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C++ PATCH for c++/87567, constexpr rejects call to non-constexpr function
- From: Marek Polacek <polacek at redhat dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>, Jason Merrill <jason at redhat dot com>
- Date: Wed, 10 Oct 2018 11:58:50 -0400
- Subject: C++ PATCH for c++/87567, constexpr rejects call to non-constexpr function
In this testcase, the call to f() can never be a constant expression, but
that's not a problem because it is never reached. We handle a similar scenario
for IF_STMT, so we can just do the same. The RANGE_FOR_STMT case seems to
never be reached in the whole testsuite, so I didn't change that.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2018-10-10 Marek Polacek <polacek@redhat.com>
PR c++/87567 - constexpr rejects call to non-constexpr function.
* constexpr.c (potential_constant_expression_1) <case FOR_STMT>: Return
true if the condition is always false.
<case WHILE_STMT>: Likewise.
* g++.dg/cpp1y/constexpr-loop7.C: New test.
diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index 403edda8c47..4fa8c965a9d 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -5818,8 +5818,16 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
case FOR_STMT:
if (!RECUR (FOR_INIT_STMT (t), any))
return false;
- if (!RECUR (FOR_COND (t), rval))
+ tmp = FOR_COND (t);
+ if (!RECUR (tmp, rval))
return false;
+ if (tmp)
+ {
+ if (!processing_template_decl)
+ tmp = cxx_eval_outermost_constant_expr (tmp, true);
+ if (integer_zerop (tmp))
+ return true;
+ }
if (!RECUR (FOR_EXPR (t), any))
return false;
if (!RECUR (FOR_BODY (t), any))
@@ -5840,8 +5848,13 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
return true;
case WHILE_STMT:
- if (!RECUR (WHILE_COND (t), rval))
+ tmp = WHILE_COND (t);
+ if (!RECUR (tmp, rval))
return false;
+ if (!processing_template_decl)
+ tmp = cxx_eval_outermost_constant_expr (tmp, true);
+ if (integer_zerop (tmp))
+ return true;
if (!RECUR (WHILE_BODY (t), any))
return false;
if (breaks (jump_target) || continues (jump_target))
diff --git gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C
index e69de29bb2d..6733820fee2 100644
--- gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C
@@ -0,0 +1,21 @@
+// PR c++/87567
+// { dg-do compile { target c++14 } }
+
+constexpr bool always_false() { return false; }
+int f() { return 1; }
+
+constexpr int
+fn1 ()
+{
+ while (always_false ())
+ return f();
+ return 0;
+}
+
+constexpr int
+fn2 ()
+{
+ for (;always_false();)
+ return f();
+ return 0;
+}