Re: [PATCH] suppression: Add "has_strict_flexible_array_data_member_conversion" property

[Dodji Seketeli <dodji@redhat.com>]

Hello,

"quic_johmoo at quicinc dot com" <sourceware-bugzilla@sourceware.org> a
écrit:

> https://sourceware.org/bugzilla/show_bug.cgi?id=31017
>
> --- Comment #6 from John Moon <quic_johmoo at quicinc dot com> ---
> Thanks for pushing it across the finish line! I just tested it and seems to be
> working correctly for me. 👍

Thanks, so I have applied the patch below to the master branch of the
git repository.  I should be available in the upcoming libabigail 2.5
release.

Meanwhile, I am updating the libabigail 2.4 packages in the Fedora Linux
distribution to make them carry this patch as well as another one that
fixes https://sourceware.org/bugzilla/show_bug.cgi?id=31045.

That way, Fedora users should soon (before libabigail 2.5) be able to
use check-uapi.sh with all the relevant changes in libabigail.

Note that the patches I am pushing to the Fedora distribution are all in
the libabigail-2.4-branch of the git repository that can be browsed at
https://sourceware.org/git/?p=libabigail.git;a=shortlog;h=refs/heads/libabigail-2.4-branch.
Other distributions are of course encouraged to update their libabigail
2.4 package to add the patches that are in that branch.

Dodji Seketeli <dodji@redhat.com> a écrit:

[...]

> From fe1dbee8e8c5211c910d9b72fccd1230600be4ab Mon Sep 17 00:00:00 2001
> From: Dodji Seketeli <dodji@redhat.com>
> Date: Fri, 3 Nov 2023 17:47:57 -0700
> Subject: [PATCH] suppression: Add "has_strict_flexible_array_data_member_conversion" property
>
> In the past, it was common to have a "fake flex array" at the end of a
> structure. Like this:
>
> Nowadays, with improved compiler support, it's more common to use a real
> flex array. As this is a common change which changes ABI representation
> in a compatible way, we should have a suppression for it.
>
> For example, if you have a change like this:
>
> struct foo {
>     int x;
>     int flex[1];
> };
>
> ...
>
> struct foo {
>     int x;
>     int flex[];
> };
>
> abidiff reports:
>
>   [C] 'struct foo' changed:
>     type size changed from 64 to 32 (in bits)
>     1 data member change:
>       type of 'int flex[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'
>
> With a new has_strict_flexible_array_data_member_conversion property,
> users can specify a suppression which stops abidiff from emitting
> this diff for any "fake" flex arrays being converted to real ones:
>
> [suppress_type]
>   type_kind = struct
>   has_size_change = true
>   has_strict_flexible_array_data_member_conversion = true
>
> 	* include/abg-comp-filter.h (has_strict_fam_conversion): Declare
> 	new functions.
> 	* include/abg-fwd.h
> 	(ir::has_fake_flexible_array_data_member): Declare new accessor
> 	functions.
> 	* include/abg-suppression.h
> 	(type_suppression::{,set_}has_strict_fam_conversion): Declare new
> 	accessor functions.
> 	* src/abg-comp-filter.cc (has_strict_fam_conversion): Define new
> 	functions.
> 	* src/abg-ir.cc
> 	(ir::has_fake_flexible_array_data_member): Define new accessor
> 	functions.
> 	* src/abg-suppression-priv.h
> 	(type_suppression::priv::has_strict_fam_conv_): Define new
> 	data member.
> 	* src/abg-suppression.cc
> 	(type_suppression::{,set_}has_strict_fam_conversion): Define new
> 	accessor functions.
> 	(type_suppression::suppresses_diff): For a type suppression to
> 	match a fake flex array conversion, either the size of the type
> 	hasn't change or has_size_change must be true and then the type
> 	must change from a fake flex array to a real flex array.
> 	(read_type_suppression): Parse the new
> 	'has_strict_flexible_array_data_member_conversion' property to
> 	set the type_suppression::set_has_strict_fam_conversion property.
> 	* doc/manuals/libabigail-concepts.rst: Add an entry for the new
> 	'has_strict_flexible_array_data_member_conversion' property.
> 	* tests/data/test-diff-suppr/test-has-strict-flexible-array-data-member-conversion-{1,2}.suppr:
> 	Add new test suppression files.
> 	* tests/data/test-diff-suppr/test-has-strict-flexible-array-data-member-conversion-report-{1,2}.txt:
> 	Add new test reference output files.
> 	* tests/data/test-diff-suppr/test-has-strict-flexible-array-data-member-conversion-v{0,1}.c:
> 	Add source code for new binary test input files.
> 	* tests/data/test-diff-suppr/test-has-strict-flexible-array-data-member-conversion-v{0,1}.o:
> 	Add new binary test input files.
> 	* tests/data/Makefile.am: Add the new test files to the source
> 	distribution.
> 	* tests/test-diff-suppr.cc (in_out_specs): Add the new test input
> 	files to this test harness.
>
> Signed-off-by: Dodji Seketeli <dodji@redhat.com>
> Signed-off-by: John Moon <quic_johmoo@quicinc.com>

[...]

Cheers,

-- 
		Dodji