From: Marek Polacek <polacek@redhat.com>
Date: Wed, 10 Oct 2018 21:11:18 +0000 (+0000)
Subject: PR c++/87567 - constexpr rejects call to non-constexpr function.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=8e9558f029123e00008d3ef464922128d018f0fc;p=gcc.git

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.

From-SVN: r265027
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 975f866c0b7..af8cb764139 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+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.
+
 2018-10-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/84423
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 403edda8c47..4fa8c965a9d 100644
--- a/gcc/cp/constexpr.c
+++ b/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 a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bbb47d379c0..5c751749491 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-10-10  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87567 - constexpr rejects call to non-constexpr function.
+	* g++.dg/cpp1y/constexpr-loop7.C: New test.
+
 2018-10-10  Paul A. Clarke  <pc@us.ibm.com>
 
 	PR target/87579
diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-loop7.C
new file mode 100644
index 00000000000..6733820fee2
--- /dev/null
+++ b/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;
+}