On Thu, Jan 17, 2019 at 04:17:29PM -0500, Jason Merrill wrote:
> On 1/17/19 2:09 PM, Marek Polacek wrote:
> > This patch ought to fix the rest of 78244, a missing narrowing warning in
> > decltype.
> >
> > As I explained in Bugzilla, there can be three scenarios:
> >
> > 1) decltype is in a template and it has no dependent expressions, which
> > is the problematical case. finish_compound_literal just returns the
> > compound literal without checking narrowing if processing_template_decl.
>
> This is the sort of thing that we've been gradually fixing: if the compound
> literal isn't dependent at all, we want to do the normal processing. And
> then usually return a result based on the original trees rather than the
> result of processing. For instance, finish_call_expr. Something like that
> ought to work here, too, and be more generally applicable; this shouldn't be
> limited to casting to a scalar type, casting to a known class type can also
> involve narrowing.
Great, that works just fine. I also had to check if the type is
type-dependent, otherwise complete_type could fail.
> The check in the other patch that changes instantiation_dependent_r should
> be more similar to the one in finish_compound_literal. Or perhaps you could
> set a flag here in finish_compound_literal to indicate that it's
> instantiation-dependent, and just check that in instantiation_dependent_r.
Done, but I feel bad about adding another flag. But I guess it's cheaper
this way. Thanks!
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2019-01-18 Marek Polacek <pola...@redhat.com>
PR c++/88815 - narrowing conversion lost in decltype.
PR c++/78244 - narrowing conversion in template not detected.
* cp-tree.h (CONSTRUCTOR_IS_DEPENDENT): New.
* pt.c (instantiation_dependent_r): Consider a CONSTRUCTOR with
CONSTRUCTOR_IS_DEPENDENT instantiation-dependent.
* semantics.c (finish_compound_literal): When the compound literal
isn't instantiation-dependent and the type isn't type-dependent,
fall back to the normal processing. Don't only call check_narrowing
for scalar types. Set CONSTRUCTOR_IS_DEPENDENT.
* g++.dg/cpp0x/Wnarrowing15.C: New test.
* g++.dg/cpp0x/constexpr-decltype3.C: New test.
* g++.dg/cpp1y/Wnarrowing1.C: New test.
diff --git gcc/cp/cp-tree.h gcc/cp/cp-tree.h
index 5cc8f88d522..778874cccd6 100644
--- gcc/cp/cp-tree.h
+++ gcc/cp/cp-tree.h
@@ -424,6 +424,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
DECL_FINAL_P (in FUNCTION_DECL)
QUALIFIED_NAME_IS_TEMPLATE (in SCOPE_REF)
DECLTYPE_FOR_INIT_CAPTURE (in DECLTYPE_TYPE)
+ CONSTRUCTOR_IS_DEPENDENT (in CONSTRUCTOR)
TINFO_USED_TEMPLATE_ID (in TEMPLATE_INFO)
PACK_EXPANSION_SIZEOF_P (in *_PACK_EXPANSION)
OVL_USING_P (in OVERLOAD)
@@ -4202,6 +4203,11 @@ more_aggr_init_expr_args_p (const
aggr_init_expr_arg_iterator *iter)
B b{1,2}, not B b({1,2}) or B b = {1,2}. */
#define CONSTRUCTOR_IS_DIRECT_INIT(NODE) (TREE_LANG_FLAG_0 (CONSTRUCTOR_CHECK
(NODE)))
+/* True if this CONSTRUCTOR is instantiation-dependent and needs to be
+ substituted. */
+#define CONSTRUCTOR_IS_DEPENDENT(NODE) \
+ (TREE_LANG_FLAG_1 (CONSTRUCTOR_CHECK (NODE)))
+
/* True if this CONSTRUCTOR should not be used as a variable initializer
because it was loaded from a constexpr variable with mutable fields. */
#define CONSTRUCTOR_MUTABLE_POISON(NODE) \
diff --git gcc/cp/pt.c gcc/cp/pt.c
index e4f76478f54..ae77bae6b29 100644
--- gcc/cp/pt.c
+++ gcc/cp/pt.c
@@ -25800,6 +25800,11 @@ instantiation_dependent_r (tree *tp, int
*walk_subtrees,
return *tp;
break;
+ case CONSTRUCTOR:
+ if (CONSTRUCTOR_IS_DEPENDENT (*tp))
+ return *tp;
+ break;
+
default:
break;
}
diff --git gcc/cp/semantics.c gcc/cp/semantics.c
index e654750d249..4ff09ad3fb7 100644
--- gcc/cp/semantics.c
+++ gcc/cp/semantics.c
@@ -2795,11 +2795,14 @@ finish_compound_literal (tree type, tree
compound_literal,
return error_mark_node;
}
- if (processing_template_decl)
+ if (instantiation_dependent_expression_p (compound_literal)
+ || dependent_type_p (type))
{
TREE_TYPE (compound_literal) = type;
/* Mark the expression as a compound literal. */
TREE_HAS_CONSTRUCTOR (compound_literal) = 1;
+ /* And as instantiation-dependent. */
+ CONSTRUCTOR_IS_DEPENDENT (compound_literal) = true;
if (fcl_context == fcl_c99)
CONSTRUCTOR_C99_COMPOUND_LITERAL (compound_literal) = 1;
return compound_literal;
@@ -2822,8 +2825,7 @@ finish_compound_literal (tree type, tree compound_literal,
&& check_array_initializer (NULL_TREE, type, compound_literal))
return error_mark_node;
compound_literal = reshape_init (type, compound_literal, complain);
- if (SCALAR_TYPE_P (type)
- && !BRACE_ENCLOSED_INITIALIZER_P (compound_literal)
+ if (!BRACE_ENCLOSED_INITIALIZER_P (compound_literal)
&& !check_narrowing (type, compound_literal, complain))
return error_mark_node;
if (TREE_CODE (type) == ARRAY_TYPE
diff --git gcc/testsuite/g++.dg/cpp0x/Wnarrowing15.C
gcc/testsuite/g++.dg/cpp0x/Wnarrowing15.C
new file mode 100644
index 00000000000..4e7c17dcfca
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/Wnarrowing15.C
@@ -0,0 +1,14 @@
+// PR c++/78244
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+auto f1() -> decltype(int{2.0}, void()) { } // { dg-error "narrowing
conversion" }
+
+template <typename T>
+auto f2() -> decltype(int{2.0}) { return 1; } // { dg-error "narrowing
conversion" }
+
+template <typename T>
+auto f3() -> decltype(void(), int{2.0}) { return 1; } // { dg-error "narrowing
conversion" }
+
+template <typename T>
+auto f4() -> decltype((int{2.0})) { return 1; } // { dg-error "narrowing
conversion" }
diff --git gcc/testsuite/g++.dg/cpp0x/constexpr-decltype3.C
gcc/testsuite/g++.dg/cpp0x/constexpr-decltype3.C
new file mode 100644
index 00000000000..fd05366de50
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-decltype3.C
@@ -0,0 +1,25 @@
+// PR c++/88815
+// { dg-do compile { target c++11 } }
+
+struct true_type {
+ constexpr operator bool() const { return true; }
+};
+
+struct false_type {
+ constexpr operator bool() const { return false; }
+};
+
+template<int (*p)()>
+true_type is_constexpr_impl(decltype(int{(p(), 0U)}));
+
+template<int (*p)()>
+false_type is_constexpr_impl(...);
+
+template<int (*p)()>
+using is_constexpr = decltype(is_constexpr_impl<p>(0));
+
+constexpr int f() { return 0; }
+int g() { return 0; }
+
+static_assert(is_constexpr<f>(), "");
+static_assert(!is_constexpr<g>(), "");
diff --git gcc/testsuite/g++.dg/cpp1y/Wnarrowing1.C
gcc/testsuite/g++.dg/cpp1y/Wnarrowing1.C
new file mode 100644
index 00000000000..e1e499542f0
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp1y/Wnarrowing1.C
@@ -0,0 +1,5 @@
+// PR c++/78244
+// { dg-do compile { target c++14 } }
+
+template<typename>
+decltype(int{1.1}) v; // { dg-error "narrowing conversion" }
