| Message ID | 20210218083001.GY4020736@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Fix -std=c++20 ICE on virtual method call [PR99132] | expand |
On 2/18/21 3:30 AM, Jakub Jelinek wrote: > Hi! > > On the following testcase we ICE in C++20 mode during cp_get_callee_fndecl > -> constexpr evaluation. > It is only in C++20 mode on this testcase because virtual methods can't > be constexpr in C++17 and earlier and so potential_constant_expression_1 > rejects it earlier. > And the ICE is caused by genericization changing the h PARM_DECL from having > B<C *> type to B<C *> & DECL_BY_REFERENCE and the constexpr evaluation > not being able to deal with that. > I think this just shows that we shouldn't do the constexpr evaluation during > genericization and later, and other spots e.g. during gimplification > also don't call cp_get_callee_fndecl but cp_get_callee_fndecl_nofold. Agreed, we've run into this kind of thing before. > After all, cp_fold has already been run and it did the folding if there > was any opportunity to do so. And furthermore, what that cp_genericize_r > spot does is check for any left-over immediate function calls (which can be > ATM just std::source_location::current() call) and immediate functions > outside of immediate functions can't have addresses leaked into the IL, > so it will be always a direct call anyway. And immediate functions > themselves don't make it into genericization/gimplification. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? ok, thanks > > 2021-02-18 Jakub Jelinek <jakub@redhat.com> > > PR c++/99132 > * cp-gimplify.c (cp_genericize_r) <case CALL_EXPR>: Use > cp_get_callee_fndecl_nofold instead of cp_get_callee_fndecl to check > for immediate function calls. > > * g++.dg/cpp2a/constexpr-virtual18.C: New test. > > --- gcc/cp/cp-gimplify.c.jj 2021-02-17 16:14:42.621294819 +0100 > +++ gcc/cp/cp-gimplify.c 2021-02-17 16:48:30.343291226 +0100 > @@ -1386,7 +1386,7 @@ cp_genericize_r (tree *stmt_p, int *walk > break; > } > > - if (tree fndecl = cp_get_callee_fndecl (stmt)) > + if (tree fndecl = cp_get_callee_fndecl_nofold (stmt)) > if (DECL_IMMEDIATE_FUNCTION_P (fndecl)) > { > gcc_assert (source_location_current_p (fndecl)); > --- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C.jj 2021-02-17 16:48:18.136421425 +0100 > +++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C 2021-02-17 16:49:55.929378398 +0100 > @@ -0,0 +1,13 @@ > +// PR c++/99132 > +// { dg-do compile { target c++11 } } > + > +template <class T> struct A { T c; }; > +template <class T> struct B { > + A<T> d; > + constexpr T operator-> () { return d.c; } > + B (B &&); > +}; > +struct C { > + virtual void foo (); > + void bar (B<C *> h) { h->foo (); } > +}; > > Jakub >
--- gcc/cp/cp-gimplify.c.jj 2021-02-17 16:14:42.621294819 +0100 +++ gcc/cp/cp-gimplify.c 2021-02-17 16:48:30.343291226 +0100 @@ -1386,7 +1386,7 @@ cp_genericize_r (tree *stmt_p, int *walk break; } - if (tree fndecl = cp_get_callee_fndecl (stmt)) + if (tree fndecl = cp_get_callee_fndecl_nofold (stmt)) if (DECL_IMMEDIATE_FUNCTION_P (fndecl)) { gcc_assert (source_location_current_p (fndecl)); --- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C.jj 2021-02-17 16:48:18.136421425 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C 2021-02-17 16:49:55.929378398 +0100 @@ -0,0 +1,13 @@ +// PR c++/99132 +// { dg-do compile { target c++11 } } + +template <class T> struct A { T c; }; +template <class T> struct B { + A<T> d; + constexpr T operator-> () { return d.c; } + B (B &&); +}; +struct C { + virtual void foo (); + void bar (B<C *> h) { h->foo (); } +};