On Sat Jan 17, 2026 at 5:00 PM CET, Simon Martin wrote:
> We currently ICE in decl_linkage for the following invalid input
> because we access the TYPE_MAIN_VARIANT of error_mark_node
>
> ===
> extern "C" {
> template <a> class b;
> struct {
> typedef b:
> ===
>
> This patch fixes this by returning no linkage for any TYPE_DECL with an
> erroneous type.
>
> PR c++/122391
>
> gcc/cp/ChangeLog:
>
> * tree.cc (decl_linkage): Return lk_none for TYPE_DECLs with
> erroneous type.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/parse/bitfield10.C: New test.
>
I forgot to say that I've succesfully bootstrapped and regtested this on
x86_64-pc-linux-gnu. OK for trunk?
> ---
> gcc/cp/tree.cc | 11 +++++++----
> gcc/testsuite/g++.dg/parse/bitfield10.C | 9 +++++++++
> 2 files changed, 16 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/parse/bitfield10.C
>
> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> index a57eefaf11f3..030af4d219d1 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -6440,10 +6440,13 @@ decl_linkage (tree decl)
> {
> /* But this could be a typedef name for linkage purposes, in which
> case we're interested in the linkage of the main decl. */
> - if (decl == TYPE_NAME (TYPE_MAIN_VARIANT (TREE_TYPE (decl)))
> - /* Likewise for the injected-class-name. */
> - || DECL_SELF_REFERENCE_P (decl))
> - decl = TYPE_MAIN_DECL (TREE_TYPE (decl));
> + tree type = TREE_TYPE (decl);
> + if (type == error_mark_node)
> + return lk_none;
> + else if (decl == TYPE_NAME (TYPE_MAIN_VARIANT (type))
> + /* Likewise for the injected-class-name. */
> + || DECL_SELF_REFERENCE_P (decl))
> + decl = TYPE_MAIN_DECL (type);
> else
> return lk_none;
> }
> diff --git a/gcc/testsuite/g++.dg/parse/bitfield10.C
> b/gcc/testsuite/g++.dg/parse/bitfield10.C
> new file mode 100644
> index 000000000000..c5ab75932e7c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/parse/bitfield10.C
> @@ -0,0 +1,9 @@
> +/* PR c++/122391 */
> +/* { dg-do "compile" } */
> +
> +extern "C" {
> + template <int> class b; /* { dg-error "with C linkage" } */
> + struct {
> + typedef b: /* { dg-error "at end of input" } */
> +
> +/* { dg-excess-errors "" } */
