C++ PATCH for c++/82115, ICE with variable initialized to own address

[Jason Merrill]

In this testcase, we consider the initializer of b to decide if it's
value-dependent, but the initializer mentions b, so we were recursing
infinitely.  But if we're interested in the address, we don't care
about the value; we already handle that appropriately in the constexpr
code, this patch updates value_dependent_expression_p accordingly.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit c7321d4e2c36f6e336cfa1eb27c4f5434e9dd349
Author: Jason Merrill <ja...@redhat.com>
Date:   Wed Dec 6 15:27:33 2017 -0500

            PR c++/82115 - ICE with variable initialized with its own address.
    
            * pt.c (value_dependent_expression_p): Add lval parameter.  Don't
            consider DECL_INITIAL if it's true.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index e77241f3d97..575255d64e7 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6542,7 +6542,7 @@ extern bool type_dependent_object_expression_p    (tree);
 extern bool any_type_dependent_arguments_p      (const vec<tree, va_gc> *);
 extern bool any_type_dependent_elements_p       (const_tree);
 extern bool type_dependent_expression_p_push   (tree);
-extern bool value_dependent_expression_p       (tree);
+extern bool value_dependent_expression_p       (tree, bool = false);
 extern bool instantiation_dependent_expression_p (tree);
 extern bool instantiation_dependent_uneval_expression_p (tree);
 extern bool any_value_dependent_elements_p      (const_tree);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 685f34a735d..252712e80f2 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -23916,7 +23916,7 @@ instantiation_dependent_scope_ref_p (tree t)
    can be tested for value dependence.  */
 
 bool
-value_dependent_expression_p (tree expression)
+value_dependent_expression_p (tree expression, bool lval /* = false */)
 {
   if (!processing_template_decl || expression == NULL_TREE)
     return false;
@@ -23950,6 +23950,7 @@ value_dependent_expression_p (tree expression)
       /* A non-type template parm.  */
       if (DECL_TEMPLATE_PARM_P (expression))
        return true;
+      gcc_checking_assert (!lval);
       return value_dependent_expression_p (DECL_INITIAL (expression));
 
     case VAR_DECL:
@@ -23959,7 +23960,8 @@ value_dependent_expression_p (tree expression)
           Note that a non-dependent parenthesized initializer will have
           already been replaced with its constant value, so if we see
           a TREE_LIST it must be dependent.  */
-      if (DECL_INITIAL (expression)
+      if (!lval
+         && DECL_INITIAL (expression)
          && decl_constant_var_p (expression)
          && (TREE_CODE (DECL_INITIAL (expression)) == TREE_LIST
              /* cp_finish_decl doesn't fold reference initializers.  */
@@ -23969,7 +23971,7 @@ value_dependent_expression_p (tree expression)
       if (DECL_HAS_VALUE_EXPR_P (expression))
        {
          tree value_expr = DECL_VALUE_EXPR (expression);
-         if (value_dependent_expression_p (value_expr))
+         if (value_dependent_expression_p (value_expr, lval))
            return true;
        }
       return false;
@@ -24005,7 +24007,7 @@ value_dependent_expression_p (tree expression)
        if (TREE_CODE (expression) == TREE_LIST)
          return any_value_dependent_elements_p (expression);
 
-       return value_dependent_expression_p (expression);
+       return value_dependent_expression_p (expression, lval);
       }
 
     case SIZEOF_EXPR:
@@ -24039,7 +24041,7 @@ value_dependent_expression_p (tree expression)
       return instantiation_dependent_scope_ref_p (expression);
 
     case COMPONENT_REF:
-      return (value_dependent_expression_p (TREE_OPERAND (expression, 0))
+      return (value_dependent_expression_p (TREE_OPERAND (expression, 0), lval)
              || value_dependent_expression_p (TREE_OPERAND (expression, 1)));
 
     case NONTYPE_ARGUMENT_PACK:
@@ -24087,7 +24089,7 @@ value_dependent_expression_p (tree expression)
     case ADDR_EXPR:
       {
        tree op = TREE_OPERAND (expression, 0);
-       return (value_dependent_expression_p (op)
+       return (value_dependent_expression_p (op, true)
                || has_value_dependent_address (op));
       }
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-self1.C 
b/gcc/testsuite/g++.dg/cpp0x/constexpr-self1.C
new file mode 100644
index 00000000000..96f1d18146a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-self1.C
@@ -0,0 +1,14 @@
+// PR c++/82115
+// { dg-do compile { target c++11 } }
+
+struct A { int const u = 0; };
+
+struct B : A
+{ 
+  constexpr B (int const *p) : v (p) {}
+  int const *v;
+};
+
+constexpr B b (&b.u);
+
+template < typename > void foo () { b; }