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From: "quic_johmoo at quicinc dot com" <sourceware-bugzilla@sourceware.org>
To: libabigail@sourceware.org
Subject: [Bug default/31017] New: Flex array conversion suppression
Date: Tue, 31 Oct 2023 18:34:13 +0000
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X-Bugzilla-Product: libabigail
X-Bugzilla-Component: default
X-Bugzilla-Version: unspecified
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X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: quic_johmoo at quicinc dot com
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: dodji at redhat dot com
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31017

            Bug ID: 31017
           Summary: Flex array conversion suppression
           Product: libabigail
           Version: unspecified
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: quic_johmoo at quicinc dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

In the past, it was common in Linux kernel code to have a "fake flex array"=
 at
the end of a structure. Like this:

struct foo {
         int x;
         int y;
         int end[1];
};=20

In recent years, with improved compiler support, real flex arrays have been
preferred. It's common to see patches like this:
https://github.com/torvalds/linux/commit/c6f2e6b6eaaf883df482cb94f302acad9b=
80a2a4

Basically, this takes the struct above, and changes it to:

struct foo {
         int x;
         int y;
         int end[];
};=20

abidiff flags this change with:

   [C] 'struct foo' changed:
     type size changed from 96 to 64 (in bits)
     1 data member change:
       type of 'int end[1]' changed:
         type name changed from 'int[1]' to 'int[]'
         array type size changed from 32 to 'unknown'
         array type subrange 1 changed length from 1 to 'unknown'=20

It would be good to have a suppression to filter out this kind of change. F=
or
example:

     [suppress_type]
       type_kind =3D struct
       has_size_change =3D true
       has_strict_flexible_array_data_member_conversion =3D true

--=20
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