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* [gcc r11-9456] c++: dependent bases and 'this' availability [PR103831]
@ 2022-01-12 17:03 Patrick Palka
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From: Patrick Palka @ 2022-01-12 17:03 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:614a9580d4463c4aefd74c40ed46bfab2bef65c7
commit r11-9456-g614a9580d4463c4aefd74c40ed46bfab2bef65c7
Author: Patrick Palka <ppalka@redhat.com>
Date: Tue Jan 11 13:00:48 2022 -0500
c++: dependent bases and 'this' availability [PR103831]
Here during satisfaction of B's constraints we're failing to reject the
object-less call to the non-static member function A::size ultimately
because satisfaction is performed in the (access) context of the class
template B, which has a dependent base, and so the any_dependent_bases_p
check within build_new_method_call causes us to not reject the call.
(Subsequent constexpr evaluation of the call succeeds since the function
is effectively static.)
This patch fixes this by refining the any_dependent_bases_p check within
build_new_method_call: if we're in a context where 'this' is unavailable,
then we cannot resolve the implicit object regardless of the presence of
a dependent base. So let's also check current_class_ptr alongside a_d_b_p.
PR c++/103831
gcc/cp/ChangeLog:
* call.c (build_new_method_call): Consider dependent bases only
if 'this' is available.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-class3.C: New test.
* g++.dg/template/non-dependent18.C: New test.
(cherry picked from commit 0378f563b0321c44c4a9c98cf46d2a22b9160f76)
Diff:
---
gcc/cp/call.c | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-class3.C | 12 ++++++++++++
gcc/testsuite/g++.dg/template/non-dependent18.C | 19 +++++++++++++++++++
3 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index a199ae9fa71..81b0d0f27ff 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -10793,7 +10793,7 @@ build_new_method_call_1 (tree instance, tree fns, vec<tree, va_gc> **args,
we know we really need it. */
cand->first_arg = instance;
}
- else if (any_dependent_bases_p ())
+ else if (current_class_ptr && any_dependent_bases_p ())
/* We can't tell until instantiation time whether we can use
*this as the implicit object argument. */;
else
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
new file mode 100644
index 00000000000..68b50b71278
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-class3.C
@@ -0,0 +1,12 @@
+// PR c++/103831
+// { dg-do compile { target c++20 } }
+
+struct A {
+ constexpr int size() { return 42; } // non-static
+};
+
+template<class T>
+ requires (T::size() == 42) // { dg-error "without object" }
+struct B : T { };
+
+template struct B<A>; // { dg-error "constraint" }
diff --git a/gcc/testsuite/g++.dg/template/non-dependent18.C b/gcc/testsuite/g++.dg/template/non-dependent18.C
new file mode 100644
index 00000000000..3e1556821a6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent18.C
@@ -0,0 +1,19 @@
+// PR c++/103831
+// { dg-do compile { target c++11 } }
+
+struct A {
+ constexpr int size() { return 42; } // non-static
+};
+
+template<class T>
+struct B : T {
+ static_assert(A::size() == 42, ""); // { dg-error "without object" }
+
+ static int f() {
+ static_assert(A::size() == 42, ""); // { dg-error "without object" }
+ return A::size(); // { dg-error "without object" }
+ }
+
+ int n = A::size();
+ static const int m = A::size(); // { dg-error "without object" }
+};
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