This patch further extends the satisfaction_cache class to diagnose
self-recursive satisfaction.
With this patch, a few more cmcstl2 tests fail at compile time due apparent
self-recursive satisfaction. I didn't analyze these failures
individually, but all errors contain view_interface::operator bool() in
their template instantiation backtrace, and applying a workaround
similar to PR97600#c3 to include/stl2/view/view_interface.hpp fixes all
observed failures. So I assume the fails are all due to the same latent
self-recursive satisfaction issue that r11-4584 fixed in libstdc++.
gcc/cp/ChangeLog:
* constraint.cc (sat_entry::evaluating): New member.
(satisfaction_cache::get): If entry->evaluating, diagnose
self-recursive satisfaction. Otherwise, set entry->evaluating
if we're not reusing a cached satisfaction result.
(satisfaction_cache::save): Clear entry->evaluating.
(satisfy_atom): Set up diagnosing_failed_constraint before the
first call to get().
gcc/testsuite/ChangeLog:
PR c++/96840
* g++.dg/cpp2a/concepts-pr88395.C: Adjust to expect the
self-recursive satisfaction to get directly diagnosed.
* g++.dg/cpp2a/concepts-recursive-sat2.C: Likewise.
* g++.dg/cpp2a/concepts-recursive-sat4.C: New test.
---
gcc/cp/constraint.cc | 39 +++++++++++++++----
gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C | 8 ++--
.../g++.dg/cpp2a/concepts-recursive-sat2.C | 6 +--
.../g++.dg/cpp2a/concepts-recursive-sat4.C | 13 +++++++
4 files changed, 49 insertions(+), 17 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index b98befaf71b..d1bffd598ef 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2428,6 +2428,11 @@ struct GTY((for_user)) sat_entry
We don't always want to do so, in order to avoid emitting duplicate
diagnostics in some cases. */
bool diagnose_instability;
+
+ /* True if we're in the middle of computing this satisfaction result.
+ Used to detect self-recursive satisfaction, during both quiet and
+ noisy satisfaction. */
+ bool evaluating;
};
struct sat_hasher : ggc_ptr_hash<sat_entry>
@@ -2581,6 +2586,7 @@ satisfaction_cache
mapping, we set this flag (in satisfy_atom) only if substitution
into its mapping previously failed. */
entry->diagnose_instability = true;
+ entry->evaluating = false;
*slot = entry;
}
else
@@ -2599,9 +2605,23 @@ satisfaction_cache::get ()
if (!entry)
return NULL_TREE;
- if (info.noisy () || entry->maybe_unstable)
- /* We're recomputing the satisfaction result from scratch. */
- return NULL_TREE;
+ if (entry->evaluating)
+ {
+ /* If we get here, it means satisfaction is self-recursive. */
+ gcc_checking_assert (!entry->result);
+ if (info.noisy ())
+ error_at (EXPR_LOCATION (ATOMIC_CONSTR_EXPR (entry->atom)),
+ "satisfaction of atomic constraint %qE depends on itself",
+ entry->atom);
+ return error_mark_node;
+ }
+
+ if (info.noisy () || entry->maybe_unstable || !entry->result)
+ {
+ /* We're computing the satisfaction result from scratch. */
+ entry->evaluating = true;
+ return NULL_TREE;
+ }
else
return entry->result;
}
@@ -2616,6 +2636,9 @@ satisfaction_cache::save (tree result)
if (!entry)
return result;
+ gcc_checking_assert (entry->evaluating);
+ entry->evaluating = false;
+
if (entry->result && result != entry->result)
{
if (info.quiet ())
@@ -2865,6 +2888,11 @@ static void diagnose_atomic_constraint (tree, tree,
tree, subst_info);
static tree
satisfy_atom (tree t, tree args, sat_info info)
{
+ /* In case there is a diagnostic, we want to establish the context
+ prior to printing errors. If no errors occur, this context is
+ removed before returning. */
+ diagnosing_failed_constraint failure (t, args, info.noisy ());
+
satisfaction_cache cache (t, args, info);
if (tree r = cache.get ())
return r;
@@ -2872,11 +2900,6 @@ satisfy_atom (tree t, tree args, sat_info info)
/* Perform substitution quietly. */
subst_info quiet (tf_none, NULL_TREE);
- /* In case there is a diagnostic, we want to establish the context
- prior to printing errors. If no errors occur, this context is
- removed before returning. */
- diagnosing_failed_constraint failure (t, args, info.noisy ());
-
/* Instantiate the parameter mapping. */
tree map = tsubst_parameter_mapping (ATOMIC_CONSTR_MAP (t), args, quiet);
if (map == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
index 1c25252d47b..e1792e19005 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr88395.C
@@ -1,9 +1,9 @@
// { dg-do compile { target c++20 } }
template <class T, class U>
-concept Concept2 = requires (T t, U u)
+concept Concept2 = requires (T t, U u) // { dg-error "depends on itself" }
{
- t += u; // { dg-error "template instantiation depth" }
+ t += u;
};
template <class T>
@@ -17,7 +17,5 @@ struct S
constexpr S operator * (S a, S b)
{
- return a += b;
+ return a += b; // { dg-error "no match" }
}
-
-// { 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
index 992fcbbfccb..9bc96f58979 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat2.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat2.C
@@ -1,7 +1,7 @@
// { dg-do compile { target c++20 } }
template<typename T>
-concept Fooable = requires(T t) { foo(t); }; // { dg-error "template
instantiation depth" }
+concept Fooable = requires(T t) { foo(t); }; // { dg-error "depends on itself"
}
template<Fooable T>
void foo(T t) { }
@@ -9,7 +9,5 @@ void foo(T t) { }
void test()
{
struct S {} s;
- foo(s);
+ foo(s); // { dg-error "no match" }
}
-
-// { dg-prune-output "compilation terminated" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C
new file mode 100644
index 00000000000..18d126e05ea
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C
@@ -0,0 +1,13 @@
+// PR c++/96840
+// { dg-do compile { target c++20 } }
+
+template <class T, class U> concept C = requires(T t, U u) { t * u; };
+// { dg-message "required for the satisfaction of 'C<T, Rep>' .with T =
Int<int>; Rep = int." "" { target *-*-* } .-1 }
+// { dg-error "depends on itself" "" { target *-*-* } .-2 }
+
+template <class Rep> struct Int {
+ template <class T> requires C<T, Rep> friend void operator*(T, Int) { }
+ template <class T> requires C<T, Rep> friend void operator*(Int, T) { }
+};
+
+void f() { 0 * Int<int>{}; }
--
2.29.2.404.ge67fbf927d
