2019-11-27 Andrew Sutton <asutton@lock3software.com>

	PR c++/88395
	Prevent recursive satisfaction by adding requests to the instantiation
	stack.

gcc/cp/
	* constraint.cc (satisfy_declaration_constraints): Push tinst levels
	around satisfaction.

gcc/testsuite/
	* g++.dg/cpp2a/concepts-pr88395.C: New.
	* g++.dg/cpp2a/concepts-recursive-sat1.C: New.
	* g++.dg/cpp2a/concepts-recursive-sat2.C: New.
	* g++.dg/cpp2a/concepts-recursive-sat3.C: New.



git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@278773 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 68 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C b/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
new file mode 100644
index 00000000000..ad24da9cb47
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
@@ -0,0 +1,23 @@
+// { dg-do compile { target c++2a } }
+
+template <class T, class U>
+concept Concept2 = requires (T t, U u)
+{
+    t += u; // { dg-error "template instantiation depth" }
+};
+
+template <class T>
+concept Concept = Concept2 <T, T>;
+
+struct S
+{
+    template <Concept T>
+    constexpr S& operator += (T o);
+};
+
+constexpr S operator * (S a, S b)
+{
+    return a += b;
+}
+
+// { dg-prune-output "compilation terminated" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
new file mode 100644
index 00000000000..ee83d560cf6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat1.C
@@ -0,0 +1,18 @@
+// { dg-do compile { target c++2a } }
+
+template<int N, typename T>
+concept Foo = requires(T t) { foo<N + 1>(t); }; // { dg-error "template instantiation depth" }
+
+template<int N = 1, typename T = int>
+  requires Foo<N, T>
+int foo(T t)
+{
+  return foo<N + 1>(t);
+}
+
+int main(int, char**)
+{
+  return foo<1>(1);
+}
+
+// { dg-prune-output "compilation terminated" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat2.C b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat2.C
new file mode 100644
index 00000000000..d76f12eb209
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat2.C
@@ -0,0 +1,15 @@
+// { dg-do compile { target c++2a } }
+
+template<typename T>
+concept Fooable = requires(T t) { foo(t); }; // { dg-error "template instantiation depth" }
+
+template<Fooable T>
+void foo(T t) { }
+
+void test()
+{
+  struct S {} s;
+  foo(s);
+}
+
+// { dg-prune-output "compilation terminated" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat3.C
new file mode 100644
index 00000000000..b8ca9164792
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat3.C
@@ -0,0 +1,12 @@
+// { dg-do compile { target c++2a } }
+
+template<typename T>
+concept Fooable = requires(T t) { foo(t); };
+
+template<Fooable T>
+void foo(T t) { }
+
+void test()
+{
+  foo(0); // { dg-error "unsatisfied constraints" }
+}