On Sun, Feb 09, 2020 at 01:51:13PM +0100, Jason Merrill wrote:
> On 2/6/20 7:30 PM, Marek Polacek wrote:
> > In ed4f2c001a883b2456fc607a33f1c59f9c4ee65d I changed the call to
> > fold_non_dependent_expr in check_narrowing to maybe_constant_value.
> > That was the wrong thing to do as these tests show: check_narrowing
> > bails out for dependent expressions but we can still have template
> > codes like CAST_EXPR that don't have anything dependent in it so are
> > considered non-dependent. But cxx_eval_* don't grok template codes,
> > so we need to call fold_non_dependent_expr instead which knows what
> > to do with template codes. (I fully accept a "told you so".)
> >
> > I'm passing tf_none to it, otherwise we'd emit a bogus error for
> > constexpr-ex4.C: there INIT is "A::operator int(&a)" and while
> > instantiating this CALL_EXPR (in a template) we call finish_call_expr
> > and that sees a BASELINK and so emits a new dummy object for 'this',
> > and then we complain about the wrong number of arguments, because now
> > we basically have two 'this's. Which is exactly the problem I saw
> > recently in c++/92948.
>
> Yeah, the problem continues to be that build_converted_constant_expr is
> breaking the boundary between template and non-template codes:
> convert_like_real produces trees that aren't suitable for later
> substitution, so substituting them breaks. Perhaps if we're looking at a
> non-dependent constant expression in a template,
> build_converted_constant_expr should instantiate_non_dependent_expr, pass
> the result to convert_like, and then if successful throw away the result in
> favor of an IMPLICIT_CONV_EXPR.
That seems to work (if I adjust two spots to handle an I_C_E). So something
like this? I don't like that we create an I_C_E in convert_nontype_argument
and in build_converted_constant_expr too, but both are important. And we
should not forget to set IMPLICIT_CONV_EXPR_NONTYPE_ARG.
Not the does not fix PR92031, another "taking address of rvalue" because
substitution creates an & around a TARGET_EXPR. I suspect creating an I_C_E
somewhere will be the fix for that too.
-- >8 --
In ed4f2c001a883b2456fc607a33f1c59f9c4ee65d I changed the call to
fold_non_dependent_expr in check_narrowing to maybe_constant_value.
That was the wrong thing to do as these tests show: check_narrowing
bails out for dependent expressions but we can still have template
codes like CAST_EXPR that don't have anything dependent in it so are
considered non-dependent. But cxx_eval_* don't grok template codes,
so we need to call fold_non_dependent_expr instead which knows what
to do with template codes. (I fully accept a "told you so".)
This patch also includes further tweaks so as to avoid a bogus error for
constexpr-ex4.C: there INIT is "A::operator int(&a)" and while
instantiating this CALL_EXPR (in a template) we call finish_call_expr
and that sees a BASELINK and so emits a new dummy object for 'this', and
then we would complain about the wrong number of arguments, because of
the two 'this's. Which is exactly the problem as in c++/92948.
So create an IMPLICIT_CONV_EXPR for a non-dependent expression in
a template in build_converted_constant_expr_internal, and adjust
some spots to handle that.
PR c++/91465 - ICE with template codes in check_narrowing.
* call.c (build_converted_constant_expr_internal): Use an
IMPLICIT_CONV_EXPR for a non-dependent expression in a template.
* decl.c (compute_array_index_type_loc): Use fold_non_dependent_expr
instead of maybe_constant_value.
* pt.c (convert_nontype_argument): Don't pass IMPLICIT_CONV_EXPRs
to maybe_constant_value.
* typeck2.c (check_narrowing): Use fold_non_dependent_expr
instead of maybe_constant_value.
* g++.dg/cpp0x/pr91465.C: New test.
* g++.dg/cpp1z/pr91465.C: New test.
---
gcc/cp/call.c | 11 +++++++++++
gcc/cp/decl.c | 5 ++---
gcc/cp/pt.c | 7 +++++++
gcc/cp/typeck2.c | 4 +++-
gcc/testsuite/g++.dg/cpp0x/pr91465.C | 16 ++++++++++++++++
gcc/testsuite/g++.dg/cpp1z/pr91465.C | 10 ++++++++++
6 files changed, 49 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/pr91465.C
create mode 100644 gcc/testsuite/g++.dg/cpp1z/pr91465.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 51621b7dd87..91f5259d957 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4366,6 +4366,17 @@ build_converted_constant_expr_internal (tree type, tree
expr,
&& processing_template_decl)
conv = next_conversion (conv);
+ /* convert_like produces trees that aren't suitable for
+ substitution, so use an IMPLICIT_CONV_EXPR. */
+ if (processing_template_decl
+ && is_nondependent_constant_expression (expr))
+ {
+ tree e = instantiate_non_dependent_expr (expr);
+ e = convert_like (conv, e, complain);
+ if (e != error_mark_node)
+ return build1 (IMPLICIT_CONV_EXPR, type, expr);
+ }
+
conv->check_narrowing = true;
conv->check_narrowing_const_only = true;
expr = convert_like (conv, expr, complain);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 31a556a0a1f..5eb91007e9e 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10281,9 +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);
if (!TREE_CONSTANT (size))
size = origsize;
}
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index c2d3a98b1c5..5d207da2f5b 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7099,6 +7099,13 @@ 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;
+ /* Don't pass any IMPLICIT_CONV_EXPRs to maybe_constant_value
+ because that can't handle it. */
+ 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..59998d38c04 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -981,7 +981,9 @@ check_narrowing (tree type, tree init, tsubst_flags_t
complain,
return ok;
}
- init = maybe_constant_value (init);
+ 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/pr91465.C
b/gcc/testsuite/g++.dg/cpp0x/pr91465.C
new file mode 100644
index 00000000000..e2021aa13e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr91465.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/cpp1z/pr91465.C
b/gcc/testsuite/g++.dg/cpp1z/pr91465.C
new file mode 100644
index 00000000000..5b1205349d0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/pr91465.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: f348846e25573bc1f62f5a26317c331ad8dce041
--
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
