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0cd814766b
It turned out it's important to be able to suppress changes about
types that are reachable from a function parameter only through e.g, a
pointer or a reference, so that only changes types that are reachable
directly from a function parameter are emitted.
This patch adds that feature.
While doing this, I noticed this: Suppose a diff node D2 is marked as
being redundant with a diff node D1 seen previously. So only D1 is
reported; D2 is not, because it's been filtered out, because it's
redundant with D1. But then suppose D1 is filtered out, due to a
suppression specification. At that point, D2 should not be marked
redundant anymore, and should be reported.
Of course, the code before this patch was wrongly filtering D2 *and*
D1 out. So this patch fixes that.
* include/abg-comparison.h (enum type_suppression::reach_kind):
Define new enum.
(type_suppression::{get_consider_reach_kind,
set_consider_reach_kind, get_reach_kind,
mark_last_diff_visited_per_class_of_equivalence,
clear_last_diffs_visited_per_class_of_equivalence,
get_last_visited_diff_of_class_of_equivalence}): Declare new
member functions.
* src/abg-comparison.cc (diff_has_ancestor_filtered_out)
(read_suppression_reach_kind): Define static function.
(type_suppression::priv::{consider_reach_kind_, reach_kind_}):
Define new data members.
(type_suppression::priv::priv): Take a new reach_kind parameter.
(type_suppression::type_suppression): Adjust to new prototype of
priv constructor.
(type_suppression::{get_consider_reach_kind,
set_consider_reach_kind, get_reach_kind, set_reach_kind}): Define
new member functions.
(type_suppression::suppresses_diff): Interpret the result of
type_suppression::get_reach_kind() to determine if the suppression
specification suppresses a given diff node.
(read_type_suppression): Support reading the content of the
"accessed_through" property.
(diff_context::priv::last_visited_diff_node_): New data member.
(diff_context::{mark_last_diff_visited_per_class_of_equivalence,
clear_last_diffs_visited_per_class_of_equivalence,
get_last_visited_diff_of_class_of_equivalence}): Define new data
members.
(redundancy_marking_visitor::visit_begin): So if the current diff
node has already been visited, but if the previously visited node
has been filtered out, then do not mark this node as being
redundant. And mark the current diff node as being the last
visited one in its class of equivalence.
(categorize_redundancy): Clear the map of diff nodes visited per
class of equivalence.
* doc/manuals/libabigail-concepts.rst: Document the new
'accessed_through' property.
* tests/data/test-diff-suppr/test13-suppr-through-pointer-0.suppr:
New test input data.
* tests/data/test-diff-suppr/test13-suppr-through-pointer-report-{0,1}.txt:
Likewise.
* tests/data/test-diff-suppr/libtest13-suppr-through-pointer-v{0,1}.so:
New test input binaries.
* tests/data/test-diff-suppr/test13-suppr-through-pointer-v{0,1}.cc:
Source code of the test input binaries above.
* tests/data/test-diff-suppr/test14-suppr-non-redundant-0.suppr:
New test input data.
* tests/data/test-diff-suppr/test14-suppr-non-redundant-report-0.txt:
Likewise.
* tests/data/test-diff-suppr/test14-suppr-non-redundant-v{0,1}.o:
New test input binaries.
* tests/data/test-diff-suppr/test14-suppr-non-redundant-v{0,1}.cc:
Source code of the binaries above.
Signed-off-by: Dodji Seketeli <dodji@redhat.com>
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ReStructuredText
#########
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Concepts
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#########
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.. _abi_artifacts_label:
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ABI artifacts
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=============
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An ABI artifact is a relevant part of the ABI of a shared library or
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program. Examples of ABI artifacts are exported types, variables,
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functions, or `ELF`_ symbols exported by a shared library.
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.. _harmfulchangeconcept_label:
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Harmful changes
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===============
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A change in the diff report is considered harmful if it might cause
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ABI compatibility issues. That is, it might prevent an application
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dynamically linked against a given version of a library to keep
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working with the changed subsequent versions of the same library.
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.. _harmlesschangeconcept_label:
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Harmless changes
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================
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A change in the diff report is considered harmless if it will not
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cause any ABI compatibility issue. That is, it will not prevent an
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application dynamically linked against given version of a library to
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keep working with the changed subsequent versions of the same library.
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By default, ``abidiff`` filters harmless changes from the diff report.
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.. _suppr_spec_label:
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Suppression specifications
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==========================
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* Definition
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A suppression specification file is a way for a user to instruct
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:ref:`abidiff <abidiff_label>` to avoid emitting reports for changes
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involving certain :ref:`ABI artifacts<abi_artifacts_label>`.
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It contains directives (or specifications) that describe the set of
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ABI artifacts to avoid emitting change reports about.
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* Introductory examples
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Its syntax is based on a simplified and customized form of `Ini File
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Syntax`_. For instance, to specify that change reports on a type
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named FooPrivateType should be suppressed, one could write this
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suppression specification: ::
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[suppress_type]
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name = FooPrivateType
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Maybe we want to ensure that only a change reports about structures
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named FooPrivateType should be suppressed, one could write: ::
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[suppress_type]
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type_kind = struct
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name = FooPrivateType
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But we could also want to suppress change reports avoid typedefs named
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FooPrivateType. In that case we would write: ::
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[suppress_type]
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type_kind = typedef
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name = FooPrivateType
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Or, we could want to suppress change reports about all struct which
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names end with PrivateType: ::
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[suppress_type]
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type_kind = struct
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name_regexp = ^.*PrivateType
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Let's now look at the generic syntax of suppression specification
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files.
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* Syntax
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* Properties
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More generally, the format of suppression lists is organized
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around the concept of `property`. Every property has a name and
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a value, delimited by the ``=`` sign. E.g: ::
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name = value
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Leading and trailing white spaces are ignored around property
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name and values.
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.. _suppr_regexp_label:
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* Regular expressions
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The value of some properties might be a regular expression. In
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that case, they must comply with the syntax of `extended POSIX
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regular expressions
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<http://www.gnu.org/software/findutils/manual/html_node/find_html/posix_002dextended-regular-expression-syntax.html#posix_002dextended-regular-expression-syntax>`_.
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Note that Libabigail uses the regular expression engine of the
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`GNU C Library`_.
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* Escaping a character in a regular expression
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When trying to match a string that contains a ``*`` character,
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like in the pointer type ``int*``, one must be careful to notice
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that the character ``*`` is a special character in the extended
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POSIX regular expression syntax. And that character must be
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escaped for the regular expression engine. Thus the regular
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expression that would match the string ``int*`` in a suppression
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file should be ::
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int\\*
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Wait; but then why the two ``\`` characters? Well, because the
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``\`` character is a special character in the `Ini File Syntax`_
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used for specifying suppressions. So it must be escaped as
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well, so that the Ini File parser leaves a ``\`` character
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intact in the data stream that is handed to the regular
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expression engine. Hence the ``\\`` targeted at the Ini File
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parser.
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So, in short, to escape a character in a regular expression,
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always prefix the character with the ``\\`` sequence.
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* Sections
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Properties are then grouped into arbitrarily named sections that
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shall not be nested. The name of the section is on a line by
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itself and is surrounded by square brackets, i.e: ::
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[section_name]
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property1_name = property1_value
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property2_name = property2_value
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A section might or might not have properties. Sections that
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expect having properties and which are found nonetheless empty
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are just ignored. Properties that are not recognized by the
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reader are ignored as well.
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* Section names
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* ``[suppress_type]``
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Suppresses report messages about a type change. The potential
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properties of this sections are:
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* ``name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
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Suppresses change reports involving types whose name
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matches the regular expression specified as value of this
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property.
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* ``name`` ``=`` <a-value>
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Suppresses change reports involving types whose name
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equals the value of this property.
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* ``type_kind`` ``=`` ``class`` | ``struct`` | ``union`` |
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``enum`` | ``array`` | ``typedef`` | ``builtin``
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Suppresses change reports involving a certain kind of
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type. The kind of type to suppress change reports for is
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specified by the possible values listed above:
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- ``class``: suppress change reports for class types.
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Note that even if class types don't exist for C, this
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value still triggers the suppression of change reports
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for struct types, in C. In C++ however, it should do
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what it suggests.
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- ``struct``: suppress change reports for struct types
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in C or C++. Note that the value ``class`` above is a
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super-set of this one.
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- ``union``: suppress change reports for union types.
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- ``enum``: suppress change reports for enum types.
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- ``array``: suppress change reports for array types.
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- ``typedef``: suppress change reports for typedef types.
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- ``builtin``: suppress change reports for built-in (or
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native) types. Example of built-in types are char,
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int, unsigned int, etc.
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.. _suppr_has_data_member_inserted_at_label:
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* ``has_data_member_inserted_at`` ``=`` <``offset-in-bit``>
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Suppresses change reports involving a type which has at
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least one data member inserted at an offset specified by
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the property value ``offset-in-bit``. The value
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``offset-in-bit`` is either:
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- an integer value, expressed in bits, which denotes
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the offset of the insertion point of the data
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member, starting from the beginning of the relevant
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structure or class.
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- the keyword ``end`` which is a named constant which
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value equals the offset of the end of the of the
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structure or class.
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- the function call expression
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``offset_of(data-member-name)`` where
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`data-member-name` is the name of a given data
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member of the relevant structure or class. The
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value of this function call expression is an integer
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that represents the offset of the data member
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denoted by ``data-member-name``.
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- the function call expression
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``offset_after(data-member-name)`` where
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`data-member-name` is the name of a given data
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member of the relevant structure or class. The
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value of this function call expression is an integer
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that represents the offset of the point that comes
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right after the region occupied by the data member
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denoted by ``data-member-name``.
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.. _suppr_has_data_member_inserted_between_label:
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* ``has_data_member_inserted_between`` ``=`` {<``range-begin``>, <``range-end``>}
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Suppresses change reports involving a type which has at
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least one data member inserted at an offset that is
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comprised in the range between ``range-begin`` and
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``range-end``. Please note that each of the values
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``range-begin`` and ``range-end`` can be of the same form
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as for the :ref:`has_data_member_inserted_at
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<suppr_has_data_member_inserted_at_label>` property above.
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Usage examples of this properties are: ::
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has_data_member_inserted_between = {8, 64}
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or: ::
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has_data_member_inserted_between = {16, end}
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or: ::
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has_data_member_inserted_between = {offset_after(member1), end}
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.. _suppr_has_data_members_inserted_between_label:
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* ``has_data_members_inserted_between`` ``=`` {<sequence-of-ranges>}
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Suppresses change reports involving a type which has multiple
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data member inserted in various offset ranges. A usage
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example of this property is, for instance: ::
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has_data_members_inserted_between = {{8, 31}, {72, 95}}
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This usage example suppresses change reports involving a
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type which has data members inserted in bit offset ranges
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[8 31] and [72 95]. The length of the sequence of ranges
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or this ``has_data_members_inserted_between`` is not
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bounded; it can be as long as the system can cope with.
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The values of the boundaries of the ranges are of the same
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kind as for the :ref:`has_data_member_inserted_at
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<suppr_has_data_member_inserted_at_label>` property above.
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Another usage example of this property is thus: ::
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has_data_members_inserted_between =
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{
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{offset_after(member0), offset_of(member1)},
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{72, end}
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}
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.. _suppr_accessed_through_property_label:
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* ``accessed_through`` ``=`` <some-predefined-values>
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Suppress change reports involving a type which is referred
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to either directly or through a pointer or a reference.
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The potential values of this property are the predefined
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keywords below:
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* ``direct``
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So if the ``[suppress_type]`` contains the property
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description: ::
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accessed_through = direct
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then changes about a type that is referred-to
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directly (i.e, not through a pointer or a reference)
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are going to be suppressed.
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* ``pointer``
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If the ``accessed_through`` property is set to the
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value ``pointer`` then changes about a type that is
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referred-to through a pointer are going to be
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suppressed.
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* ``reference``
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If the ``accessed_through`` property is set to the
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value ``reference`` then changes about a type that is
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referred-to through a reference are going to be
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suppressed.
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* ``reference-or-pointer``
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If the ``accessed_through`` property is set to the
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value ``reference-or-pointer`` then changes about a
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type that is referred-to through either a reference
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or a pointer are going to be suppressed.
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For an extensive example of how to use this property,
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please check out the example below about :ref:`suppressing
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change reports about types accessed either directly or
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through pointers <example_accessed_through_label>`.
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.. _suppr_label_property_label:
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* ``label`` ``=`` <some-value>
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Define a label for the section. A label is just an
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informative string that might be used by abidiff to refer
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to a type suppression in error messages.
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* ``[suppress_function]``
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Suppresses report messages about changes on sub-types of a
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function. The potential properties of this sections are:
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* ``label`` ``=`` <some-value>
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This property is the same as the :ref:`label property
|
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<suppr_label_property_label>` defined above.
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* ``name`` ``=`` <some-value>
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Suppresses change reports involving functions whose name
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equals the value of this property.
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* ``name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
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Suppresses change reports involving functions whose name
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matches the regular expression specified as value of this
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property.
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* ``parameter`` ``=`` <function-parameter-specification>
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Suppresses change reports involving functions whose
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parameters match the parameter specification indicated as
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value of this property.
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The format of the function parameter specification is:
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``'`` ``<parameter-index>`` ``<space>`` ``<type-name-or-regular-expression>``
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That is, an apostrophe followed by a number that is the
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index of the parameter, followed by one of several spaces,
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followed by either the name of the type of the parameter,
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or a regular expression describing a family of parameter
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type names.
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If the parameter type name is designated by a regular
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expression, then said regular expression must be enclosed
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between two slashes; like ``/some-regular-expression/``.
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The index of the first parameter of the function is zero.
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Note that for member functions (methods of classes), the
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this is the first parameter that comes after the implicit
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"this" pointer parameter.
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Examples of function parameter specifications are: ::
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'0 int
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Which means, the parameter at index 0, whose type name is
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``int``. ::
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'4 unsigned char*
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Which means, the parameter at index 4, whose type name is
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``unsigned char*``. ::
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'2 /^foo.*&/
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Which means, the parameter at index 2, whose type name
|
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starts with the string "foo" and ends with an '&'. In
|
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other words, this is the third parameter and it's a
|
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reference on a type that starts with the string "foo".
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* ``return_type_name`` ``=`` <some-value>
|
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Suppresses change reports involving functions whose return
|
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type name equals the value of this property.
|
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* ``return_type_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
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Suppresses change reports involving functions whose return
|
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type name matches the regular expression specified as
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value of this property.
|
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* ``symbol_name`` ``=`` <some-value>
|
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Suppresses change reports involving functions whose symbol
|
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name equals the value of this property.
|
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* ``symbol_name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
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Suppresses change reports involving functions whose symbol
|
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name matches the regular expression specified as value of
|
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this property.
|
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* ``symbol_version`` ``=`` <some-value>
|
|
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Suppresses change reports involving functions whose symbol
|
|
version equals the value of this property.
|
|
|
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* ``symbol_version_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
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|
|
Suppresses change reports involving functions whose symbol
|
|
version matches the regular expression specified as value
|
|
of this property.
|
|
|
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* ``[suppress_variable]``
|
|
|
|
Suppresses report messages about changes on sub-types of a
|
|
variable. The potential properties of this sections are:
|
|
|
|
* ``label`` ``=`` <some-value>
|
|
|
|
This property is the same as the :ref:`label property
|
|
<suppr_label_property_label>` defined above.
|
|
|
|
* ``name`` ``=`` <some-value>
|
|
|
|
Suppresses change reports involving variables whose name
|
|
equals the value of this property.
|
|
|
|
* ``name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
|
|
|
Suppresses change reports involving variables whose name
|
|
matches the regular expression specified as value of this
|
|
property.
|
|
|
|
* ``symbol_name`` ``=`` <some-value>
|
|
|
|
Suppresses change reports involving variables whose symbol
|
|
name equals the value of this property.
|
|
|
|
* ``symbol_name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
|
|
|
Suppresses change reports involving variables whose symbol
|
|
name matches the regular expression specified as value of
|
|
this property.
|
|
|
|
* ``symbol_version`` ``=`` <some-value>
|
|
|
|
Suppresses change reports involving variables whose symbol
|
|
version equals the value of this property.
|
|
|
|
* ``symbol_version_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
|
|
|
Suppresses change reports involving variables whose symbol
|
|
version matches the regular expression specified as value
|
|
of this property.
|
|
|
|
* ``type_name`` ``=`` <some-value>
|
|
|
|
Suppresses change reports involving variables whose type
|
|
name equals the value of this property.
|
|
|
|
* ``type_name_regexp`` ``=`` <:ref:`regular-expression <suppr_regexp_label>`>
|
|
|
|
Suppresses change reports involving variables whose type
|
|
name matches the regular expression specified as value of
|
|
this property.
|
|
|
|
* Comments
|
|
|
|
``;`` or ``#`` ASCII character at the beginning of a line
|
|
indicates a comment. Comment lines are ignored.
|
|
|
|
* Code examples
|
|
|
|
1. Suppressing change reports about types.
|
|
|
|
Suppose we have a library named ``libtest1-v0.so`` which
|
|
contains this very useful code: ::
|
|
|
|
$ cat -n test1-v0.cc
|
|
1 // A forward declaration for a type considered to be opaque to
|
|
2 // function foo() below.
|
|
3 struct opaque_type;
|
|
4
|
|
5 // This function cannot touch any member of opaque_type. Hence,
|
|
6 // changes to members of opaque_type should not impact foo, as far as
|
|
7 // ABI is concerned.
|
|
8 void
|
|
9 foo(opaque_type*)
|
|
10 {
|
|
11 }
|
|
12
|
|
13 struct opaque_type
|
|
14 {
|
|
15 int member0;
|
|
16 char member1;
|
|
17 };
|
|
$
|
|
|
|
Let's change the layout of struct opaque_type by inserting a data
|
|
member around line 15, leading to a new version of the library,
|
|
that we shall name ``libtest1-v1.so``: ::
|
|
|
|
$ cat -n test1-v1.cc
|
|
1 // A forward declaration for a type considered to be opaque to
|
|
2 // function foo() below.
|
|
3 struct opaque_type;
|
|
4
|
|
5 // This function cannot touch any member of opaque_type; Hence,
|
|
6 // changes to members of opaque_type should not impact foo, as far as
|
|
7 // ABI is concerned.
|
|
8 void
|
|
9 foo(opaque_type*)
|
|
10 {
|
|
11 }
|
|
12
|
|
13 struct opaque_type
|
|
14 {
|
|
15 char added_member; // <-- a new member got added here now.
|
|
16 int member0;
|
|
17 char member1;
|
|
18 };
|
|
$
|
|
|
|
Let's compile both examples. We shall not forget to compile them
|
|
with debug information generation turned on: ::
|
|
|
|
$ g++ -shared -g -Wall -o libtest1-v0.so test1-v0.cc
|
|
$ g++ -shared -g -Wall -o libtest1-v1.so test1-v1.cc
|
|
|
|
Let's ask :ref:`abidiff <abidiff_label>` which ABI differences it sees
|
|
between ``libtest1-v0.so`` and ``libtest1-v1.so``: ::
|
|
|
|
$ abidiff libtest1-v0.so libtest1-v1.so
|
|
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(opaque_type*)' has some indirect sub-type changes:
|
|
parameter 0 of type 'opaque_type*' has sub-type changes:
|
|
in pointed to type 'struct opaque_type':
|
|
size changed from 64 to 96 bits
|
|
1 data member insertion:
|
|
'char opaque_type::added_member', at offset 0 (in bits)
|
|
2 data member changes:
|
|
'int opaque_type::member0' offset changed from 0 to 32
|
|
'char opaque_type::member1' offset changed from 32 to 64
|
|
|
|
|
|
So ``abidiff`` reports that the opaque_type's layout has changed
|
|
in a significant way, as far as ABI implications are concerned, in
|
|
theory. After all, a sub-type (``struct opaque_type``) of an
|
|
exported function (``foo()``) has seen its layout change. This
|
|
might have non negligible ABI implications. But in practice here,
|
|
the programmer of the litest1-v1.so library knows that the "soft"
|
|
contract between the function ``foo()`` and the type ``struct
|
|
opaque_type`` is to stay away from the data members of the type.
|
|
So layout changes of ``struct opaque_type`` should not impact
|
|
``foo()``.
|
|
|
|
Now to teach ``abidiff`` about this soft contract and have it
|
|
avoid emitting what amounts to false positives in this case, we
|
|
write the suppression specification file below: ::
|
|
|
|
$ cat test1.suppr
|
|
[suppress_type]
|
|
type_kind = struct
|
|
name = opaque_type
|
|
|
|
Translated in plain English, this suppression specification would
|
|
read: "Do not emit change reports about a struct which name is
|
|
opaque_type".
|
|
|
|
Let's now invoke ``abidiff`` on the two versions of the library
|
|
again, but this time with the suppression specification: ::
|
|
|
|
$ abidiff --suppressions test1.suppr libtest1-v0.so libtest1-v1.so
|
|
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
As you can see, ``abidiff`` does not report the change anymore; it
|
|
tells us that it was filtered out instead.
|
|
|
|
2. Suppressing change reports about types with data member
|
|
insertions
|
|
|
|
Suppose the first version of a library named ``libtest3-v0.so``
|
|
has this source code: ::
|
|
|
|
/* Compile this with:
|
|
gcc -g -Wall -shared -o libtest3-v0.so test3-v0.c
|
|
*/
|
|
|
|
struct S
|
|
{
|
|
char member0;
|
|
int member1; /*
|
|
between member1 and member2, there is some padding,
|
|
at least on some popular platforms. On
|
|
these platforms, adding a small enough data
|
|
member into that padding shouldn't change
|
|
the offset of member1. Right?
|
|
*/
|
|
};
|
|
|
|
int
|
|
foo(struct S* s)
|
|
{
|
|
return s->member0 + s->member1;
|
|
}
|
|
|
|
Now, suppose the second version of the library named
|
|
``libtest3-v1.so`` has this source code in which a data member
|
|
has been added in the padding space of struct S and another data
|
|
member has been added at its end: ::
|
|
|
|
/* Compile this with:
|
|
gcc -g -Wall -shared -o libtest3-v1.so test3-v1.c
|
|
*/
|
|
|
|
struct S
|
|
{
|
|
char member0;
|
|
char inserted1; /* <---- A data member has been added here... */
|
|
int member1;
|
|
char inserted2; /* <---- ... and another one has been added here. */
|
|
};
|
|
|
|
int
|
|
foo(struct S* s)
|
|
{
|
|
return s->member0 + s->member1;
|
|
}
|
|
|
|
In ``libtest3-v1.so`` adding char data members ``S::inserted1``
|
|
and ``S::inserted2`` can be considered harmless (from an ABI
|
|
compatibility perspective), at least on the x86 platform, because
|
|
that doesn't change the offsets of the data members S::member0
|
|
and S::member1. But then running ``abidiff` on these two
|
|
versions of library yields: ::
|
|
|
|
$ abidiff libtest3-v0.so libtest3-v1.so
|
|
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 int foo(S*)' has some indirect sub-type changes:
|
|
parameter 0 of type 'S*' has sub-type changes:
|
|
in pointed to type 'struct S':
|
|
type size changed from 64 to 96 bits
|
|
2 data member insertions:
|
|
'char S::inserted1', at offset 8 (in bits)
|
|
'char S::inserted2', at offset 64 (in bits)
|
|
$
|
|
|
|
|
|
|
|
That is, ``abidiff`` shows us the two changes, even though we (the
|
|
developers of that very involved library) know that these changes
|
|
are harmless in this particular context.
|
|
|
|
Luckily, we can devise a suppression specification that essentially
|
|
tells abidiff to filter out change reports about adding a data
|
|
member between ``S::member0`` and ``S::member1``, and adding a data
|
|
member at the end of struct S. We have written such a suppression
|
|
specification in a file called test3-1.suppr and it unsurprisingly
|
|
looks like: ::
|
|
|
|
[suppress_type]
|
|
name = S
|
|
has_data_member_inserted_between = {offset_after(member0), offset_of(member1)}
|
|
has_data_member_inserted_at = end
|
|
|
|
|
|
Now running ``abidiff`` with this suppression specification yields: ::
|
|
|
|
$ ../build/tools/abidiff --suppressions test3-1.suppr libtest3-v0.so libtest3-v1.so
|
|
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
$
|
|
|
|
|
|
Hooora! \\o/ (I guess)
|
|
|
|
.. _example_accessed_through_label:
|
|
3. Suppressing change reports about types accessed either directly
|
|
or through pointers
|
|
|
|
Suppose we have a first version of an object file which source
|
|
code is the file widget-v0.cc below: ::
|
|
|
|
// Compile with: g++ -g -c widget-v0.cc
|
|
|
|
struct widget
|
|
{
|
|
int x;
|
|
int y;
|
|
|
|
widget()
|
|
:x(), y()
|
|
{}
|
|
};
|
|
|
|
void
|
|
fun0(widget*)
|
|
{
|
|
// .. do stuff here.
|
|
}
|
|
|
|
void
|
|
fun1(widget&)
|
|
{
|
|
// .. do stuff here ..
|
|
}
|
|
|
|
void
|
|
fun2(widget w)
|
|
{
|
|
// ... do other stuff here ...
|
|
}
|
|
|
|
Now suppose in the second version of that file, named
|
|
widget-v1.cc, we have added some data members at the end of
|
|
the type ``struct widget``; here is what the content of that file
|
|
would look like: ::
|
|
|
|
// Compile with: g++ -g -c widget-v1.cc
|
|
|
|
struct widget
|
|
{
|
|
int x;
|
|
int y;
|
|
int w; // We have added these two new data members here ..
|
|
int h; // ... and here.
|
|
|
|
widget()
|
|
: x(), y(), w(), h()
|
|
{}
|
|
};
|
|
|
|
void
|
|
fun0(widget*)
|
|
{
|
|
// .. do stuff here.
|
|
}
|
|
|
|
void
|
|
fun1(widget&)
|
|
{
|
|
// .. do stuff here ..
|
|
}
|
|
|
|
void
|
|
fun2(widget w)
|
|
{
|
|
// ... do other stuff here ...
|
|
}
|
|
|
|
When we invoke ``abidiff`` on the object files resulting from the
|
|
compilation of the two file above, here is what we get: ::
|
|
|
|
$ abidiff widget-v0.o widget-v1.o
|
|
Functions changes summary: 0 Removed, 2 Changed (1 filtered out), 0 Added functions
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
2 functions with some indirect sub-type change:
|
|
|
|
[C]'function void fun0(widget*)' has some indirect sub-type changes:
|
|
parameter 1 of type 'widget*' has sub-type changes:
|
|
in pointed to type 'struct widget':
|
|
type size changed from 64 to 128 bits
|
|
2 data member insertions:
|
|
'int widget::w', at offset 64 (in bits)
|
|
'int widget::h', at offset 96 (in bits)
|
|
|
|
[C]'function void fun2(widget)' has some indirect sub-type changes:
|
|
parameter 1 of type 'struct widget' has sub-type changes:
|
|
details were reported earlier
|
|
$
|
|
|
|
I guess a little bit of explaining is due here. ``abidiff``
|
|
detects that two data member got added at the end of ``struct
|
|
widget``. it also tells us that the type change impacts the
|
|
exported function ``fun0()`` which uses the type ``struct
|
|
widget`` through a pointer, in its signature.
|
|
|
|
Careful readers will notice that the change to ``struct widget``
|
|
also impacts the exported function ``fun1()``, that uses type
|
|
``struct widget`` through a reference. But then ``abidiff``
|
|
doesn't tell us about the impact on that function ``fun1()``
|
|
because it has evaluated that change as being **redundant** with
|
|
the change it reported on ``fun0()``. It has thus filtered it
|
|
out, to avoid cluttering the output with noise.
|
|
|
|
Redundancy detection and filtering is fine and helpful to avoid
|
|
burying the important information in a sea of noise. However, it
|
|
must be treated with care, by fear of mistakenly filtering out
|
|
relevant and important information.
|
|
|
|
That is why ``abidiff`` tells us about the impact that the change
|
|
to ``struct widget`` has on function ``fun2()``. In this case,
|
|
that function uses the type ``struct widget`` **directly** (in
|
|
its signature). It does not use it via a pointer or a reference.
|
|
In this case, the direct use of this type causes ``fun2()`` to be
|
|
exposed to a potentially harmful ABI change. Hence, the report
|
|
about ``fun2()`` is not filtered out, even though it's about that
|
|
same change on ``struct widget``.
|
|
|
|
To go further in suppressing reports about changes that are
|
|
harmless and keeping only those that we know are harmful, we
|
|
would like to go tell abidiff to suppress reports about this
|
|
particular ``struct widget`` change when it impacts uses of
|
|
``struct widget`` through a pointer or reference. In other
|
|
words, suppress the change reports about ``fun0()`` **and**
|
|
``fun1()``. We would then write this suppression specification,
|
|
in file ``widget.suppr``: ::
|
|
|
|
[suppress_type]
|
|
name = widget
|
|
type_kind = struct
|
|
has_data_member_inserted_at = end
|
|
accessed_through = reference-or-pointer
|
|
|
|
# So this suppression specification says to suppress reports about
|
|
# the type 'struct widget', if this type was added some data member
|
|
# at its end, and if the change impacts uses of the type through a
|
|
# reference or a pointer.
|
|
|
|
Invoking ``abidiff`` on ``widget-v0.o`` and ``widget-v1.o`` with
|
|
this suppression specification yields: ::
|
|
|
|
$ abidiff --suppressions widget.suppr widget-v0.o widget-v1.o
|
|
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
1 function with some indirect sub-type change:
|
|
|
|
[C]'function void fun2(widget)' has some indirect sub-type changes:
|
|
parameter 1 of type 'struct widget' has sub-type changes:
|
|
type size changed from 64 to 128 bits
|
|
2 data member insertions:
|
|
'int widget::w', at offset 64 (in bits)
|
|
'int widget::h', at offset 96 (in bits)
|
|
$
|
|
|
|
As expected, I guess.
|
|
|
|
4. Suppressing change reports about functions.
|
|
|
|
Suppose we have a first version a library named
|
|
``libtest2-v0.so`` whose source code is: ::
|
|
|
|
$ cat -n test2-v0.cc
|
|
|
|
1 struct S1
|
|
2 {
|
|
3 int m0;
|
|
4
|
|
5 S1()
|
|
6 : m0()
|
|
7 {}
|
|
8 };
|
|
9
|
|
10 struct S2
|
|
11 {
|
|
12 int m0;
|
|
13
|
|
14 S2()
|
|
15 : m0()
|
|
16 {}
|
|
17 };
|
|
18
|
|
19 struct S3
|
|
20 {
|
|
21 int m0;
|
|
22
|
|
23 S3()
|
|
24 : m0()
|
|
25 {}
|
|
26 };
|
|
27
|
|
28 int
|
|
29 func(S1&)
|
|
30 {
|
|
31 // suppose the code does something with the argument.
|
|
32 return 0;
|
|
33
|
|
34 }
|
|
35
|
|
36 char
|
|
37 func(S2*)
|
|
38 {
|
|
39 // suppose the code does something with the argument.
|
|
40 return 0;
|
|
41 }
|
|
42
|
|
43 unsigned
|
|
44 func(S3)
|
|
45 {
|
|
46 // suppose the code does something with the argument.
|
|
47 return 0;
|
|
48 }
|
|
$
|
|
|
|
And then we come up with a second version ``libtest2-v1.so`` of
|
|
that library; the source code is modified by making the
|
|
structures ``S1``, ``S2``, ``S3`` inherit another struct: ::
|
|
|
|
$ cat -n test2-v1.cc
|
|
1 struct base_type
|
|
2 {
|
|
3 int m_inserted;
|
|
4 };
|
|
5
|
|
6 struct S1 : public base_type // <--- S1 now has base_type as its base
|
|
7 // type.
|
|
8 {
|
|
9 int m0;
|
|
10
|
|
11 S1()
|
|
12 : m0()
|
|
13 {}
|
|
14 };
|
|
15
|
|
16 struct S2 : public base_type // <--- S2 now has base_type as its base
|
|
17 // type.
|
|
18 {
|
|
19 int m0;
|
|
20
|
|
21 S2()
|
|
22 : m0()
|
|
23 {}
|
|
24 };
|
|
25
|
|
26 struct S3 : public base_type // <--- S3 now has base_type as its base
|
|
27 // type.
|
|
28 {
|
|
29 int m0;
|
|
30
|
|
31 S3()
|
|
32 : m0()
|
|
33 {}
|
|
34 };
|
|
35
|
|
36 int
|
|
37 func(S1&)
|
|
38 {
|
|
39 // suppose the code does something with the argument.
|
|
40 return 0;
|
|
41
|
|
42 }
|
|
43
|
|
44 char
|
|
45 func(S2*)
|
|
46 {
|
|
47 // suppose the code does something with the argument.
|
|
48 return 0;
|
|
49 }
|
|
50
|
|
51 unsigned
|
|
52 func(S3)
|
|
53 {
|
|
54 // suppose the code does something with the argument.
|
|
55 return 0;
|
|
56 }
|
|
$
|
|
|
|
Now let's build the two libraries: ::
|
|
|
|
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
|
|
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
|
|
|
|
Let's look at the output of ``abidiff``: ::
|
|
|
|
$ abidiff libtest2-v0.so libtest2-v1.so
|
|
Functions changes summary: 0 Removed, 3 Changed, 0 Added functions
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
3 functions with some indirect sub-type change:
|
|
|
|
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
|
|
parameter 0 of type 'struct S3' has sub-type changes:
|
|
size changed from 32 to 64 bits
|
|
1 base class insertion:
|
|
struct base_type
|
|
1 data member change:
|
|
'int S3::m0' offset changed from 0 to 32
|
|
|
|
[C]'function char func(S2*)' has some indirect sub-type changes:
|
|
parameter 0 of type 'S2*' has sub-type changes:
|
|
in pointed to type 'struct S2':
|
|
size changed from 32 to 64 bits
|
|
1 base class insertion:
|
|
struct base_type
|
|
1 data member change:
|
|
'int S2::m0' offset changed from 0 to 32
|
|
|
|
[C]'function int func(S1&)' has some indirect sub-type changes:
|
|
parameter 0 of type 'S1&' has sub-type changes:
|
|
in referenced type 'struct S1':
|
|
size changed from 32 to 64 bits
|
|
1 base class insertion:
|
|
struct base_type
|
|
1 data member change:
|
|
'int S1::m0' offset changed from 0 to 32
|
|
$
|
|
|
|
Let's tell ``abidiff`` to avoid showing us the differences on the
|
|
overloads of ``func`` that takes either a pointer or a reference.
|
|
For that, we author this simple suppression specification: ::
|
|
|
|
$ cat -n libtest2.suppr
|
|
1 [suppress_function]
|
|
2 name = func
|
|
3 parameter = '0 S1&
|
|
4
|
|
5 [suppress_function]
|
|
6 name = func
|
|
7 parameter = '0 S2*
|
|
$
|
|
|
|
And then let's invoke ``abidiff`` with the suppression
|
|
specification: ::
|
|
|
|
$ ../build/tools/abidiff --suppressions libtest2.suppr libtest2-v0.so libtest2-v1.so
|
|
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
1 function with some indirect sub-type change:
|
|
|
|
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
|
|
parameter 0 of type 'struct S3' has sub-type changes:
|
|
size changed from 32 to 64 bits
|
|
1 base class insertion:
|
|
struct base_type
|
|
1 data member change:
|
|
'int S3::m0' offset changed from 0 to 32
|
|
|
|
|
|
The suppression specification could be reduced using
|
|
:ref:`regular expressions <suppr_regexp_label>`: ::
|
|
|
|
$ cat -n libtest2-1.suppr
|
|
1 [suppress_function]
|
|
2 name = func
|
|
3 parameter = '0 /^S.(&|\\*)/
|
|
$
|
|
|
|
$ ../build/tools/abidiff --suppressions libtest2-1.suppr libtest2-v0.so libtest2-v1.so
|
|
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
|
|
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
|
|
|
|
1 function with some indirect sub-type change:
|
|
|
|
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
|
|
parameter 0 of type 'struct S3' has sub-type changes:
|
|
size changed from 32 to 64 bits
|
|
1 base class insertion:
|
|
struct base_type
|
|
1 data member change:
|
|
'int S3::m0' offset changed from 0 to 32
|
|
|
|
$
|
|
|
|
.. _ELF: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
|
|
|
|
.. _Ini File Syntax: http://en.wikipedia.org/wiki/INI_file
|
|
|
|
.. _GNU C Library: http://www.gnu.org/software/libc
|