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Dodji Seketeli 5eb4d7627a Bug 25661 - Support data member replacement by anonymous data member
We ought to detect when a data member is replaced by an anonymous data
member in a way that doesn't change the ABI in an incompatible way,
especially when that change is non equivocal.

For instance, consider this ABI-visible struct:

    struct S
    {
      int a;
    };

Now, consider that it's changed into:

    struct S
    {
      union
      {
	int a;
	char b;
      };
    };

Stricto sensu, the bit-layout of struct S doesn't change and so that
change isn't ABI-incompatible.

The current version of libabigail however flags that change as a
/potential/ issue and asks the user for further review.  It appears
that this class of changes is frequent enough to be annoying,
especially in semi-automatic ABI compliance checking setups where we
want the least possible "false positives".

This patch detects that kind of change patterns where a data member is
replaced by an anonymous data member in a benign way, in terms of ABI.

So now let's look at a more complicated example where an ABI-visible
type looks like:

struct S
{
  int a;
  int b;
  int c;
};

Now suppose that type was changed into:

struct S
{
  union
  {
    int tag[3];
    struct
    {
      int a;
      int b;
      int c;
    };
  };
};

The patch allows abidiff to recognise that kind of pattern, filter out
the detected change and report by default that the two binaries are
ABI compatible.

Here are the output that we'd get:

$ abidiff test-v0.o test-v1.o
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable

When asked to show the detailed of the filtered out changes, we get:

$ abidiff --harmless test-v0.o test-v1.o
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable

1 function with some indirect sub-type change:

  [C] 'function void foo(S*)' at test-v1.cc:18:1 has some indirect sub-type changes:
    parameter 1 of type 'S*' has sub-type changes:
      in pointed to type 'struct S' at test-v1.cc:1:1:
        type size hasn't changed
        data members 'S::a', 'S::b', 'S::c' were replaced by anonymous data member:
          'union {int tag[3]; struct {int a; int b; int c;};}'

And using the leaf-node reporter, that would give:

$ abidiff --leaf-changes-only --harmless test-v0.o test-v1.o
Leaf changes summary: 1 artifact changed
Changed leaf types summary: 1 leaf type changed
Removed/Changed/Added functions summary: 0 Removed, 0 Changed, 0 Added function
Removed/Changed/Added variables summary: 0 Removed, 0 Changed, 0 Added variable

'struct S at test-v0.cc:1:1' changed:
  type size hasn't changed
  data members 'S::a', 'S::b', 'S::c' were replaced by anonymous data member:
    'union {int tag[3]; struct {int a; int b; int c;};}'

	* include/abg-comp-filter.h (has_data_member_replaced_by_anon_dm):
	Declare new function.
	* include/abg-comparison.h (changed_var_sptr)
	(changed_var_sptrs_type): Declare new typedefs.
	(HARMLESS_DATA_MEMBER_CHANGE_CATEGORY): Add a new enumerator to
	the diff_category enum.
	(EVERYTHING_CATEGORY): In the diff_category, adjust this
	enumerator to OR the new HARMLESS_DATA_MEMBER_CHANGE_CATEGORY into
	it.
	(SUPPRESSED_CATEGORY, PRIVATE_TYPE_CATEGORY)
	(SIZE_OR_OFFSET_CHANGE_CATEGORY, VIRTUAL_MEMBER_CHANGE_CATEGORY)
	(CLASS_DECL_ONLY_DEF_CHANGE_CATEGORY)
	(FN_PARM_TYPE_TOP_CV_CHANGE_CATEGORY)
	(FN_RETURN_TYPE_CV_CHANGE_CATEGORY, VAR_TYPE_CV_CHANGE_CATEGORY)
	(VOID_PTR_TO_PTR_CHANGE_CATEGORY)
	(BENIGN_INFINITE_ARRAY_CHANGE_CATEGORY): Adjust the value of these
	enumerators of the diff_category enum.
	(class_or_union_diff::{data_members_replaced_by_adms,
	ordered_data_members_replaced_by_adms}): Declare new member
	functions.
	* include/abg-fwd.h (var_decl_wptr): Declare new typedef.
	(get_next_data_member, get_first_non_anonymous_data_member)
	(find_data_member_from_anonymous_data_member)
	(get_absolute_data_member_offset): Declare new functions.
	* include/abg-ir.h (struct anonymous_dm_hash): Declare new type.
	(anonymous_data_member_sptr_set_type): Declare new typedef.
	(class decl_base): Befriend class class_or_union.
	(class dm_context_rel): Pimpl-ify this class.
	(dm_context_rel::{g,s}et_anonymous_data_member_types): Declare new
	member functions.
	(var_decl::get_anon_dm_reliable_name): Declare new member
	function.
	(class var_decl): Make get_absolute_data_member_offset,
	get_absolute_data_member_offset be friends of this.
	(class_or_union::maybe_fixup_members_of_anon_data_member): Declare
	new protected member function.
	* src/abg-comp-filter.cc (has_data_member_replaced_by_anon_dm):
	Define new function.
	(categorize_harmless_diff_node): Use the above.
	* src/abg-comparison-priv.h
	(class_or_union_diff::priv::{dms_replaced_by_adms_,
	changed_var_sptrs_type dms_replaced_by_adms_ordered_}): Add new
	data members.
	(data_member_comp::compare_data_members): Factorize this out of ...
	(data_member_comp::operator()(decl_base_sptr&, decl_base_sptr&)):
	... this.
	(data_member_comp::operator()(changed_var_sptr&,
	changed_var_sptr&)): Add new member function.
	(sort_changed_data_members): Declare ...
	* src/abg-comparison.cc (sort_changed_data_members): ... new
	function.
	(get_default_harmless_categories_bitmap): Adjust to take the new
	abigail::comparison::HARMLESS_DATA_MEMBER_CHANGE_CATEGORY into
	account.
	(operator<<(ostream& o, diff_category c)): Likewise.
	(class_or_union_diff::ensure_lookup_tables_populated): Handle
	Handle the insertion of anonymous data members to replace existing
	data members.
	(class_or_union_diff::{data_members_replaced_by_adms,
	ordered_data_members_replaced_by_adms}): Define new accessors.
	(suppression_categorization_visitor::visit_end): Propagate the
	SUPPRESSION_CATEGORIZATION_VISITOR from changes to the type of the
	data member if the data member doesn't have real local changes.
	* src/abg-default-reporter.cc (default_reporter::report): Report
	about anonymous data members that replace data members.
	* src/abg-ir.cc (struct dm_context_rel::priv): Define new data
	structure.
	(dm_context_rel::{dm_context_rel, get_is_laid_out,
	set_is_laid_out, get_offset_in_bits, set_offset_in_bits,
	operator==, operator!=, get_anonymous_data_member,
	set_anonymous_data_member}): Define the member functions here as
	they are not inline anymore.
	(class_or_union::maybe_fixup_members_of_anon_data_member): Define
	new member function.
	(class_or_union::add_data_member): Use it.
	(get_first_non_anonymous_data_member, get_next_data_member)
	(get_absolute_data_member_offset)
	(find_data_member_from_anonymous_data_member): Define new
	functions.
	* src/abg-reporter-priv.h
	(maybe_report_data_members_replaced_by_anon_dm): Declare ...
	* src/abg-reporter-priv.cc
	(maybe_report_data_members_replaced_by_anon_dm): ... new function.
	* src/abg-leaf-reporter.cc (leaf_reporter::report): Report data
	members replaced by anonymous data members.
	* tests/data/test-diff-filter/test-PR25661-[1-6]-report-[1-4].txt: New
	test reference outputs.
	* tests/data/test-diff-filter/test-PR25661-[1-6]-v{0,1}.c: Test
	source code files.
	* tests/data/test-diff-filter/test-PR25661-[1-6]-v{0,1}.o: Test
	binary input files.
	* tests/data/Makefile.am: Add the new test files above to source
	distribution.
	* tests/test-diff-filter.cc (in_out_specs): Add the binary test
	inputs above to this test harness.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-report-0.txt:
	Adjust.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>
2020-05-18 13:42:50 +02:00
autoconf-archive Do not ignore valgrind checks returning an error 2017-02-27 10:01:15 +01:00
bash-completion Add --self-compare option in fedabipkgdiff 2017-05-31 16:21:14 +05:30
doc doc: Fix sufficient suppression property lists. 2020-05-13 12:11:11 +02:00
include Bug 25661 - Support data member replacement by anonymous data member 2020-05-18 13:42:50 +02:00
m4 Delete ltsugar.m4 and pkg.m4 files from m4/ 2015-01-06 09:54:45 +01:00
scripts Clean up scripts/* 2017-04-14 04:14:12 -04:00
src Bug 25661 - Support data member replacement by anonymous data member 2020-05-18 13:42:50 +02:00
tests Bug 25661 - Support data member replacement by anonymous data member 2020-05-18 13:42:50 +02:00
tools Add --no-write-default-sizes option. 2020-04-29 11:56:40 +02:00
.clang-format clang-format: set continuation indentation to 2 2020-05-18 10:48:09 +02:00
.gitignore .gitignore: Add libabigail-?.* *.orig files 2019-05-22 14:34:23 +02:00
abigail.m4 For usage from within GCC set header path to $includedir/libabigail 2013-08-14 16:10:15 +02:00
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VISIBILITY Control symbols exported from libabigail.so 2016-07-27 12:51:02 +02:00

This is the Application Binary Interface Generic Analysis and
Instrumentation Library.

It aims at constructing, manipulating, serializing and de-serializing
ABI-relevant artifacts.

The set of artifacts that we are intersted is made of quantities like
types, variable, fonctions and declarations of a given library or
program.  For a given library or program this set of quantities is
called an ABI corpus.

This library aims at (among other things) providing a way to compare
two ABI Corpora (apparently the plural of corpus is copora, heh,
that's cool), provide detailed information about their differences,
and help build tools to infer interesting conclusions about these
differences.

You are welcome to contribute to this project after reading the files
CONTRIBUTING and COMMIT-LOG-GUIDELINES files in the source tree.

Communicating with the maintainers of this project -- including
sending patches to be include to the source code -- happens via email
at libabigail@sourceware.org.