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From: "gprocida+abigail at google dot com" <sourceware-bugzilla@sourceware.org>
To: libabigail@sourceware.org
Subject: [Bug default/27569] New: abidiff misses a function parameter addition
Date: Fri, 12 Mar 2021 15:21:37 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27569

            Bug ID: 27569
           Summary: abidiff misses a function parameter addition
           Product: libabigail
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: gprocida+abigail at google dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

Created attachment 13304
  --> https://sourceware.org/bugzilla/attachment.cgi?id=3D13304&action=3Ded=
it
two XML files to compare

Hi Dodji.

I'm attaching two reduced (manually edited, pruned) ABIs. Alas, they are st=
ill
quite large. I've tried and failed to reproduce the issue with a small test
case.

abidiff reports nothing, but should report this:

  [C] 'function void device_add_disk(gendisk*)' at genhd.h:420:1 has some
indirect sub-type changes:
    parameter 2 of type 'int' was added

Note that adding --redundant makes no difference.

Changing the type of the first argument in common to int made the problem go
away.

I believe I've narrowed the problem down to diff filtering.

Looking at apply_filters_and_compute_diff_stats, is_filtered_out for the si=
ngle
function diff initially returns true, but this changes to false after
filtering.

The category of the diff changes from NO_CHANGE_CATEGORY before the filteri=
ng
and to HARMLESS_UNION_CHANGE_CATEGORY|FN_RETURN_TYPE_CV_CHANGE_CATEGORY
afterwards. I believe these values come from deep within inconsequential
changes to the first argument's type. Exactly one filter is applied:
harmless_harmful_filter.

My best guess is that there is a hole in the category classification for
"incompatible function type/decl changes", though it seems unlikely that th=
is
wasn't noticed before now.

Regards,
Giuliano.

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