gcc/gcc11-pr98672.patch

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2021-01-15 Jakub Jelinek <jakub@redhat.com>
PR c++/98672
* constexpr.c (potential_constant_expression_1) <case FOR_STMT>,
<case WHILE_STMT>: If the condition isn't constant true, check if
the loop body can contain a return stmt.
* g++.dg/cpp1y/constexpr-98672.C: New test.
--- gcc/cp/constexpr.c.jj 2021-01-13 19:19:44.368469462 +0100
+++ gcc/cp/constexpr.c 2021-01-14 12:02:27.347042704 +0100
@@ -8190,7 +8190,17 @@ potential_constant_expression_1 (tree t,
/* If we couldn't evaluate the condition, it might not ever be
true. */
if (!integer_onep (tmp))
- return true;
+ {
+ /* Before returning true, check if the for body can contain
+ a return. */
+ hash_set<tree> pset;
+ check_for_return_continue_data data = { &pset, NULL_TREE };
+ if (tree ret_expr
+ = cp_walk_tree (&FOR_BODY (t), check_for_return_continue,
+ &data, &pset))
+ *jump_target = ret_expr;
+ return true;
+ }
}
if (!RECUR (FOR_EXPR (t), any))
return false;
@@ -8219,7 +8229,17 @@ potential_constant_expression_1 (tree t,
tmp = cxx_eval_outermost_constant_expr (tmp, true);
/* If we couldn't evaluate the condition, it might not ever be true. */
if (!integer_onep (tmp))
- return true;
+ {
+ /* Before returning true, check if the while body can contain
+ a return. */
+ hash_set<tree> pset;
+ check_for_return_continue_data data = { &pset, NULL_TREE };
+ if (tree ret_expr
+ = cp_walk_tree (&WHILE_BODY (t), check_for_return_continue,
+ &data, &pset))
+ *jump_target = ret_expr;
+ return true;
+ }
if (!RECUR (WHILE_BODY (t), any))
return false;
if (breaks (jump_target) || continues (jump_target))
--- gcc/testsuite/g++.dg/cpp1y/constexpr-98672.C.jj 2021-01-14 12:19:24.842438847 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-98672.C 2021-01-14 12:07:33.935551155 +0100
@@ -0,0 +1,35 @@
+// PR c++/98672
+// { dg-do compile { target c++14 } }
+
+void
+foo ()
+{
+}
+
+constexpr int
+bar ()
+{
+ for (int i = 0; i < 5; ++i)
+ return i;
+ foo ();
+ return 0;
+}
+
+constexpr int
+baz ()
+{
+ int i = 0;
+ while (i < 5)
+ {
+ if (i == 3)
+ return i;
+ else
+ ++i;
+ }
+ foo ();
+ return 0;
+}
+
+constexpr int i = bar ();
+constexpr int j = baz ();
+static_assert (i == 0 && j == 3, "");