!fallthrough}
 such a statement is a fallthrough statement.
-The \grammarterm{attribute-token} \tcode{fallthrough}
-shall appear at most once in each \grammarterm{attribute-list} and
-no \grammarterm{attribute-argument-clause} shall be present.
+No \grammarterm{attribute-argument-clause} shall be present.
 A fallthrough statement may only appear within
 an enclosing \keyword{switch} statement\iref{stmt.switch}.
 The next statement that would be executed after a fallthrough statement
@@ -8692,10 +8690,7 @@
 The \grammarterm{attribute-token}s
 \tcode{likely} and \tcode{unlikely}
 may be applied to labels or statements.
-The \grammarterm{attribute-token}s
-\tcode{likely} and \tcode{unlikely}
-shall appear at most once in each \grammarterm{attribute-list}
-and no \grammarterm{attribute-argument-clause} shall be present.
+No \grammarterm{attribute-argument-clause} shall be present.
 The \grammarterm{attribute-token} \tcode{likely}
 shall not appear in an \grammarterm{attribute-specifier-seq}
 that contains the \grammarterm{attribute-token} \tcode{unlikely}.
@@ -8751,8 +8746,7 @@
 \pnum
 The \grammarterm{attribute-token} \tcode{maybe_unused}
 indicates that a name or entity is possibly intentionally unused.
-It shall appear at most once in each \grammarterm{attribute-list} and
-no \grammarterm{attribute-argument-clause} shall be present.
+No \grammarterm{attribute-argument-clause} shall be present.
 
 \pnum
 The attribute may be applied to the declaration of a class,
@@ -8798,7 +8792,6 @@
 The \grammarterm{attribute-token} \tcode{nodiscard}
 may be applied to the \grammarterm{declarator-id}
 in a function declaration or to the declaration of a class or enumeration.
-It shall appear at most once in each \grammarterm{attribute-list}.
 An \grammarterm{attribute-argument-clause} may be present
 and, if present, shall have the form:
 
@@ -8887,8 +8880,8 @@
 \indextext{attribute!noreturn}
 
 \pnum
-The \grammarterm{attribute-token} \tcode{noreturn} specifies that a function does not return. It
-shall appear at most once in each \grammarterm{attribute-list} and no
+The \grammarterm{attribute-token} \tcode{noreturn} specifies that a function does not return.
+No
 \grammarterm{attribute-argument-clause} shall be present. The attribute may be applied to the
 \grammarterm{declarator-id} in a function declaration. The first declaration of a function shall
 specify the \tcode{noreturn} attribute if any declaration of that function specifies the
@@ -8930,8 +8923,7 @@
 The \grammarterm{attribute-token} \tcode{no_unique_address}
 specifies that a non-static data member
 is a potentially-overlapping subobject\iref{intro.object}.
-It shall appear at most once in each \grammarterm{attribute-list}
-and no \grammarterm{attribute-argument-clause} shall be present.
+No \grammarterm{attribute-argument-clause} shall be present.
 The attribute may appertain to a non-static data member
 other than a bit-field.