On Thu, Feb 20, 2020 at 12:28:42AM +0000, Jason Merrill wrote:
> On 2/19/20 7:30 PM, Marek Polacek wrote:
> > On Fri, Feb 14, 2020 at 09:12:58AM +0100, Jason Merrill wrote:
> > > On 2/13/20 8:56 PM, Marek Polacek wrote:
> > > > My P0388R4 patch changed build_array_conv to create an identity
> > > > conversion at the start of the conversion chain.
> > >
> > > Hmm, an identity conversion of {} suggests that it has a type, which it
> > > doesn't in the language. I'm not strongly against it, but what was the
> > > reason for this change?
> >
> > There are two reasons:
> > 1) without it we couldn't get to the original expression at the start
> > of the conversion chain (saved in .u.expr), this is needed in compare_ics:
> > 10660 tree n1 = nelts_initialized_by_list_init (t1);
> > 10661 tree n2 = nelts_initialized_by_list_init (t2);
> > and nelts_initialized_by_list_init uses conv_get_original_expr for
> > arrays that have no dimensions.
>
> Ah, ck_aggr and ck_list probably should have used u.expr like ck_identity
> and ck_ambig....
>
> > 2) struct conversion says
> > /* An implicit conversion sequence, in the sense of [over.best.ics].
> > The first conversion to be performed is at the end of the chain.
> > That conversion is always a cr_identity conversion. */
> > and we were breaking that promise.
>
> ...or, if we're going to enforce this, ck_ambig will need to change as well.
>
> And build_aggr_conv and build_complex_conv will need adjusting (one way or
> another).
Changed my mind :-). Turned out using u.expr for ck_aggr is a much smaller
change. Moreover, that struct conversion talks about cr_identity, a rank,
not ck_identity.
ck_list uses u.list, so I'm not changing that.
-- >8 --
My P0388R4 patch changed build_array_conv to create an identity
conversion at the start of the conversion chain and now we crash
in convert_like_real:
7457 case ck_identity:
7458 if (BRACE_ENCLOSED_INITIALIZER_P (expr))
7459 {
7460 int nelts = CONSTRUCTOR_NELTS (expr);
7461 if (nelts == 0)
7462 expr = build_value_init (totype, complain);
7463 else if (nelts == 1)
7464 expr = CONSTRUCTOR_ELT (expr, 0)->value;
7465 else
7466 gcc_unreachable (); // HERE
7467 }
in a test like this
int f (int const (&)[2])
{ return f({1, "M"}); }
Instead of creating a ck_identity at the start of the conversion chain,
so that conv_get_original_expr can be used with a ck_aggr, let's set
u.expr for a ck_aggr, and adjust next_conversion not to try to see
what's next in the chain if it gets a ck_aggr.
Bootstrapped/regtested on x86_64-linux, built cmcstl2 and Boost, ok for
trunk?
2020-02-21 Marek Polacek <pola...@redhat.com>
PR c++/93712 - ICE with ill-formed array list-initialization.
* call.c (next_conversion): Return NULL for ck_aggr.
(build_aggr_conv): Set u.expr instead of u.next.
(build_array_conv): Likewise.
(build_complex_conv): Likewise.
(conv_get_original_expr): Handle ck_aggr.
* g++.dg/cpp0x/initlist-array11.C: New test.
---
gcc/cp/call.c | 17 +++++++++--------
gcc/testsuite/g++.dg/cpp0x/initlist-array11.C | 10 ++++++++++
2 files changed, 19 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/initlist-array11.C
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index f47f96bf1c2..84230b9ecb8 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -117,13 +117,13 @@ struct conversion {
/* The next conversion in the chain. Since the conversions are
arranged from outermost to innermost, the NEXT conversion will
actually be performed before this conversion. This variant is
- used only when KIND is neither ck_identity, ck_ambig nor
+ used only when KIND is neither ck_identity, ck_aggr, ck_ambig nor
ck_list. Please use the next_conversion function instead
of using this field directly. */
conversion *next;
/* The expression at the beginning of the conversion chain. This
- variant is used only if KIND is ck_identity or ck_ambig. You can
- use conv_get_original_expr to get this expression. */
+ variant is used only if KIND is ck_identity, ck_aggr, or ck_ambig.
+ You can use conv_get_original_expr to get this expression. */
tree expr;
/* The array of conversions for an initializer_list, so this
variant is used only when KIN D is ck_list. */
@@ -861,7 +861,8 @@ next_conversion (conversion *conv)
if (conv == NULL
|| conv->kind == ck_identity
|| conv->kind == ck_ambig
- || conv->kind == ck_list)
+ || conv->kind == ck_list
+ || conv->kind == ck_aggr)
return NULL;
return conv->u.next;
}
@@ -1030,7 +1031,7 @@ build_aggr_conv (tree type, tree ctor, int flags,
tsubst_flags_t complain)
c->rank = cr_exact;
c->user_conv_p = true;
c->check_narrowing = true;
- c->u.next = NULL;
+ c->u.expr = ctor;
return c;
}
@@ -1083,7 +1084,7 @@ build_array_conv (tree type, tree ctor, int flags,
tsubst_flags_t complain)
c->rank = rank;
c->user_conv_p = user;
c->bad_p = bad;
- c->u.next = build_identity_conv (TREE_TYPE (ctor), ctor);
+ c->u.expr = ctor;
return c;
}
@@ -1129,7 +1130,7 @@ build_complex_conv (tree type, tree ctor, int flags,
c->rank = rank;
c->user_conv_p = user;
c->bad_p = bad;
- c->u.next = NULL;
+ c->u.expr = ctor;
return c;
}
@@ -10498,7 +10499,7 @@ static tree
conv_get_original_expr (conversion *c)
{
for (; c; c = next_conversion (c))
- if (c->kind == ck_identity || c->kind == ck_ambig)
+ if (c->kind == ck_identity || c->kind == ck_ambig || c->kind == ck_aggr)
return c->u.expr;
return NULL_TREE;
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-array11.C
b/gcc/testsuite/g++.dg/cpp0x/initlist-array11.C
new file mode 100644
index 00000000000..d3e58dea129
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-array11.C
@@ -0,0 +1,10 @@
+// PR c++/93712 - ICE with ill-formed array list-initialization.
+// { dg-do compile { target c++11 } }
+
+int f (const int (&)[2]);
+
+int g ()
+{
+ const int (&r)[2] = {1, "foo"}; // { dg-error "conversion" }
+ return f({1, "foo"}); // { dg-error "conversion" }
+}
base-commit: 8d1780b56d0cb1d50115d4e925e81cd8b9cb2923
--
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
