[Bug default/31017] New: Flex array conversion suppression

["quic_johmoo at quicinc dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31017

            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];
}; 

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/c6f2e6b6eaaf883df482cb94f302acad9b80a2a4

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

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

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' 

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

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

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