From d49318d9bc3e63251aada27b322e7756eab19884 Mon Sep 17 00:00:00 2001

From: Paolo Carlini <paolo.carlini@oracle.com>

Date: Tue, 5 Sep 2017 13:33:44 +0000

Subject: [PATCH] re PR c++/81942 (ICE on empty constexpr constructor with

 C++14)

/cp

2017-09-05  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81942

	* cp-tree.h (LABEL_DECL_CDTOR): Add and document.

	* decl.c (start_preparsed_function): Set LABEL_DECL_CDTOR when

	creating cdtor_label.

	* constexpr.c (returns): Add the case of a constructor/destructor

	returning via a LABEL_DECL_CDTOR label.

	(cxx_eval_constant_expression, case [GOTO_EXPR]): Likewise.

/testsuite

2017-09-05  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81942

	* g++.dg/cpp1y/constexpr-return3.C: New.

From-SVN: r251714

---

 gcc/cp/ChangeLog                               | 10 ++++++++++

 gcc/cp/constexpr.c                             |  8 ++++++--

 gcc/cp/cp-tree.h                               |  6 ++++++

 gcc/cp/decl.c                                  |  5 ++++-

 gcc/testsuite/ChangeLog                        |  5 +++++

 gcc/testsuite/g++.dg/cpp1y/constexpr-return3.C | 11 +++++++++++

 6 files changed, 42 insertions(+), 3 deletions(-)

 create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-return3.C

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c

index f3e868cff02..a5692fb3b3a 100644

--- a/gcc/cp/constexpr.c

+++ b/gcc/cp/constexpr.c

@@ -3671,7 +3671,9 @@ static bool

 returns (tree *jump_target)

 {

   return *jump_target

-    && TREE_CODE (*jump_target) == RETURN_EXPR;

+    && (TREE_CODE (*jump_target) == RETURN_EXPR

+	|| (TREE_CODE (*jump_target) == LABEL_DECL

+	    && LABEL_DECL_CDTOR (*jump_target)));

 }

 static bool

@@ -4554,7 +4556,9 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,

     case GOTO_EXPR:

       *jump_target = TREE_OPERAND (t, 0);

-      gcc_assert (breaks (jump_target) || continues (jump_target));

+      gcc_assert (breaks (jump_target) || continues (jump_target)

+		  /* Allow for jumping to a cdtor_label.  */

+		  || returns (jump_target));

       break;

     case LOOP_EXPR:

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h

index 432faa9da14..7dc20b1649b 100644

--- a/gcc/cp/cp-tree.h

+++ b/gcc/cp/cp-tree.h

@@ -456,6 +456,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];

       DECL_CONSTRAINT_VAR_P (in a PARM_DECL)

       TEMPLATE_DECL_COMPLEX_ALIAS_P (in TEMPLATE_DECL)

       DECL_INSTANTIATING_NSDMI_P (in a FIELD_DECL)

+      LABEL_DECL_CDTOR (in LABEL_DECL)

    3: DECL_IN_AGGR_P.

    4: DECL_C_BIT_FIELD (in a FIELD_DECL)

       DECL_ANON_UNION_VAR_P (in a VAR_DECL)

@@ -3833,6 +3834,11 @@ more_aggr_init_expr_args_p (const aggr_init_expr_arg_iterator *iter)

 #define LABEL_DECL_CONTINUE(NODE) \

   DECL_LANG_FLAG_1 (LABEL_DECL_CHECK (NODE))

+/* Nonzero if NODE is the target for genericization of 'return' stmts

+   in constructors/destructors of targetm.cxx.cdtor_returns_this targets.  */

+#define LABEL_DECL_CDTOR(NODE) \

+  DECL_LANG_FLAG_2 (LABEL_DECL_CHECK (NODE))

+

 /* True if NODE was declared with auto in its return type, but it has

    started compilation and so the return type might have been changed by

    return type deduction; its declared return type should be found in

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c

index d6b80c604c8..861dfcfd828 100644

--- a/gcc/cp/decl.c

+++ b/gcc/cp/decl.c

@@ -15072,7 +15072,10 @@ start_preparsed_function (tree decl1, tree attrs, int flags)

   if (DECL_DESTRUCTOR_P (decl1)

       || (DECL_CONSTRUCTOR_P (decl1)

 	  && targetm.cxx.cdtor_returns_this ()))

-    cdtor_label = create_artificial_label (input_location);

+    {

+      cdtor_label = create_artificial_label (input_location);

+      LABEL_DECL_CDTOR (cdtor_label) = true;

+    }

   start_fname_decls ();

diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-return3.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-return3.C

new file mode 100644

index 00000000000..4cf4128e9eb

--- /dev/null

+++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-return3.C

@@ -0,0 +1,11 @@

+// PR c++/81942

+// { dg-do compile { target c++14 } }

+

+class A {

+public:

+    constexpr A() {

+      return;

+    }

+};

+

+A mwi;

-- 

2.18.4