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* [PATCH] c++: ICE with failed __is_constructible constraint [PR100474]
@ 2022-03-29 19:22 Patrick Palka
  2022-03-29 20:53 ` Jason Merrill
  0 siblings, 1 reply; 4+ messages in thread
From: Patrick Palka @ 2022-03-29 19:22 UTC (permalink / raw)
  To: gcc-patches

Here we're crashing when diagnosing a failed __is_constructible constraint
because diagnose_atomic_constraint don't know how to diagnose a trait
that diagnose_trait_expr doesn't specifically handle.  This patch fixes
this by falling through to the default case in this situation.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk and perhaps 11?

	PR c++/100474

gcc/cp/ChangeLog:

	* constraint.cc (diagnose_trait_expr): Rename to ...
	(maybe_diagnose_trait_expr): ... this.  Return a boolean
	indicating whether we handled the trait.
	(diagnose_atomic_constraint) <case TRAIT_EXPR>: Fall through to
	the default case if maybe_diagnose_trait_expr returns false.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-traits3.C: New test.
---
 gcc/cp/constraint.cc                          | 16 +++++++++-------
 gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C | 10 ++++++++++
 2 files changed, 19 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index c5a991b9e71..27b1b9bb659 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3567,10 +3567,10 @@ get_constraint_error_location (tree t)
   return input_location;
 }
 
-/* Emit a diagnostic for a failed trait.  */
+/* Maybe emit a friendlier diagnostic for the failed trait.  */
 
-static void
-diagnose_trait_expr (tree expr, tree args)
+static bool
+maybe_diagnose_trait_expr (tree expr, tree args)
 {
   location_t loc = cp_expr_location (expr);
 
@@ -3655,8 +3655,9 @@ diagnose_trait_expr (tree expr, tree args)
       inform (loc, "  %qT is not a union", t1);
       break;
     default:
-      gcc_unreachable ();
+      return false;
     }
+  return true;
 }
 
 /* Diagnose a substitution failure in the atomic constraint T using ARGS.  */
@@ -3685,9 +3686,6 @@ diagnose_atomic_constraint (tree t, tree args, tree result, sat_info info)
   STRIP_ANY_LOCATION_WRAPPER (expr);
   switch (TREE_CODE (expr))
     {
-    case TRAIT_EXPR:
-      diagnose_trait_expr (expr, args);
-      break;
     case REQUIRES_EXPR:
       gcc_checking_assert (info.diagnose_unsatisfaction_p ());
       /* Clear in_decl before replaying the substitution to avoid emitting
@@ -3696,6 +3694,10 @@ diagnose_atomic_constraint (tree t, tree args, tree result, sat_info info)
       info.in_decl = NULL_TREE;
       tsubst_requires_expr (expr, args, info);
       break;
+    case TRAIT_EXPR:
+      if (maybe_diagnose_trait_expr (expr, args))
+	break;
+      /* Fall through.  */
     default:
       if (!same_type_p (TREE_TYPE (result), boolean_type_node))
 	error_at (loc, "constraint %qE has type %qT, not %<bool%>",
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
new file mode 100644
index 00000000000..33152242988
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
@@ -0,0 +1,10 @@
+// PR c++/100474
+// { dg-do compile { target c++20 } }
+
+template<class T, class... Args>
+concept C = __is_constructible(T, Args...); // { dg-message "evaluated to 'false'" }
+struct S {
+  S() = delete;
+};
+
+static_assert(C<S>); // { dg-error "assert" }
-- 
2.35.1.677.gabf474a5dd


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-03-30 13:04 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-03-29 19:22 [PATCH] c++: ICE with failed __is_constructible constraint [PR100474] Patrick Palka
2022-03-29 20:53 ` Jason Merrill
2022-03-30 12:56   ` Patrick Palka
2022-03-30 13:03     ` Jason Merrill

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