On Tue, Mar 17, 2020 at 04:05:31PM -0400, Jason Merrill wrote:
> On 3/16/20 10:01 PM, Marek Polacek wrote:
> > On Mon, Mar 16, 2020 at 05:12:15PM -0400, Jason Merrill wrote:
> > > On 3/16/20 10:57 AM, Marek Polacek wrote:
> > > > Now that convert_like creates an IMPLICIT_CONV_EXPR when it converts
> > > > something that involves a class in a template, we must be prepared to
> > > > handle it. In this test, we have a class S and we're converting it
> > > > to long int& using a user-defined conversion since we're performing
> > > > -- on it. So cp_build_unary_op/POSTDECREMENT_EXPR calls
> > > > build_expr_type_conversion which gets the IMPLICIT_CONV_EXPR. Before
> > > > the convert_like change it got *S::operator long int &(&b) whose type
> > > > is long int but now it gets IMPLICIT_CONV_EXPR<long int&>(b) whose type
> > > > is a reference type.
> > >
> > > So you need to make sure that your IMPLICIT_CONV_EXPR gets
> > > convert_from_reference'd at some point.
> >
> > Perhaps like the following?
> >
> > Bootstrapped/regtested on x86_64-linux, built Boost/cmcstl2.
> >
> > -- >8 --
> > Now that convert_like creates an IMPLICIT_CONV_EXPR when it converts
> > something that involves a class in a template, we must be prepared to
> > handle it. In this test, we have a class S and we're converting it
> > to long int& using a user-defined conversion since we're performing
> > -- on it. So cp_build_unary_op/POSTDECREMENT_EXPR calls
> > build_expr_type_conversion which gets the IMPLICIT_CONV_EXPR. Before
> > the convert_like change it got *S::operator long int &(&b) whose type
> > is long int but now it gets IMPLICIT_CONV_EXPR<long int&>(b) whose type
> > is a reference type. But the !MAYBE_CLASS_TYPE_P switch doesn't handle
> > reference types and so we complain.
> >
> > Fixed by calling convert_from_reference on the result of convert_like.
> >
> > PR c++/94190 - wrong no post-decrement operator error in template.
> > * call.c (build_new_op_1): Use convert_from_reference on the result
> > of convert_like.
>
> The result of convert_like should already be dereferenced in this case. I
> think convert_like should only return a bare reference for ck_ref_bind,
> where we're explicitly requesting one.
I tried to adjust all the appropriate return ...; in convert_like to return
convert_from_reference (...); and then remove unnecessary calls to
convert_from_reference after a call to convert_like elsewhere in the codebase,
but that fails very badly.
But it seems we can use convert_from_reference in convert_like when returning
the new IMPLICIT_CONV_EXPR, like this:
Bootstrapped/regtested on x86_64-linux, ok for trunk?
-- >8 --
Now that convert_like creates an IMPLICIT_CONV_EXPR when it converts
something that involves a class in a template, we must be prepared to
handle it. In this test, we have a class S and we're converting it
to long int& using a user-defined conversion since we're performing
-- on it. So cp_build_unary_op/POSTDECREMENT_EXPR calls
build_expr_type_conversion which gets the IMPLICIT_CONV_EXPR. Before
the convert_like change it got *S::operator long int &(&b) whose type
is long int but now it gets IMPLICIT_CONV_EXPR<long int&>(b) whose type
is a reference type. But the !MAYBE_CLASS_TYPE_P switch doesn't handle
reference types and so we complain.
Fixed by calling convert_from_reference on the result of convert_like.
PR c++/94190 - wrong no post-decrement operator error in template.
* call.c (convert_like_real): Use convert_from_reference on the result.
* g++.dg/conversion/op7.C: New test.
---
gcc/cp/call.c | 5 ++++-
gcc/testsuite/g++.dg/conversion/op7.C | 22 ++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/conversion/op7.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 65a3ea35dee..bae4b2c0f52 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7389,7 +7389,10 @@ convert_like_real (conversion *convs, tree expr, tree
fn, int argnum,
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);
+ {
+ expr = build1 (IMPLICIT_CONV_EXPR, totype, expr);
+ return convs->kind == ck_ref_bind ? expr : convert_from_reference (expr);
+ }
switch (convs->kind)
{
diff --git a/gcc/testsuite/g++.dg/conversion/op7.C
b/gcc/testsuite/g++.dg/conversion/op7.C
new file mode 100644
index 00000000000..c6401d109b4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/op7.C
@@ -0,0 +1,22 @@
+// PR c++/94190 - wrong no post-decrement operator error in template.
+
+struct S { operator long & (); } b;
+
+template<int> void
+foo ()
+{
+ b--;
+ ++b;
+ --b;
+ b++;
+ !b;
+ ~b;
+ +b;
+ -b;
+}
+
+void
+bar ()
+{
+ foo<0> ();
+}
base-commit: a3586eeb88414e77c7cccb69362b8d04562536b6
--
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
