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.
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?
2021-02-18 Jakub Jelinek <ja...@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
