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c++: cv-qualified ref introduced by typedef [PR101783]

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The root cause of this bug is that it considers reference with
cv-qualifiers as an error by generating value for variable "bad_quals".
However, this is not correct for case of typedef. Here I quote spec
[dcl.ref]/1 :
"Cv-qualified references are ill-formed except when the cv-qualifiers
are introduced through the use of a typedef-name ([dcl.typedef],
[temp.param]) or decltype-specifier ([dcl.type.decltype]),
in which case the cv-qualifiers are ignored."

2021-09-30  qingzhe huang  <nickhuang99@hotmail.com>

gcc/cp/ChangeLog:
	PR c++/101783
	* tree.c (cp_build_qualified_type_real): Exclude typedef from
	error.

gcc/testsuite/ChangeLog:
	PR c++/101783
	* g++.dg/parse/pr101783.C: New test.
This commit is contained in:
qingzhe huang 2021-10-01 10:46:35 -04:00 • committed by Jason Merrill
parent 17374dab3e
commit 7c99923f8c
2 changed files with 13 additions and 1 deletions
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9
gcc/cp/tree.c
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@ -1403,11 +1403,18 @@ cp_build_qualified_type_real (tree type,
/* A reference or method type shall not be cv-qualified.
[dcl.ref], [dcl.fct]. This used to be an error, but as of DR 295
(in CD1) we always ignore extra cv-quals on functions. */
/* [dcl.ref/1] Cv-qualified references are ill-formed except when
the cv-qualifiers are introduced through the use of a typedef-name
([dcl.typedef], [temp.param]) or decltype-specifier
([dcl.type.decltype]),in which case the cv-qualifiers are
ignored. */
if (type_quals & (TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE)
&& (TYPE_REF_P (type)
|| FUNC_OR_METHOD_TYPE_P (type)))
{
if (TYPE_REF_P (type))
if (TYPE_REF_P (type)
&& (!typedef_variant_p (type) || FUNC_OR_METHOD_TYPE_P (type)))
bad_quals |= type_quals & (TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE);
type_quals &= ~(TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE);
}

5
gcc/testsuite/g++.dg/parse/pr101783.C Normal file
View file

@ -0,0 +1,5 @@
template<class T> struct A{
typedef T& Type;
};
template<class T> void f(const typename A<T>::Type){}
template <> void f<int>(const typename A<int>::Type){}