Re: [PATCH 3/3] lto-plugin: implement LDPT_GET_API_VERSION

["Martin Liška" <mliska@suse.cz>]

On 7/11/22 14:24, Rui Ueyama wrote:
> I updated my patch to support the proposed API:
> https://github.com/rui314/mold/commit/22bbfa9bba9beeaf40b76481d175939ee2c62ec8
> 
> Martin,
> 
> I think you want to apply this patch. Currently, your API always
> passes LAPI_V0 as the maximum API version.

Are you sure?

The function signature is:

(*ld_plugin_get_api_version) (const char *plugin_identifier,
                             const char *plugin_version,
                             enum linker_api_version minimal_api_supported,
                             enum linker_api_version maximal_api_supported,
...

Which means the plug-in always set minimal as LAPI_V0 and maximal
LAPI_V0/V1. That seems correct to me.

Martin


> 
> diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c
> index e9afd2fb76d..c97bda9de91 100644
> --- a/lto-plugin/lto-plugin.c
> +++ b/lto-plugin/lto-plugin.c
> @@ -1441,15 +1441,15 @@ negotiate_api_version (void)
>    const char *linker_version;
> 
>    enum linker_api_version supported_api = LAPI_V0;
>  #if HAVE_PTHREAD_LOCKING
>    supported_api = LAPI_V1;
>  #endif
> 
> -  api_version = get_api_version ("GCC", BASE_VERSION, LAPI_V0,
> +  api_version = get_api_version ("GCC", BASE_VERSION, LAPI_V1,
>                                  supported_api, &linker_identifier,
> &linker_version);
>    if (api_version > supported_api)
>      {
>        fprintf (stderr, "requested an unsupported API version (%d)\n",
> api_version);
>        abort ();
>      }
> 
> On Mon, Jul 11, 2022 at 6:51 PM Martin Liška <mliska@suse.cz> wrote:
>>
>> On 7/11/22 11:55, Richard Biener wrote:
>>> On Mon, Jul 11, 2022 at 11:16 AM Alexander Monakov <amonakov@ispras.ru> wrote:
>>>>
>>>> On Mon, 11 Jul 2022, Rui Ueyama wrote:
>>>>
>>>>>> but ignoring min_api_supported is wrong, and assuming max_api_supported > 0
>>>>>> is also wrong. It really should check how given [min; max] range intersects
>>>>>> with its own range of supported versions.
>>>>>
>>>>> Currently only one version is defined which is LAPI_V1. I don't think
>>>>> LAPI_UNSPECIFIED is a version number; rather, it's an unspecified
>>>>> value. No ordering should be defined between a defined value and an
>>>>> unspecified value. If LAPI_UNSPECIFIED < LAPI_V1, it should be renamed
>>>>> LAPI_V0.
>>>>
>>>> You still cannot rely on API guarantees of LAPI_V1 when the plugin does not
>>>> advertise it (thread safety of claim_file in this particular case).
>>>
>>
>> Hi.
>>
>> All right, I think we should rename LAPI_UNSPECIFIED to LAPI_V0 in order
>> to support minimal_api_supported == LAPI_V0.
>>
>>> So with LAPI_UNSPECIFIED all the plugin gets is the linker name and version.
>>> Clarifying the documentation on LAPI_UNSPECIFIED might be nice, also
>>> what the expectation is on the linker when the plugin returns
>>> LAPI_UNSPECIFIED when it speficied minimal_api_supported == V1.
>>
>> I've clarified that linker should return a value that is in range
>> [minimal_api_supported, maximal_api_supported] and added an abort
>> if it's not the case.
>>
>> Having that, mold should respect if maximal_api_supported == LAPI_V0 is returned
>> by a plug-in (happens now as we miss locking for some targets).
>>
>> Martin
>>
>>> "minimal_api_supported == LAPI_UNSPECIFIED" does not make much
>>> sense if using Ruis reading of this value?
>>>
>>>> And you still should check the intersection of supported API ranges
>>>> and give a sane diagnostic when min_api_supported advertised by the plugin
>>>> exceeds LAPI_V1 (though, granted, the plugin could error out as well in this
>>>> case).
>>>>
>>>> Alexander