On Mon, 15 Jan 2024, Jason Merrill wrote: > On 1/5/24 11:50, Patrick Palka wrote: > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK > > for trunk and perhaps 13? > > > > -- >8 -- > > > > invalid_tparm_referent_p was rejecting using the address of a class NTTP > > object as a template argument, but this should be fine. > > Hmm, I suppose so; https://eel.is/c++draft/temp#param-8 saying "No two > template parameter objects are template-argument-equivalent" suggests there > can be only one. And clang/msvc allow it. > > > PR c++/113242 > > > > gcc/cp/ChangeLog: > > > > * pt.cc (invalid_tparm_referent_p) <case ADDR_EXPR>: Suppress > > DECL_ARTIFICIAL rejection test for class NTTP objects. > > > > gcc/testsuite/ChangeLog: > > > > * g++.dg/cpp2a/nontype-class61.C: New test. > > --- > > gcc/cp/pt.cc | 3 ++- > > gcc/testsuite/g++.dg/cpp2a/nontype-class61.C | 27 ++++++++++++++++++++ > > 2 files changed, 29 insertions(+), 1 deletion(-) > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class61.C > > > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > > index 154ac76cb65..8c7d178328d 100644 > > --- a/gcc/cp/pt.cc > > +++ b/gcc/cp/pt.cc > > @@ -7219,7 +7219,8 @@ invalid_tparm_referent_p (tree type, tree expr, > > tsubst_flags_t complain) > > * a string literal (5.13.5), > > * the result of a typeid expression (8.2.8), or > > * a predefined __func__ variable (11.4.1). */ > > - else if (VAR_P (decl) && DECL_ARTIFICIAL (decl)) > > + else if (VAR_P (decl) && !DECL_NTTP_OBJECT_P (decl) > > + && DECL_ARTIFICIAL (decl)) > > If now some artificial variables are OK and others are not, perhaps we should > enumerate them either way and abort if it's one we haven't specifically > considered.
Sounds good, like so? Shall we backport this patch or the original patch to the 13 branch? -- >8 -- Subject: [PATCH] c++: address of class NTTP object as targ [PR113242] invalid_tparm_referent_p was rejecting using the address of a class NTTP object as a template argument, but this should be fine. This patch fixes this by refining the DECL_ARTIFICIAL rejection test to check specifically for the kinds of artificial variables we want to exclude. PR c++/113242 gcc/cp/ChangeLog: * pt.cc (invalid_tparm_referent_p) <case ADDR_EXPR>: Refine DECL_ARTIFICIAL rejection test. Assert that C++20 template parameter objects are the only artificial variables we accept. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/nontype-class61.C: New test. --- gcc/cp/pt.cc | 13 +++++++--- gcc/testsuite/g++.dg/cpp2a/nontype-class61.C | 27 ++++++++++++++++++++ 2 files changed, 37 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class61.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index b6117231de1..885c297450e 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -7212,12 +7212,14 @@ invalid_tparm_referent_p (tree type, tree expr, tsubst_flags_t complain) /* C++17: For a non-type template-parameter of reference or pointer type, the value of the constant expression shall not refer to (or for a pointer type, shall not be the address of): - * a subobject (4.5), + * a subobject (4.5), (relaxed in C++20) * a temporary object (15.2), - * a string literal (5.13.5), + * a string literal (5.13.5), (we diagnose this early in + convert_nontype_argument) * the result of a typeid expression (8.2.8), or * a predefined __func__ variable (11.4.1). */ - else if (VAR_P (decl) && DECL_ARTIFICIAL (decl)) + else if (VAR_P (decl) + && (DECL_TINFO_P (decl) || DECL_FNAME_P (decl))) { if (complain & tf_error) error ("the address of %qD is not a valid template argument", @@ -7242,6 +7244,11 @@ invalid_tparm_referent_p (tree type, tree expr, tsubst_flags_t complain) decl); return true; } + + /* The only artificial variables we do accept are C++20 + template parameter objects. */ + if (VAR_P (decl) && DECL_ARTIFICIAL (decl)) + gcc_checking_assert (DECL_NTTP_OBJECT_P (decl)); } break; diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class61.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class61.C new file mode 100644 index 00000000000..90805a05ecf --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class61.C @@ -0,0 +1,27 @@ +// PR c++/113242 +// { dg-do compile { target c++20 } } + +struct wrapper { + int n; +}; + +template<const wrapper& X> +void f1() { + static_assert(X.n == 42); +} + +template<const wrapper* X> +void f2() { + static_assert(X->n == 42); +} + +template<wrapper X> +void g() { + f1<X>(); + f2<&X>(); +} + +int main() { + constexpr wrapper X = {42}; + g<X>(); +} -- 2.43.0.367.g186b115d30