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PROGRAM:

NAME

abidiff - compare ABIs of ELF files

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}

$

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