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

[Rui Ueyama <rui314@gmail.com>]

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.

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