On Mon, Mar 02, 2020 at 05:50:01PM -0500, Jason Merrill wrote:
On 2/29/20 2:32 PM, Marek Polacek wrote:
The point of this patch is to fix the recurring problem of trees
generated by convert_like while processing a template that break when
substituting. For instance, when convert_like creates a CALL_EXPR
while in a template, substituting such a call breaks in finish_call_expr
because we have two 'this' arguments. Another problem is that we
can create &TARGET_EXPR<> and then fail when substituting because we're
taking the address of an rvalue. I've analyzed some of the already fixed
PRs and also some of the currently open ones:
In c++/93870 we create EnumWrapper<E>::operator E(&operator~(E)).
In c++/87145 we create S::operator int (&{N}).
In c++/92031 we create &TARGET_EXPR <0>.
And so on. I'd like to fix it once and for all. I wanted something
that fixes all the existing cases, removes the ugly check in
convert_nontype_argument, and something suitable for stage4. I.e.,
I didn't implement any cleanups suggested in
<https://gcc.gnu.org/ml/gcc-patches/2020-02/msg00832.html> regarding
the pattern in e.g. build_explicit_specifier.
Hmm, it seems to me that addressing that pattern is an important part of
fixing this once and for all.
The gist of the problem is when convert_like_real creates a call for
a ck_user or wraps a TARGET_EXPR in & in a template. So in these cases
use IMPLICIT_CONV_EXPR. In a template we shouldn't need to perform the
actual conversion, we only need it's result type. Is that something
that convert_like_real shouldn't do?
perform_direct_initialization_if_possible and perform_implicit_conversion_flags
can also create an IMPLICIT_CONV_EXPR.
This seems like a reasonable approach.
Great.
Given the change above, build_converted_constant_expr can return an
IMPLICIT_CONV_EXPR so call fold_non_dependent_expr rather than
maybe_constant_value to deal with that. A problem with that is that now
we may instantiate something twice in a row (?).
Right, and we must not do that.
Ack.
Handling all of it in
build_converted_constant_expr won't be that straightforward because we
sometimes call cxx_constant_value to give errors, or use manifestly_const_eval
which should be honored.
Fair enough. The alternative is ensuring that it's OK to call
build_converted_constant_expr when processing_template_decl is true, and
that the result in that case is still template trees. I think that's what
you are doing.
With this approach, we can change
expr = instantiate_non_dependent_expr_sfinae (expr, complain);
/* Don't let convert_like_real create more template codes. */
processing_template_decl_sentinel s;
expr = build_converted_constant_bool_expr (expr, complain);
expr = cxx_constant_value (expr);
to
expr = build_converted_constant_bool_expr (expr, complain);
expr = instantiate_non_dependent_expr_sfinae (expr, complain);
expr = cxx_constant_value (expr);
Yes?
Yes, that seems to work. Changed in this patch per the above.
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7383,6 +7383,12 @@ convert_like_real (conversion *convs, tree expr, tree
fn, int argnum,
{
struct z_candidate *cand = convs->cand;
+ /* Creating &TARGET_EXPR<> in a template breaks when substituting,
+ and creating a CALL_EXPR in a template breaks in finish_call_expr
+ so use an IMPLICIT_CONV_EXPR for this conversion. */
+ if (processing_template_decl)
+ return build1 (IMPLICIT_CONV_EXPR, totype, expr);
+
if (cand == NULL)
/* We chose the surrogate function from add_conv_candidate, now we
actually need to build the conversion. */
@@ -7760,6 +7766,12 @@ convert_like_real (conversion *convs, tree expr, tree
fn, int argnum,
expr = convert_bitfield_to_declared_type (expr);
expr = fold_convert (type, expr);
}
+
+ /* Creating &TARGET_EXPR<> in a template would break when
+ tsubsting the expression, so use an IMPLICIT_CONV_EXPR
+ instead. */
+ if (processing_template_decl)
+ return build1 (IMPLICIT_CONV_EXPR, totype, expr);
expr = build_target_expr_with_type (expr, type, complain);
}
Don't you need the same thing for ck_list, ck_aggr, ck_base? Is there a
reason not to do this in one place for anything other than ck_identity, at
least if a class type is involved?
I didn't think I needed it because it didn't look like we might create either
&TARGET_EXPR or CALL_EXPR there. But maybe it'd be safer to do it even for
ck_list, ck_aggr, ck_base, so changed.
But the ck_ref_bind hunk had to stay: we can create a TARGET_EXPR even when
there's no class involved in the conversion, e.g. converting and integer to
a reference type, when a temporary is needed.
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index e3f4b435a49..d04b042f880 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10281,8 +10281,8 @@ compute_array_index_type_loc (location_t name_loc, tree
name, tree size,
/* Pedantically a constant expression is required here and so
__builtin_is_constant_evaluated () should fold to true if it
is successfully folded into a constant. */
- size = maybe_constant_value (size, NULL_TREE,
- /*manifestly_const_eval=*/true);
+ size = fold_non_dependent_expr (size, complain,
+ /*manifestly_const_eval=*/true);
Here's that broken double-instantiation. Does it work if you also remove
the instantiate_non_dependent_expr before the call to
build_converted_constant_expr?
Yes! Since this code here is guarded with !type_dependent_expression_p,
I was wondering what would happen when we have a value-dependent expression;
added new test for that. fold_non_dependent_expr_template will see that the
expr is not is_nondependent_constant_expression, so it just returns it, it's
not TREE_CONSTANT, so we use origsize.
Meanwhile, PR94068 was opened, another instance of this problem. New test
added.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
-- >8 --
The point of this patch is to fix the recurring problem of trees
generated by convert_like while processing a template that break when
substituting. For instance, when convert_like creates a CALL_EXPR
while in a template, substituting such a call breaks in finish_call_expr
because we have two 'this' arguments. Another problem is that we
can create &TARGET_EXPR<> and then fail when substituting because we're
taking the address of an rvalue. I've analyzed some of the already fixed
PRs and also some of the currently open ones:
In c++/93870 we create EnumWrapper<E>::operator E(&operator~(E)).
In c++/87145 we create S::operator int (&{N}).
In c++/92031 we create &TARGET_EXPR <0>.
The gist of the problem is when convert_like_real creates a call for
a ck_user or wraps a TARGET_EXPR in & in a template. So in these cases
use IMPLICIT_CONV_EXPR. In a template we shouldn't need to perform the
actual conversion, we only need it's result type.
perform_direct_initialization_if_possible and
perform_implicit_conversion_flags can also create an IMPLICIT_CONV_EXPR.
Given the change above, build_converted_constant_expr can return an
IMPLICIT_CONV_EXPR so call fold_non_dependent_expr rather than
maybe_constant_value to deal with that.
To avoid the problem of instantiating something twice in a row I'm
removing a call to instantiate_non_dependent_expr_sfinae in
compute_array_index_type_loc. And the build_converted_constant_expr
pattern can now be simplified.
2020-03-09 Marek Polacek <pola...@redhat.com>
PR c++/92031 - bogus taking address of rvalue error.
PR c++/91465 - ICE with template codes in check_narrowing.
PR c++/93870 - wrong error when converting template non-type arg.
PR c++/94068 - ICE with template codes in check_narrowing.
* call.c (convert_like_real): Return IMPLICIT_CONV_EXPR
in a template when not ck_identity and we're dealing with a class.
(convert_like_real) <case ck_ref_bind>: Return IMPLICIT_CONV_EXPR
in a template if we need a temporary.
* decl.c (compute_array_index_type_loc): Remove
instantiate_non_dependent_expr_sfinae call. Call
fold_non_dependent_expr instead of maybe_constant_value.
(build_explicit_specifier): Don't instantiate or create a sentinel
before converting the expression.
* except.c (build_noexcept_spec): Likewise.
* pt.c (convert_nontype_argument): Don't build IMPLICIT_CONV_EXPR.
Set IMPLICIT_CONV_EXPR_NONTYPE_ARG if that's what
build_converted_constant_expr returned.
* typeck2.c (check_narrowing): Call fold_non_dependent_expr instead
of maybe_constant_value.
* g++.dg/cpp0x/conv-tmpl2.C: New test.
* g++.dg/cpp0x/conv-tmpl3.C: New test.
* g++.dg/cpp0x/conv-tmpl4.C: New test.
* g++.dg/cpp0x/conv-tmpl5.C: New test.
* g++.dg/cpp0x/conv-tmpl6.C: New test.
* g++.dg/cpp1z/conv-tmpl1.C: New test.
---
gcc/cp/call.c | 18 ++++++++++++++
gcc/cp/decl.c | 9 +++----
gcc/cp/except.c | 4 +--
gcc/cp/pt.c | 25 ++++---------------
gcc/cp/typeck2.c | 6 ++++-
gcc/testsuite/g++.dg/cpp0x/conv-tmpl2.C | 21 ++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/conv-tmpl3.C | 16 ++++++++++++
gcc/testsuite/g++.dg/cpp0x/conv-tmpl4.C | 33 +++++++++++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/conv-tmpl5.C | 13 ++++++++++
gcc/testsuite/g++.dg/cpp0x/conv-tmpl6.C | 16 ++++++++++++
gcc/testsuite/g++.dg/cpp1z/conv-tmpl1.C | 10 ++++++++
11 files changed, 141 insertions(+), 30 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/conv-tmpl2.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/conv-tmpl3.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/conv-tmpl4.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/conv-tmpl5.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/conv-tmpl6.C
create mode 100644 gcc/testsuite/g++.dg/cpp1z/conv-tmpl1.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index c0340d96f3c..5767a8b8c4e 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7377,6 +7377,16 @@ convert_like_real (conversion *convs, tree expr, tree
fn, int argnum,
if (issue_conversion_warnings && (complain & tf_warning))
conversion_null_warnings (totype, expr, fn, argnum);
+ /* Creating &TARGET_EXPR<> in a template breaks when substituting,
+ and creating a CALL_EXPR in a template breaks in finish_call_expr
+ so use an IMPLICIT_CONV_EXPR for this conversion. We would have
+ created such codes e.g. when calling a user-defined conversion
+ function. */
+ if (processing_template_decl
+ && convs->kind != ck_identity
+ && (CLASS_TYPE_P (totype) || CLASS_TYPE_P (TREE_TYPE (expr))))
+ return build1 (IMPLICIT_CONV_EXPR, totype, expr);
+
switch (convs->kind)
{
case ck_user:
@@ -7763,6 +7773,14 @@ convert_like_real (conversion *convs, tree expr, tree
fn, int argnum,
expr = convert_bitfield_to_declared_type (expr);
expr = fold_convert (type, expr);
}
+
+ /* Creating &TARGET_EXPR<> in a template would break when
+ tsubsting the expression, so use an IMPLICIT_CONV_EXPR
+ instead. This can happen even when there's no class
+ involved, e.g., when converting an integer to a reference
+ type. */
+ if (processing_template_decl)
+ return build1 (IMPLICIT_CONV_EXPR, totype, expr);
expr = build_target_expr_with_type (expr, type, complain);
}
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index e3f4b435a49..bb242743074 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10276,13 +10276,12 @@ compute_array_index_type_loc (location_t name_loc,
tree name, tree size,
NOP_EXPR with TREE_SIDE_EFFECTS; don't fold in that case. */;
else
{
- size = instantiate_non_dependent_expr_sfinae (size, complain);
size = build_converted_constant_expr (size_type_node, size, complain);
/* Pedantically a constant expression is required here and so
__builtin_is_constant_evaluated () should fold to true if it
is successfully folded into a constant. */
- size = maybe_constant_value (size, NULL_TREE,
- /*manifestly_const_eval=*/true);
+ size = fold_non_dependent_expr (size, complain,
+ /*manifestly_const_eval=*/true);
if (!TREE_CONSTANT (size))
size = origsize;
@@ -17607,10 +17606,8 @@ build_explicit_specifier (tree expr, tsubst_flags_t
complain)
/* Wait for instantiation, tsubst_function_decl will handle it. */
return expr;
- expr = instantiate_non_dependent_expr_sfinae (expr, complain);
- /* Don't let convert_like_real create more template codes. */
- processing_template_decl_sentinel s;
expr = build_converted_constant_bool_expr (expr, complain);
+ expr = instantiate_non_dependent_expr_sfinae (expr, complain);
expr = cxx_constant_value (expr);
return expr;
}
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 788b96de243..262ba5d309c 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1299,10 +1299,8 @@ build_noexcept_spec (tree expr, tsubst_flags_t complain)
if (TREE_CODE (expr) != DEFERRED_NOEXCEPT
&& !value_dependent_expression_p (expr))
{
- expr = instantiate_non_dependent_expr_sfinae (expr, complain);
- /* Don't let convert_like_real create more template codes. */
- processing_template_decl_sentinel s;
expr = build_converted_constant_bool_expr (expr, complain);
+ expr = instantiate_non_dependent_expr_sfinae (expr, complain);
expr = cxx_constant_value (expr);
}
if (TREE_CODE (expr) == INTEGER_CST)
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1c721b31176..49ee3920049 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7068,26 +7068,6 @@ convert_nontype_argument (tree type, tree expr,
tsubst_flags_t complain)
else if (INTEGRAL_OR_ENUMERATION_TYPE_P (type)
|| cxx_dialect >= cxx17)
{
- /* Calling build_converted_constant_expr might create a call to
- a conversion function with a value-dependent argument, which
- could invoke taking the address of a temporary representing
- the result of the conversion. */
- if (!same_type_ignoring_top_level_qualifiers_p (type, expr_type)
- && ((COMPOUND_LITERAL_P (expr)
- && CONSTRUCTOR_IS_DEPENDENT (expr)
- && MAYBE_CLASS_TYPE_P (expr_type)
- && TYPE_HAS_CONVERSION (expr_type))
- /* Similarly, converting e.g. an integer to a class
- involves a constructor call. convert_like would
- create a TARGET_EXPR, but in a template we can't
- use AGGR_INIT_EXPR, and the TARGET_EXPR would lead
- to a bogus error. */
- || (val_dep_p && MAYBE_CLASS_TYPE_P (type))))
- {
- expr = build1 (IMPLICIT_CONV_EXPR, type, expr);
- IMPLICIT_CONV_EXPR_NONTYPE_ARG (expr) = true;
- return expr;
- }
/* C++17: A template-argument for a non-type template-parameter shall
be a converted constant expression (8.20) of the type of the
template-parameter. */
@@ -7096,6 +7076,11 @@ convert_nontype_argument (tree type, tree expr,
tsubst_flags_t complain)
/* Make sure we return NULL_TREE only if we have really issued
an error, as described above. */
return (complain & tf_error) ? NULL_TREE : error_mark_node;
+ else if (TREE_CODE (expr) == IMPLICIT_CONV_EXPR)
+ {
+ IMPLICIT_CONV_EXPR_NONTYPE_ARG (expr) = true;
+ return expr;
+ }
expr = maybe_constant_value (expr, NULL_TREE,
/*manifestly_const_eval=*/true);
expr = convert_from_reference (expr);
diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index 48920894b3b..bff4ddbcf81 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -981,7 +981,11 @@ check_narrowing (tree type, tree init, tsubst_flags_t
complain,
return ok;
}
- init = maybe_constant_value (init);
+ /* Even non-dependent expressions can still have template
+ codes like CAST_EXPR, so use *_non_dependent_expr to cope. */
+ init = fold_non_dependent_expr (init, complain);
+ if (init == error_mark_node)
+ return ok;
/* If we were asked to only check constants, return early. */
if (const_only && !TREE_CONSTANT (init))
diff --git a/gcc/testsuite/g++.dg/cpp0x/conv-tmpl2.C
b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl2.C
new file mode 100644
index 00000000000..8a505769c3c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl2.C
@@ -0,0 +1,21 @@
+// PR c++/92031 - bogus taking address of rvalue error.
+// { dg-do compile { target c++11 } }
+
+struct x { const int& l; };
+
+void a(const x&) {}
+
+template<class E>
+void f() {
+ a(x { 0 });
+}
+
+void g() {
+ a(x { 0 });
+}
+
+void
+test ()
+{
+ f<int>();
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/conv-tmpl3.C
b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl3.C
new file mode 100644
index 00000000000..e2021aa13e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl3.C
@@ -0,0 +1,16 @@
+// PR c++/91465 - ICE with template codes in check_narrowing.
+// { dg-do compile { target c++11 } }
+
+enum class D { X };
+enum class S { Z };
+
+D foo(S) { return D{}; }
+D foo(double) { return D{}; }
+
+template <typename>
+struct Bar {
+ D baz(S s)
+ {
+ return D{foo(s)};
+ }
+};
diff --git a/gcc/testsuite/g++.dg/cpp0x/conv-tmpl4.C
b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl4.C
new file mode 100644
index 00000000000..966a2e1ac9e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl4.C
@@ -0,0 +1,33 @@
+// PR c++/93870 - wrong error when converting template non-type arg.
+// { dg-do compile { target c++11 } }
+
+template <typename ENUM> struct EnumWrapper
+{
+ ENUM value;
+
+ constexpr operator ENUM() const
+ {
+ return value;
+ }
+};
+
+enum E : int { V };
+
+constexpr EnumWrapper<E> operator ~(E a)
+{
+ return {E(~int(a))};
+}
+
+template <E X> struct R
+{
+ static void Func();
+};
+
+template <E X> struct S : R<~X>
+{
+};
+
+void Test()
+{
+ S<E::V>::Func();
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/conv-tmpl5.C
b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl5.C
new file mode 100644
index 00000000000..c83e6d83ed9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl5.C
@@ -0,0 +1,13 @@
+// PR c++/94068 - ICE with template codes in check_narrowing.
+// { dg-do compile { target c++11 } }
+
+enum class A { A1, A2 };
+A foo ();
+long foo (int);
+
+template <typename>
+void
+bar ()
+{
+ const auto c{foo ()};
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/conv-tmpl6.C
b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl6.C
new file mode 100644
index 00000000000..2df3a6cc129
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/conv-tmpl6.C
@@ -0,0 +1,16 @@
+// { dg-do compile { target c++11 } }
+
+struct A
+{
+ constexpr A(int) { }
+ constexpr operator int() const { return 1; };
+};
+
+template <class T, int N>
+struct B
+{
+ static constexpr A a = A(N);
+ int ar[a];
+};
+
+B<int, 10> b;
diff --git a/gcc/testsuite/g++.dg/cpp1z/conv-tmpl1.C
b/gcc/testsuite/g++.dg/cpp1z/conv-tmpl1.C
new file mode 100644
index 00000000000..5b1205349d0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/conv-tmpl1.C
@@ -0,0 +1,10 @@
+// PR c++/91465 - ICE with template codes in check_narrowing.
+// { dg-do compile { target c++17 } }
+
+enum class E { Z };
+
+template <typename F>
+void foo(F)
+{
+ E{char(0)};
+}
base-commit: 81fa6d7321dd9b645d86de4a8a6967c603f176e3
