Re: [PATCH dwarves 2/4] btf_encoder: Refactor elf_functions__new() with struct btf_encoder as argument

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 1/13/26 5:13 AM, Alan Maguire wrote:
> From: Yonghong Song <yonghong.song@linux.dev>
> 
> For elf_functions__new(), replace original argument 'Elf *elf' with
> 'struct btf_encoder *encoder' for future use.
> 
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>  btf_encoder.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/btf_encoder.c b/btf_encoder.c
> index 2c3cef9..5bc61cb 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -187,11 +187,13 @@ static inline void elf_functions__delete(struct elf_functions *funcs)
>  
>  static int elf_functions__collect(struct elf_functions *functions);
>  
> -struct elf_functions *elf_functions__new(Elf *elf)
> +struct elf_functions *elf_functions__new(struct btf_encoder *encoder)

Hi Alan, Yonghong,

I assume "future use" refers to this patch:
https://lore.kernel.org/dwarves/20251130040350.2636774-1-yonghong.song@linux.dev/

Do I understand correctly that you're passing btf_encoder here in
order to detect that the `encoder->dotted_true_signature` feature flag
is set? If so, I think this is a bit of an overkill.

How about just store the flag in struct elf_functions, pass it to the
elf_functions__new() directly and set it there:

	funcs->elf = elf;
	funcs->dotted_true_signature = dotted_true_signature; // <--
	err = elf_functions__collect(funcs);
	if (err < 0)
		goto out_delete;

And even then, it doesn't feel right to me that the contents of the
*ELF* functions table changes based on a feature flag. But we are
discarding the suffixes currently, so I understand why this was done.

Taking a step back, I remember Yonghong mentioned some pushback both
from LLVM and DWARF side regarding the introduction of true signatures
to DWARF data. Is there a feasible path forward landing all that?

I haven't followed this work in detail, so apologies if I missed
anything. Just want to have a high-level understanding of the
situation.

Thank you!


>  {
>  	struct elf_functions *funcs;
> +	Elf *elf;
>  	int err;
>  
> +	elf = encoder->cu->elf;
>  	funcs = calloc(1, sizeof(*funcs));
>  	if (!funcs) {
>  		err = -ENOMEM;
> @@ -1552,7 +1554,7 @@ static struct elf_functions *btf_encoder__elf_functions(struct btf_encoder *enco
>  
>  	funcs = elf_functions__find(encoder->cu->elf, &encoder->elf_functions_list);
>  	if (!funcs) {
> -		funcs = elf_functions__new(encoder->cu->elf);
> +		funcs = elf_functions__new(encoder);
>  		if (funcs)
>  			list_add(&funcs->node, &encoder->elf_functions_list);
>  	}