Re: [PATCH] c++: abi_tag attribute on templates [PR109715]

[Jason Merrill <jason@redhat.com>]

On 12/14/23 16:08, Patrick Palka wrote:
> On Thu, 14 Dec 2023, Jason Merrill wrote:
> 
>> On 12/14/23 14:17, Patrick Palka wrote:
>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
>>> trunk?  Do we want to condition this on abi_check (19)?
>>
>> I think we do, sadly.
> 
> Sounds good, like so?  Bootstrap and regtest in progress.
> 
> -- >8 --
> 
> Subject: [PATCH] c++: abi_tag attribute on templates [PR109715]
> 
> As with other declaration attributes, we need to look through
> TEMPLATE_DECL when looking up the abi_tag attribute.
> 
> 	PR c++/109715
> 
> gcc/cp/ChangeLog:
> 
> 	* mangle.cc (get_abi_tags): Look through TEMPLATE_DECL.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/abi/abi-tag25.C: New test.
> 	* g++.dg/abi/abi-tag25a.C: New test.
> ---
>   gcc/cp/mangle.cc                      |  6 ++++++
>   gcc/testsuite/g++.dg/abi/abi-tag25.C  | 17 +++++++++++++++++
>   gcc/testsuite/g++.dg/abi/abi-tag25a.C | 11 +++++++++++
>   3 files changed, 34 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/abi/abi-tag25.C
>   create mode 100644 gcc/testsuite/g++.dg/abi/abi-tag25a.C
> 
> diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
> index 0684f0e6038..e3383df1836 100644
> --- a/gcc/cp/mangle.cc
> +++ b/gcc/cp/mangle.cc
> @@ -530,6 +530,12 @@ get_abi_tags (tree t)
>     if (DECL_P (t) && DECL_DECLARES_TYPE_P (t))
>       t = TREE_TYPE (t);
>   
> +  if (TREE_CODE (t) == TEMPLATE_DECL
> +      && DECL_TEMPLATE_RESULT (t)
> +      /* We used to ignore abi_tag on function and variable templates.  */
> +      && abi_check (19))
> +    t = DECL_TEMPLATE_RESULT (t);

Generally I try to call abi_check only when we know that there's 
something that will change the mangling, so here only if the template 
has ABI tags.  I suppose the only downside is a second mangling that 
produces the same name and gets ignored in mangle_decl so we don't need 
to be too strict about it, but it shouldn't be too hard to do that here?

Jason