This PR points out infinite looping in constexpr evaluation for e.g.
for (...)
{
continue;
while (1);
}
where we tried to evaluate the while despite the continue. The problem
started with r240591 and its cxx_eval_statement_list changes. This
patch fixes it by handling continue in such a way that we skip stmts that
are not meant to be evaluated.
Bootstrapped/regtested on x86_64-linux, ok for trunk/8.3?
2018-08-06 Marek Polacek <pola...@redhat.com>
PR c++/86767
* constexpr.c (cxx_eval_statement_list): Handle continue.
* g++.dg/cpp1y/constexpr-86767.C: New test.
diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index 365296d6e3b..79039ff2b79 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -3950,6 +3950,16 @@ cxx_eval_statement_list (const constexpr_ctx *ctx, tree
t,
for (i = tsi_start (t); !tsi_end_p (i); tsi_next (&i))
{
tree stmt = tsi_stmt (i);
+ /* We've found a continue, so skip everything until we reach
+ the label its jumping to. */
+ if (continues (jump_target))
+ {
+ if (label_matches (ctx, jump_target, stmt))
+ /* Found it. */
+ *jump_target = NULL_TREE;
+ else
+ continue;
+ }
if (TREE_CODE (stmt) == DEBUG_BEGIN_STMT)
continue;
r = cxx_eval_constant_expression (ctx, stmt, false,
diff --git gcc/testsuite/g++.dg/cpp1y/constexpr-86767.C
gcc/testsuite/g++.dg/cpp1y/constexpr-86767.C
index e69de29bb2d..2ad71d507d1 100644
--- gcc/testsuite/g++.dg/cpp1y/constexpr-86767.C
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-86767.C
@@ -0,0 +1,119 @@
+// PR c++/86767
+// { dg-do compile { target c++14 } }
+
+constexpr int
+fn0 () noexcept
+{
+ int r = 0;
+ for (int i = 0; i < 10; ++i)
+ {
+ continue;
+ r++;
+ for (int j = 0; j < 10; ++j )
+ {
+ }
+ }
+ return r;
+}
+static_assert (fn0 () == 0, "");
+
+constexpr int
+fn1 () noexcept
+{
+ int r = 0;
+ for (int i = 0; i < 10; ++i)
+ for (int j = 0; j < 10; ++j)
+ {
+ continue;
+ r++;
+ }
+ return r;
+}
+static_assert (fn1 () == 0, "");
+
+constexpr int
+fn2 () noexcept
+{
+ int r = 0;
+ for (int i = 0; i < 10; ++i)
+ {
+ continue;
+ r++;
+ }
+ return r;
+}
+static_assert (fn2 () == 0, "");
+
+constexpr int
+fn3 () noexcept
+{
+ int r = 0;
+ for (int i = 0; i < 10; ++i)
+ {
+ continue;
+ r++;
+ while (1)
+ {
+ }
+ }
+ return r;
+}
+static_assert (fn3 () == 0, "");
+
+constexpr int
+fn4 () noexcept
+{
+ for (int i = 0; i < 10; ++i)
+ {
+ switch (i)
+ {
+ case 5:
+ return i;
+ default:
+ continue;
+ }
+ while (1)
+ {
+ }
+ }
+ return 0;
+}
+static_assert (fn4 () == 5, "");
+
+constexpr int
+fn5 () noexcept
+{
+ for (int i = 0; i < 10; ++i)
+ {
+ switch (i)
+ {
+ case 0:
+ case 1:
+ case 2:
+ case 3:
+ case 4:
+ continue;
+ default:
+ return i;
+ }
+ while (1)
+ {
+ }
+ }
+ return 0;
+}
+static_assert (fn5 () == 5, "");
+
+constexpr int
+fn6 () noexcept
+{
+ int r = 0;
+ for (int i = 0; i < 10; ++i)
+ {
+ continue;
+ for (int j = 0; j < 10; ++j )
+ r++;
+ }
+ return r;
+}
+static_assert (fn6 () == 0, "");
Marek
