c++: fix ICE in joust_maybe_elide_copy [PR106675]
Checks
Commit Message
joust_maybe_elide_copy checks that the last conversion in the ICS for
the first argument is ck_ref_bind, which is reasonable, because we've
checked that we're dealing with a copy/move constructor. But it can
also happen that we couldn't figure out which conversion function is
better to convert the argument, as in this testcase: joust couldn't
decide if we should go with
operator foo &()
or
operator foo const &()
so we get a ck_ambig, which then upsets joust_maybe_elide_copy. Since
a ck_ambig can validly occur, I think we should just return early, as
in the patch below.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/12?
PR c++/106675
gcc/cp/ChangeLog:
* call.cc (joust_maybe_elide_copy): Return false for ck_ambig.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/overload-conv-5.C: New test.
---
gcc/cp/call.cc | 2 ++
gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C | 21 ++++++++++++++++++++
2 files changed, 23 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C
base-commit: 72ae1e5635648bd3f6a5760ca46d531ad1f2c6b1
Comments
On 2/13/23 09:06, Marek Polacek wrote:
> joust_maybe_elide_copy checks that the last conversion in the ICS for
> the first argument is ck_ref_bind, which is reasonable, because we've
> checked that we're dealing with a copy/move constructor. But it can
> also happen that we couldn't figure out which conversion function is
> better to convert the argument, as in this testcase: joust couldn't
> decide if we should go with
>
> operator foo &()
>
> or
>
> operator foo const &()
>
> so we get a ck_ambig, which then upsets joust_maybe_elide_copy. Since
> a ck_ambig can validly occur, I think we should just return early, as
> in the patch below.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/12?
OK.
> PR c++/106675
>
> gcc/cp/ChangeLog:
>
> * call.cc (joust_maybe_elide_copy): Return false for ck_ambig.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/overload-conv-5.C: New test.
> ---
> gcc/cp/call.cc | 2 ++
> gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C | 21 ++++++++++++++++++++
> 2 files changed, 23 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C
>
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index a349d8e79db..048b2b052f8 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -12542,6 +12542,8 @@ joust_maybe_elide_copy (z_candidate *&cand)
> if (!DECL_COPY_CONSTRUCTOR_P (fn) && !DECL_MOVE_CONSTRUCTOR_P (fn))
> return false;
> conversion *conv = cand->convs[0];
> + if (conv->kind == ck_ambig)
> + return false;
> gcc_checking_assert (conv->kind == ck_ref_bind);
> conv = next_conversion (conv);
> if (conv->kind == ck_user && !TYPE_REF_P (conv->type))
> diff --git a/gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C b/gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C
> new file mode 100644
> index 00000000000..b1e7766e42b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/overload-conv-5.C
> @@ -0,0 +1,21 @@
> +// PR c++/106675
> +// { dg-do compile { target c++11 } }
> +
> +struct foo {
> + int n_;
> + foo(int n) : n_(n) {}
> +};
> +
> +struct bar {
> + int n_;
> +
> + operator foo() const {
> + return foo(n_);
> + }
> + operator foo &() { return *reinterpret_cast<foo *>(n_); }
> + operator foo const &() = delete;
> +
> + void crashgcc() {
> + foo tmp(*this); // { dg-error "ambiguous" }
> + }
> +};
>
> base-commit: 72ae1e5635648bd3f6a5760ca46d531ad1f2c6b1
@@ -12542,6 +12542,8 @@ joust_maybe_elide_copy (z_candidate *&cand)
if (!DECL_COPY_CONSTRUCTOR_P (fn) && !DECL_MOVE_CONSTRUCTOR_P (fn))
return false;
conversion *conv = cand->convs[0];
+ if (conv->kind == ck_ambig)
+ return false;
gcc_checking_assert (conv->kind == ck_ref_bind);
conv = next_conversion (conv);
if (conv->kind == ck_user && !TYPE_REF_P (conv->type))
new file mode 100644
@@ -0,0 +1,21 @@
+// PR c++/106675
+// { dg-do compile { target c++11 } }
+
+struct foo {
+ int n_;
+ foo(int n) : n_(n) {}
+};
+
+struct bar {
+ int n_;
+
+ operator foo() const {
+ return foo(n_);
+ }
+ operator foo &() { return *reinterpret_cast<foo *>(n_); }
+ operator foo const &() = delete;
+
+ void crashgcc() {
+ foo tmp(*this); // { dg-error "ambiguous" }
+ }
+};