Provided by: abigail-doc_1.0~rc3-1_all 
NAME
libabigail - Library to analyze and compare ELF ABIs
OVERVIEW OF LIBABIGAIL
Libabigail stands for the Application Binary Interface Generic Analysis and
Instrumentation Library.
It aims at helping developers and software distributors to spot some ABI-related issues
like interface incompatibility in ELF shared libraries.
The type of interface incompatibilities that libabigail focuses on is related to changes
on the exported ELF functions and variables symbols, as well as layout and size changes of
data types of the functions and variables exported by shared libraries.
In other words, if the return type of a function exported by a shared library changes in
an incompatible way from one version of a given shared library to another, we want
libabigail to help people catch that.
In more concrete terms, libabigail can parse a shared library in ELF format, accompanied
with its associated debug information in DWARF format, build an internal representation of
all the functions and variables it exports, along with their types. It also builds an
internal representation of the ELF symbols of these functions and variables. That
information about these exported functions and variables is roughly what we consider as
being the ABI of the shared library, at least, in the scope of Libabigail.
Aside of this internal representation, libabigail provides facilities to perform deep
comparisons of two ABIs. That is, it can compare the types of two sets of functions or
variables and represents the result in a way that allows it to emit textual reports about
the differences.
This allows us to write tools like abidiff that can compare the ABI of two shared
libraries and represent the result in a meaningful enough way to help us spot ABI
incompatibilities.
TOOLS
Overview
The upstream code repository of Libabigail contains several tools written using the
library. They are maintained and released as part of the project. All tools come with a
bash-completion script.
Tools manuals
abidiff
abidiff compares the Application Binary Interfaces (ABI) of two shared libraries in ELF
format. It emits a meaningful report describing the differences between the two ABIs.
For a comprehensive ABI change report that includes changes about function and variable
sub-types, the two input shared libraries must be accompanied with their debug information
in DWARF format. Otherwise, only ELF symbols that were added or removed are reported.
Invocation
abidiff [options] <first-shared-library> <second-shared-library>
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --debug-info-dir1 | --d1 <di-path1>
For cases where the debug information for first-shared-library is split out into a
separate file, tells abidiff where to find that separate debug information file.
Note that di-path must point to the root directory under which the debug information
is arranged in a tree-like manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
Note also that this option is not mandatory for split debug information installed by
your system's package manager because then abidiff knows where to find it.
• --debug-info-dir2 | --d2 <di-path2>
Like --debug-info-dir1, this options tells abidiff where to find the split debug
information for the second-shared-library file.
• --stat
Rather than displaying the detailed ABI differences between first-shared-library and
second-shared-library, just display some summary statistics about these differences.
• --symtabs
Only display the symbol tables of the first-shared-library and second-shared-library.
• --deleted-fns
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the globally defined functions that got deleted
from first-shared-library.
• --changed-fns
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the changes in sub-types of the global functions
defined in first-shared-library.
• --added-fns
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the globally defined functions that were added to
second-shared-library.
• --deleted-vars
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the globally defined variables that were deleted
from first-shared-library.
• --changed-vars
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the changes in the sub-types of the global
variables defined in first-shared-library
• --added-vars
In the resulting report about the differences between first-shared-library and
second-shared-library, only display the global variables that were added (defined) to
second-shared-library.
• --no-linkage-name
In the resulting report, do not display the linkage names of the added, removed, or
changed functions or variables.
• --no-show-locs
Do not show information about where in the second shared library the respective
type was changed.
• --no-unreferenced-symbols
In the resulting report, do not display change information about function and
variable symbols that are not referenced by any debug information. Note that for
these symbols not referenced by any debug information, the change information
displayed is either added or removed symbols.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at path-to-suppressions. Note that this
option can appear multiple times on the command line; all the suppression
specification files are then taken into account.
• --drop <regex>
When reading the first-shared-library and second-shared-library ELF input files, drop
the globally defined functions and variables which name match the regular expression
regex. As a result, no change involving these functions or variables will be emitted
in the diff report.
• --drop-fn <regex>
When reading the first-shared-library and second-shared-library ELF input files, drop
the globally defined functions which name match the regular expression regex. As a
result, no change involving these functions will be emitted in the diff report.
• --drop-var <regex>
When reading the first-shared-library and second-shared-library ELF input files, drop
the globally defined variables matching a the regular expression regex.
• --keep <regex>
When reading the first-shared-library and second-shared-library ELF input files, keep
the globally defined functions and variables which names match the regular expression
regex. All other functions and variables are dropped on the floor and will thus not
appear in the resulting diff report.
• --keep-fn <regex>
When reading the first-shared-library and second-shared-library ELF input files, keep
the globally defined functions which name match the regular expression regex. All
other functions are dropped on the floor and will thus not appear in the resulting
diff report.
• --keep-var <regex>
When reading the first-shared-library and second-shared-library ELF input files, keep
the globally defined which names match the regular expression regex. All other
variables are dropped on the floor and will thus not appear in the resulting diff
report.
• --harmless
In the diff report, display only the harmless changes. By default, the harmless
changes are filtered out of the diff report keep the clutter to a minimum and have a
greater change to spot real ABI issues.
• --no-harmful
In the diff report, do not display the harmful changes. By default, only the harmful
changes are displayed in diff report.
• --redundant
In the diff report, do display redundant changes. A redundant change is a change
that has been displayed elsewhere in the report.
• --no-redundant
In the diff report, do NOT display redundant changes. A redundant change is a change
that has been displayed elsewhere in the report. This option is switched on by
default.
• --no-architecture
Do not take architecture in account when comparing ABIs.
• --dump-diff-tree
After the diff report, emit a textual representation of the diff nodes tree used by
the comparison engine to represent the changed functions and variables. That
representation is emitted to the error output for debugging purposes. Note that
this diff tree is relevant only to functions and variables that have some sub-type
changes. Added or removed functions and variables do not have any diff nodes tree
associated to them.
• --stats
Emit statistics about various internal things.
• --verbose
Emit verbose logs about the progress of miscellaneous internal things.
Return values
The exit code of the abidiff command is either 0 if the ABI of the binaries being compared
are equal, or non-zero if they differ or if the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in which each bit has a
specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there was an error in the way
the user invoked the tool. It might be set, for instance, if the user invoked the tool
with an unknown command line switch, with a wrong number or argument, etc. If this bit is
set, then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI of the binaries being
compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE means the ABI of the
binaries compared are different in an incompatible way. If this bit is set, then the
ABIDIFF_ABI_CHANGE bit must be set as well. If the ABIDIFF_ABI_CHANGE is set and the
ABIDIFF_INCOMPATIBLE_CHANGE is NOT set, then it means that the ABIs being compared might
or might not be compatible. In that case, a human being needs to review the ABI changes
to decide if they are compatible or not.
The remaining bits are not used for the moment.
Usage examples
1. Detecting a change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0* /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct type_base
5 {
6 int inserted;
7 };
8
9 struct S0 : public type_base
10 {
11 int m0;
12 };
13
14 void
15 foo(S0* /*parameter_name*/)
16 {
17 // do something with parameter_name.
18 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-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(S0*)' has some indirect sub-type changes:
parameter 0 of type 'S0*' has sub-type changes:
in pointed to type 'struct S0':
size changed from 32 to 64 bits
1 base class insertion:
struct type_base
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
2. Detecting another change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 foo(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-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(S0&)' has some indirect sub-type changes:
parameter 0 of type 'S0&' has sub-type changes:
in referenced type 'struct S0':
size changed from 32 to 64 bits
1 data member insertion:
'char S0::inserted_member', at offset 0 (in bits)
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
3. Detecting that functions got removed or added to a library:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 bar(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 1 Removed, 0 Changed, 1 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 Removed function:
'function void foo(S0&)' {_Z3fooR2S0}
1 Added function:
'function void bar(S0&)' {_Z3barR2S0}
$
abipkgdiff
abipkgdiff compares the Application Binary Interfaces (ABI) of the ELF binaries contained
in two software packages. The software package formats currently supported are Deb, RPM,
tar archives (either compressed or not) and plain directories that contain binaries.
For a comprehensive ABI change report that includes changes about function and variable
sub-types, the two input packages must be accompanied with their debug information
packages that contain debug information in DWARF format.
Invocation
abipkgdiff [option] <package1> <package2>
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --debug-info-pkg1 | --d1 <path>
For cases where the debug information for package1 is split out into a separate file,
tells abipkgdiff where to find that separate debug information package.
• --debug-info-pkg2 | --d2 <path>
For cases where the debug information for package2 is split out into a separate file,
tells abipkgdiff where to find that separate debug information package.
• --dso-only
Compare ELF files that are shared libraries, only. Do not compare executable files,
for instance.
• --redundant
In the diff reports, do display redundant changes. A redundant change is a change
that has been displayed elsewhere in a given report.
• --no-linkage-name
In the resulting report, do not display the linkage names of the added, removed, or
changed functions or variables.
• --no-added-syms
Do not show the list of functions, variables, or any symbol that was added.
• --no-added-binaries
Do not show the list of binaries that got added to the second package.
Please note that the presence of such added binaries is not considered like an ABI
change by this tool; as such, it doesn't have any impact on the exit code of the
tool. It does only have an informational value. Removed binaries are, however,
considered as an ABI change.
• --no-abignore
Do not search the package2 for the presence of suppression files.
• --no-parallel
By default, abipkgdiff will use all the processors it has available to execute
concurrently. This option tells it not to extract packages or run comparisons in
parallel.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at path-to-suppressions. Note that this
option can appear multiple times on the command line; all the suppression
specification files are then taken into account.
• --no-show-locs
Do not show information about where in the second shared library the respective
type was changed.
• --fail-no-dbg
Make the program fail and return a non-zero exit code if couldn't read any of the
debug information that comes from the debug info packages that were given on the
command line. If no debug info package were provided on the command line then this
option is not active.
Note that the non-zero exit code returned by the program as a result of this option
is the constant ABIDIFF_ERROR. To know the numerical value of that constant, please
refer to the exit code documentation.
• --keep-tmp-files
Do not erase the temporary directory files that are created during the execution of
the tool.
• --verbose
Emit verbose progress messages.
Return value
The exit code of the abipkgdiff command is either 0 if the ABI of the binaries compared
are equal, or non-zero if they differ or if the tool encountered an error.
In the later case, the value of the exit code is the same as for the abidiff tool.
abicompat
abicompat checks that an application that links against a given shared library is still
ABI compatible with a subsequent version of that library. If the new version of the
library introduces an ABI incompatibility, then abicompat hints the user at what exactly
that incompatibility is.
Invocation
abicompat [options] [<application> <shared-library-first-version> <shared-library-second-version>]
Options
• --help
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --list-undefined-symbols | -u
Display the list of undefined symbols of the application and exit.
• --show-base-names | -b
In the resulting report emitted by the tool, this option makes the application and
libraries be referred to by their base names only; not by a full absolute name. This
can be useful for use in scripts that wants to compare names of the application and
libraries independently of what their directory names are.
• --app-debug-info-dir <path-to-app-debug-info-directory>
Set the path to the directory under which the debug information of the application is
supposed to be laid out. This is useful for application binaries for which the debug
info is in a separate set of files.
• --lib-debug-info-dir1 <path-to-lib1-debug-info>
Set the path to the directory under which the debug information of the first version
of the shared library is supposed to be laid out. This is useful for shared library
binaries for which the debug info is in a separate set of files.
• --lib-debug-info-dir2 <path-to-lib1-debug-info>
Set the path to the directory under which the debug information of the second version
of the shared library is supposed to be laid out. This is useful for shared library
binaries for which the debug info is in a separate set of files.
• --no-show-locs
Do not show information about where in the second shared library the respective
type was changed.
• --weak-mode
This triggers the weak mode of abicompat. In this mode, only one version of the
library is required. That is, abicompat is invoked like this:
abicompat --weak-mode <the-application> <the-library>
Note that the --weak-mode option can even be omitted if only one version of the
library is given, along with the application; in that case, abicompat automatically
switches to operate in weak mode:
abicompat <the-application> <the-library>
In this weak mode, the types of functions and variables exported by the library and
consumed by the application (as in, the symbols of the these functions and variables
are undefined in the application and are defined and exported by the library) are
compared to the version of these types as expected by the application. And if these
two versions of types are different, abicompat tells the user what the differences
are.
In other words, in this mode, abicompat checks that the types of the functions and
variables exported by the library mean the same thing as what the application
expects, as far as the ABI is concerned.
Note that in this mode, abicompat doesn't detect exported functions or variables
(symbols) that are expected by the application but that are removed from the library.
That is why it is called weak mode.
Return values
The exit code of the abicompat command is either 0 if the ABI of the binaries being
compared are equal, or non-zero if they differ or if the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in which each bit has a
specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there was an error in the way
the user invoked the tool. It might be set, for instance, if the user invoked the tool
with an unknown command line switch, with a wrong number or argument, etc. If this bit is
set, then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI of the binaries being
compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE means the ABI of the
binaries compared are different in an incompatible way. If this bit is set, then the
ABIDIFF_ABI_CHANGE bit must be set as well. If the ABIDIFF_ABI_CHANGE is set and the
ABIDIFF_INCOMPATIBLE_CHANGE is NOT set, then it means that the ABIs being compared might
or might not be compatible. In that case, a human being needs to review the ABI changes
to decide if they are compatible or not.
The remaining bits are not used for the moment.
Usage examples
• Detecting a possible ABI incompatibility in a new shared library version:
$ cat -n test0.h
1 struct foo
2 {
3 int m0;
4
5 foo()
6 : m0()
7 {}
8 };
9
10 foo*
11 first_func();
12
13 void
14 second_func(foo&);
15
16 void
17 third_func();
$
$ cat -n test-app.cc
1 // Compile with:
2 // g++ -g -Wall -o test-app -L. -ltest-0 test-app.cc
3
4 #include "test0.h"
5
6 int
7 main()
8 {
9 foo* f = first_func();
10 second_func(*f);
11 return 0;
12 }
$
$ cat -n test0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-0.so test0.cc
3
4 #include "test0.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 void
19 third_func()
20 {
21 }
$
$ cat -n test1.h
1 struct foo
2 {
3 int m0;
4 char m1; /* <-- a new member got added here! */
5
6 foo()
7 : m0(),
8 m1()
9 {}
10 };
11
12 foo*
13 first_func();
14
15 void
16 second_func(foo&);
17
18 void
19 third_func();
$
$ cat -n test1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-1.so test1.cc
3
4 #include "test1.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 /* Let's comment out the definition of third_func()
19 void
20 third_func()
21 {
22 }
23 */
$
• Compile the first and second versions of the libraries: libtest-0.so and
libtest-1.so:
$ g++ -g -Wall -shared -o libtest-0.so test0.cc
$ g++ -g -Wall -shared -o libtest-1.so test1.cc
• Compile the application and link it against the first version of the library,
creating the test-app binary:
$ g++ -g -Wall -o test-app -L. -ltest-0.so test-app.cc
• Now, use abicompat to see if libtest-1.so is ABI compatible with app, with respect
to the ABI of libtest-0.so:
$ abicompat test-app libtest-0.so libtest-1.so
ELF file 'test-app' might not be ABI compatible with 'libtest-1.so' due to differences with 'libtest-0.so' below:
Functions changes summary: 0 Removed, 2 Changed, 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
2 functions with some indirect sub-type change:
[C]'function foo* first_func()' has some indirect sub-type changes:
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
[C]'function void second_func(foo&)' has some indirect sub-type changes:
parameter 0 of type 'foo&' has sub-type changes:
referenced type 'struct foo' changed, as reported earlier
$
• Now use the weak mode of abicompat, that is, providing just the application and the
new version of the library:
$ abicompat --weak-mode test-app libtest-1.so
functions defined in library
'libtest-1.so'
have sub-types that are different from what application
'test-app'
expects:
function foo* first_func():
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
$
abidw
abidw reads a shared library in ELF format and emits an XML representation of its ABI to
standard output. The emitted representation includes all the globally defined functions
and variables, along with a complete representation of their types. It also includes a
representation of the globally defined ELF symbols of the file. The input shared library
must contain associated debug information in DWARF format.
Invocation
abidw [options] [<path-to-elf-file>]
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --debug-info-dir | -d <dir-path>
In cases where the debug info for path-to-elf-file is in a separate file that is
located in a non-standard place, this tells abidw where to look for that debug info
file.
Note that dir-path must point to the root directory under which the debug information
is arranged in a tree-like manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
Note that this option is not mandatory for split debug information installed by your
system's package manager because then abidw knows where to find it.
• --out-file <file-path>
This option instructs abidw to emit the XML representation of path-to-elf-file into
the file file-path, rather than emitting it to its standard output.
• --noout
This option instructs abidw to not emit the XML representation of the ABI. So it
only reads the ELF and debug information, builds the internal representation of the
ABI and exits. This option is usually useful for debugging purposes.
• --check-alternate-debug-info <elf-path>
If the debug info for the file elf-path contains a reference to an alternate debug
info file, abidw checks that it can find that alternate debug info file. In that
case, it emits a meaningful success message mentioning the full path to the alternate
debug info file found. Otherwise, it emits an error code.
• --no-show-locs
Do not show information about where in the second shared library the respective
type was changed.
• --check-alternate-debug-info-base-name <elf-path>
Like --check-alternate-debug-info, but in the success message, only mention the base
name of the debug info file; not its full path.
• --load-all-types
By default, libabigail (and thus abidw) only loads types that are reachable from
functions and variables declarations that are publicly defined and exported by the
binary. So only those types are present in the output of abidw. This option however
makes abidw load all the types defined in the binaries, even those that are not
reachable from public declarations.
• --abidiff
Load the ABI of the ELF binary given in argument, save it in libabigail's XML
format in a temporary file; read the ABI from the temporary XML file and compare
the ABI that has been read back against the ABI of the ELF binary given in
argument. The ABIs should compare equal. If they don't, the program emits a
diagnostic and exits with a non-zero code.
This is a debugging and sanity check option.
• --stats
Emit statistics about various internal things.
• --verbose
Emit verbose logs about the progress of miscellaneous internal things.
Notes
Alternate debug info files
As of the version 4 of the DWARF specification, Alternate debug information is a GNU
extension to the DWARF specification. It has however been proposed for inclusion into the
upcoming version 5 of the DWARF standard. You can read more about the GNU extensions to
the DWARF standard here.
abilint
abilint parses the native XML representation of an ABI as emitted by abidw. Once it has
parsed the XML representation of the ABI, abilint builds and in-memory model from it. It
then tries to save it back to an XML form, to standard output. If that read-write
operation succeeds chances are the input XML ABI representation is meaningful.
Note that the main intent of this tool to help debugging issues in the underlying
Libabigail library.
Note also that abilint can also read an ELF input file, build the in-memory model for its
ABI, and serialize that model back into XML to standard output. In that case, the ELF
input file must be accompanied with its debug information in the DWARF format.
Invocation
abilint [options] [<abi-file1>]
Options
• --help
Display a short help message and exits.
• --version | -v
Display the version of the program and exit.
• --debug-info-dir <path>
When reading an ELF input file which debug information is split out into a separate
file, this options tells abilint where to find that separate debug information file.
Note that path must point to the root directory under which the debug information is
arranged in a tree-like manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
Note also that this option is not mandatory for split debug information installed by
your system's package manager because then abidiff knows where to find it.
• --diff
For XML inputs, perform a text diff between the input and the memory model saved back
to disk. This can help to spot issues in the handling of the XML format by the
underlying Libabigail library.
• --noout
Do not display anything on standard output. The return code of the command is the
only way to know if the command succeeded.
• --stdin | --
Read the input content from standard input.
• --tu
Expect the input XML to represent a single translation unit.
CONCEPTS
ABI artifacts
An ABI artifact is a relevant part of the ABI of a shared library or program. Examples of
ABI artifacts are exported types, variables, functions, or ELF symbols exported by a
shared library.
Harmful changes
A change in the diff report is considered harmful if it might cause ABI compatibility
issues. That is, it might prevent an application dynamically linked against a given
version of a library to keep working with the changed subsequent versions of the same
library.
Harmless changes
A change in the diff report is considered harmless if it will not cause any ABI
compatibility issue. That is, it will not prevent an application dynamically linked
against given version of a library to keep working with the changed subsequent versions of
the same library.
By default, abidiff filters harmless changes from the diff report.
Suppression specifications
Definition
A suppression specification file is a way for a user to instruct abidiff to avoid emitting
reports for changes involving certain ABI artifacts.
It contains directives (or specifications) that describe the set of ABI artifacts to avoid
emitting change reports about.
Introductory examples
Its syntax is based on a simplified and customized form of Ini File Syntax. For instance,
to specify that change reports on a type named FooPrivateType should be suppressed, one
could write this suppression specification:
[suppress_type]
name = FooPrivateType
If we want to ensure that only change reports about structures named FooPrivateType should
be suppressed, we could write:
[suppress_type]
type_kind = struct
name = FooPrivateType
But we could also want to suppress change reports avoid typedefs named FooPrivateType. In
that case we would write:
[suppress_type]
type_kind = typedef
name = FooPrivateType
Or, we could want to suppress change reports about all struct which names end with the
string "PrivateType":
[suppress_type]
type_kind = struct
name_regexp = ^.*PrivateType
Let's now look at the generic syntax of suppression specification files.
Syntax
Properties
More generally, the format of suppression lists is organized around the concept of
property. Every property has a name and a value, delimited by the = sign. E.g:
name = value
Leading and trailing white spaces are ignored around property names and values.
Regular expressions
The value of some properties might be a regular expression. In that case, they must
comply with the syntax of extended POSIX regular expressions. Note that Libabigail uses
the regular expression engine of the GNU C Library.
Escaping a character in a regular expression
When trying to match a string that contains a * character, like in the pointer type int*,
one must be careful to notice that the character * is a special character in the extended
POSIX regular expression syntax. And that character must be escaped for the regular
expression engine. Thus the regular expression that would match the string int* in a
suppression file should be
int\\*
Wait; but then why the two \ characters? Well, because the \ character is a special
character in the Ini File Syntax used for specifying suppressions. So it must be escaped
as well, so that the Ini File parser leaves a \ character intact in the data stream that
is handed to the regular expression engine. Hence the \\ targeted at the Ini File parser.
So, in short, to escape a character in a regular expression, always prefix the character
with the \\ sequence.
Sections
Properties are then grouped into arbitrarily named sections that shall not be nested. The
name of the section is on a line by itself and is surrounded by square brackets, i.e:
[section_name]
property1_name = property1_value
property2_name = property2_value
A section might or might not have properties. Sections that expect to have properties and
which are found nonetheless empty are just ignored. Properties that are not recognized by
the reader are ignored as well.
Section names
Each different section can be thought of as being a directive to suppress diff reports for
a particular kind of ABI artifact.
[suppress_type]
This directive suppresses report messages about a type change.
Note that for the [suppress_type] directive to work, at least one of the following
properties must be provided:
name, name_regexp, type_kind, source_location_not_in, source_location_not_regexp.
If none of the following properties are provided, then the [suppression_type] directive is
simply ignored.
The potential properties of this sections are listed below:
• file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a binary file which
name matches the regular expression specified as value of this property.
• soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifact that are defined in a shared library which
SONAME matches the regular expression specified as value of this property.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving types whose name matches the regular expression
specified as value of this property.
• name
Usage:
name = <a-value>
Suppresses change reports involving types whose name equals the value of this property.
• type_kind
Usage:
type_kind = class | struct | union | enum |
array | typedef | builtin
Suppresses change reports involving a certain kind of type. The kind of type to
suppress change reports for is specified by the possible values listed above:
•
class: suppress change reports for class types. Note that
even if class types don't exist for C, this value still triggers the
suppression of change reports for struct types, in C. In C++ however, it
should do what it suggests.
•
struct: suppress change reports for struct types in C or C++.
Note that the value class above is a super-set of this one.
• union: suppress change reports for union types.
• enum: suppress change reports for enum types.
• array: suppress change reports for array types.
• typedef: suppress change reports for typedef types.
• builtin: suppress change reports for built-in (or native) types. Example of
built-in types are char, int, unsigned int, etc.
• source_location_not_in
Usage:
source_location_not_in = <list-of-file-paths>
Suppresses change reports involving a type which is defined in a file which path is NOT
listed in the value list-of-file-paths. Note that the value is a comma-separated list
of file paths e.g, this property
source_location_not_in = libabigail/abg-ir.h, libabigail/abg-dwarf-reader.h
suppresses change reports about all the types that are NOT defined in header files
whose path end up with the strings libabigail/abg-ir.h or
libabigail/abg-dwarf-reader.h.
• source_location_not_regexp
Usage:
source_location_not_regexp = <regular-expression>
Suppresses change reports involving a type which is defined in a file which path does
NOT match the regular expression provided as value of the property. E.g, this property
source_location_not_regexp = libabigail/abg-.*\\.h
suppresses change reports involving all the types that are NOT defined in header files
whose path match the regular expression provided a value of the property.
• has_data_member_inserted_at
Usage:
has_data_member_inserted_at = <offset-in-bit>
Suppresses change reports involving a type which has at least one data member inserted
at an offset specified by the property value offset-in-bit. The value offset-in-bit is
either:
• an integer value, expressed in bits, which denotes the offset of the insertion
point of the data member, starting from the beginning of the relevant
structure or class.
• the keyword end which is a named constant which value equals the offset of the
end of the of the structure or class.
• the function call expression offset_of(data-member-name) where
data-member-name is the name of a given data member of the relevant structure
or class. The value of this function call expression is an integer that
represents the offset of the data member denoted by data-member-name.
• the function call expression offset_after(data-member-name) where
data-member-name is the name of a given data member of the relevant structure
or class. The value of this function call expression is an integer that
represents the offset of the point that comes right after the region occupied
by the data member denoted by data-member-name.
• has_data_member_inserted_between
Usage:
has_data_member_inserted_between = {<range-begin>, <range-end>}
Suppresses change reports involving a type which has at least one data mber inserted at
an offset that is comprised in the range between range-begin`` and range-end. Please
note that each of the lues range-begin and range-end can be of the same form as the
has_data_member_inserted_at property above.
Usage examples of this properties are:
has_data_member_inserted_between = {8, 64}
or:
has_data_member_inserted_between = {16, end}
or:
has_data_member_inserted_between = {offset_after(member1), end}
• has_data_members_inserted_between
Usage:
has_data_members_inserted_between = {<sequence-of-ranges>}
Suppresses change reports involving a type which has multiple data member inserted in
various offset ranges. A usage example of this property is, for instance:
has_data_members_inserted_between = {{8, 31}, {72, 95}}
This usage example suppresses change reports involving a type which has data members
inserted in bit offset ranges [8 31] and [72 95]. The length of the sequence of ranges
or this has_data_members_inserted_between is not bounded; it can be as long as the
system can cope with. The values of the boundaries of the ranges are of the same kind
as for the has_data_member_inserted_at property above.
Another usage example of this property is thus:
has_data_members_inserted_between =
{
{offset_after(member0), offset_of(member1)},
{72, end}
}
• accessed_through
Usage:
accessed_through = <some-predefined-values>
Suppress change reports involving a type which is referred to either directly or
through a pointer or a reference. The potential values of this property are the
predefined keywords below:
• direct
So if the [suppress_type] contains the property description:
accessed_through = direct
then changes about a type that is referred-to directly (i.e, not through a
pointer or a reference) are going to be suppressed.
• pointer
If the accessed_through property is set to the value pointer then changes about a
type that is referred-to through a pointer are going to be suppressed.
• reference
If the accessed_through property is set to the value reference then changes about
a type that is referred-to through a reference are going to be suppressed.
• reference-or-pointer
If the accessed_through property is set to the value reference-or-pointer then
changes about a type that is referred-to through either a reference or a pointer
are going to be suppressed.
For an extensive example of how to use this property, please check out the example
below about suppressing change reports about types accessed either directly or through
pointers.
• label
Usage:
label = <some-value>
Define a label for the section. A label is just an informative string that might be
used by abidiff to refer to a type suppression in error messages.
[suppress_function]
This directive suppresses report messages about changes on a set of functions.
Note that for the [suppress_function] directive to work, at least one of the following
properties must be provided:
label, name, name_regexp, parameter, return_type_name, symbol_name, symbol_name_regexp,
symbol_version, symbol_version_regexp.
If none of the following properties are provided, then the [suppression_function]
directive is simply ignored.
The potential properties of this sections are:
• label
Usage:
label = <some-value>
This property is the same as the label property defined above.
• name
Usage:
name = <some-value>
Suppresses change reports involving functions whose name equals the value of this
property.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving functions whose name matches the regular expression
specified as value of this property.
Let's consider the case of functions that have several symbol names. This happens when
the underlying symbol for the function has aliases. Each symbol name is actually one
alias name.
In this case, if the regular expression matches the name of at least one of the aliases
names, then it must match the names of all of the aliases of the function for the
directive to actually suppress the diff reports for said function.
• change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification should apply to. The
possible values of this property as well as their meaning are listed below:
• function-subtype-change
This suppression specification applies to functions that which have at least one
sub-type that has changed.
• added-function
This suppression specification applies to functions that have been added to the
binary.
• deleted-function
This suppression specification applies to functions that have been removed from
the binary.
• all
This suppression specification applies to functions that have all of the changes
above. Note that not providing the change_kind property at all is equivalent to
setting it to the value all.
• parameter
Usage:
parameter = <function-parameter-specification>
Suppresses change reports involving functions whose parameters match the parameter
specification indicated as value of this property.
The format of the function parameter specification is:
' <parameter-index> <space> <type-name-or-regular-expression>
That is, an apostrophe followed by a number that is the index of the parameter,
followed by one of several spaces, followed by either the name of the type of the
parameter, or a regular expression describing a family of parameter type names.
If the parameter type name is designated by a regular expression, then said regular
expression must be enclosed between two slashes; like /some-regular-expression/.
The index of the first parameter of the function is zero. Note that for member
functions (methods of classes), the this is the first parameter that comes after the
implicit "this" pointer parameter.
Examples of function parameter specifications are:
'0 int
Which means, the parameter at index 0, whose type name is int.
'4 unsigned char*
Which means, the parameter at index 4, whose type name is unsigned char*.
'2 /^foo.*&/
Which means, the parameter at index 2, whose type name starts with the string "foo" and
ends with an '&'. In other words, this is the third parameter and it's a reference on
a type that starts with the string "foo".
• return_type_name
Usage:
return_type_name = <some-value>
Suppresses change reports involving functions whose return type name equals the value
of this property.
• return_type_regexp
Usage:
return_type_regexp = <regular-expression>
Suppresses change reports involving functions whose return type name matches the
regular expression specified as value of this property.
• symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving functions whose symbol name equals the value of
this property.
• symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol name matches the regular
expression specified as value of this property.
Let's consider the case of functions that have several symbol names. This happens when
the underlying symbol for the function has aliases. Each symbol name is actually one
alias name.
In this case, the regular expression must match the names of all of the aliases of the
function for the directive to actually suppress the diff reports for said function.
• symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving functions whose symbol version equals the value of
this property.
• symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol version matches the regular
expression specified as value of this property.
[suppress_variable]
This directive suppresses report messages about changes on a set of variables.
Note that for the [suppress_variable] directive to work, at least one of the following
properties must be provided:
label, name, name_regexp, symbol_name, symbol_name_regexp, symbol_version,
symbol_version_regexp.
If none of the following properties are provided, then the [suppres_variable] directive is
simply ignored.
The potential properties of this sections are:
• label
Usage:
label = <some-value>
This property is the same as the label property defined above.
• name
Usage:
name = <some-value>
Suppresses change reports involving variables whose name equals the value of this
property.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving variables whose name matches the regular expression
specified as value of this property.
• change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification should apply to. The
possible values of this property as well as their meaning are the same as when it's
used in the [suppress_function] section.
• symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving variables whose symbol name equals the value of
this property.
• symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol name matches the regular
expression specified as value of this property.
• symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving variables whose symbol version equals the value of
this property.
• symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol version matches the regular
expression specified as value of this property.
• type_name
Usage:
type_name = <some-value>
Suppresses change reports involving variables whose type name equals the value of this
property.
• type_name_regexp
Usage:
type_name_regexp = <regular-expression>
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 abidiff 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.
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)
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.
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 regular expressions:
$ 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
$
AUTHOR
Dodji Seketeli
COPYRIGHT
2014, Red Hat, Inc.
March 10, 2016 LIBABIGAIL(7)