NAME

abipkgdiff - compare ABIs of ELF files in software packages
 
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 either in DWARF or in CTF formats. Please note however that some packages contain binaries that embed the debug information directly in a section of said binaries. In those cases, obviously, no separate debug information package is needed as the tool will find the debug information inside the binaries.
 
By default, abipkgdiff uses debug information in DWARF format, if present, otherwise it compares binaries interfaces using debug information in CTF format, if present, finally, if neither is found, it uses only ELF symbols to report which of them were added or removed.
 
This tool uses the libabigail library to analyze the binary as well as its associated debug information. Here is its general mode of operation.
 
When instructed to do so, a binary and its associated debug information is read and analyzed. To that effect, libabigail analyzes by default the descriptions of the types reachable by the interfaces (functions and variables) that are visible outside of their translation unit. Once that analysis is done, an Application Binary Interface Corpus is constructed by only considering the subset of types reachable from interfaces associated to ELF symbols that are defined and exported by the binary. It’s that final ABI corpus which libabigail considers as representing the ABI of the analyzed binary.
 
Libabigail then has capabilities to generate textual representations of ABI Corpora, compare them, analyze their changes and report about them.

INVOCATION

 
abipkgdiff [option] <package1> <package2>


 
package1 and package2 are the packages that contain the binaries to be compared.

ENVIRONMENT

abipkgdiff loads two default suppression specifications files, merges their content and use it to filter out ABI change reports that might be considered as false positives to users.
•
Default system-wide suppression specification file It’s located by the optional environment variable LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that environment variable is not set, then abipkgdiff tries to load the suppression file $libdir/libabigail/libabigail-default.abignore. If that file is not present, then no default system-wide suppression specification file is loaded.
•
Default user suppression specification file. It’s located by the optional environment LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment variable is not set, then abipkgdiff tries to load the suppression file $HOME/.abignore. If that file is not present, then no default user suppression specification is loaded.

 
In addition to those default suppression specification files, abipkgdiff will also look inside the packages being compared and if it sees a file that ends with the extension .abignore, then it will consider it as a suppression specification and it will combine it to the default suppression specification that might be already loaded.
 
The user might as well use the --suppressions option (that is documented further below) to provide a suppression specification.

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. Note that the debug info for package1 can have been split into several different debug info packages. In that case, several instances of this options can be provided, along with those several different debug info packages.
•
--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. Note that the debug info for package2 can have been split into several different debug info packages. In that case, several instances of this options can be provided, along with those several different debug info packages.
•
--devel-pkg1 | --devel1 <path> Specifies where to find the Development Package associated with the first package to be compared. That Development Package at path should at least contain header files in which public types exposed by the libraries (of the first package to be compared) are defined. When this option is provided, the tool filters out reports about ABI changes to types that are NOT defined in these header files.
•
--devel-pkg2 | --devel2 <path> Specifies where to find the Development Package associated with the second package to be compared. That Development Package at path should at least contains header files in which public types exposed by the libraries (of the second package to be compared) are defined. When this option is provided, the tool filters out reports about ABI changes to types that are NOT defined in these header files.
•
--drop-private-types This option is to be used with the --devel-pkg1 and --devel-pkg2 options. With this option, types that are NOT defined in the headers are entirely dropped from the internal representation build by Libabigail to represent the ABI. They thus don’t have to be filtered out from the final ABI change report because they are not even present in Libabigail’s representation. Without this option however, those private types are kept in the internal representation and later filtered out from the report. This options thus potentially makes Libabigail consume less memory. It’s meant to be mainly used to optimize the memory consumption of the tool on binaries with a lot of publicly defined and exported types.
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--dso-only Compare ELF files that are shared libraries, only. Do not compare executable files, for instance.
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--private-dso By default, abipkgdiff does not compare DSOs that are private to the RPM package. A private DSO is a DSO which SONAME is NOT advertised in the “provides” property of the RPM. This option instructs abipkgdiff to also compare DSOs that are NOT advertised in the “provides” property of the RPM. Please note that the fact that (by default) abipkgdiff skips private DSO is a feature that is available only for RPMs, at the moment. We would happily accept patches adding that feature for other package formats.
•
--leaf-changes-only|-l only show leaf changes, so don’t show impact analysis report. This option implies --redundant The typical output of abipkgdiff and abidiff when comparing two binaries, that we shall call full impact report, looks like this
 
$ 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 fn(C&)' at test-v1.cc:13:1 has some indirect sub-type changes:
    parameter 1 of type 'C&' has sub-type changes:
      in referenced type 'struct C' at test-v1.cc:7:1:
        type size hasn't changed
        1 data member change:
         type of 'leaf* C::m0' changed:
           in pointed to type 'struct leaf' at test-v1.cc:1:1:
             type size changed from 32 to 64 bits
             1 data member insertion:
               'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1


$


 
So in that example the report emits information about how the data member insertion change of “struct leaf” is reachable from function “void fn(C&)”. In other words, the report not only shows the data member change on “struct leaf”, but it also shows the impact of that change on the function “void fn(C&)”.
 
In abidiff (and abipkgdiff) parlance, the change on “struct leaf” is called a leaf change. So the --leaf-changes-only --impacted-interfaces options show, well, only the leaf change. And it goes like this:
 
$ abidiff -l libtest-v0.so libtest-v1.so
'struct leaf' changed:
  type size changed from 32 to 64 bits
  1 data member insertion:
    'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1


  one impacted interface:
    function void fn(C&)
$


 
Note how the report ends up by showing the list of interfaces impacted by the leaf change. That’s the effect of the additional --impacted-interfaces option.
 
Now if you don’t want to see that list of impacted interfaces, then you can just avoid using the --impacted-interface option. You can learn about that option below, in any case.
 
Please note that when comparing two Linux Kernel packages, it’s this leaf changes report that is emitted, by default. The normal so-called full impact report can be emitted with the option --full-impact which is documented later below.
•
--impacted-interfaces When showing leaf changes, this option instructs abipkgdiff to show the list of impacted interfaces. This option is thus to be used in addition to the --leaf-changes-only option, or, when comparing two Linux Kernel packages. Otherwise, it’s simply ignored.
•
--full-impact|-f When comparing two Linux Kernel packages, this function instructs abipkgdiff to emit the so-called full impact report, which is the default report kind emitted by the abidiff tool:
 
$ 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 fn(C&)' at test-v1.cc:13:1 has some indirect sub-type changes:
    parameter 1 of type 'C&' has sub-type changes:
      in referenced type 'struct C' at test-v1.cc:7:1:
        type size hasn't changed
        1 data member change:
         type of 'leaf* C::m0' changed:
           in pointed to type 'struct leaf' at test-v1.cc:1:1:
             type size changed from 32 to 64 bits
             1 data member insertion:
               'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1


$


•
--non-reachable-types|-t Analyze and emit change reports for all the types of the binary, including those that are not reachable from global functions and variables. This option might incur some serious performance degradation as the number of types analyzed can be huge. However, if paired with the --devel-pkg{1,2} options, the additional non-reachable types analyzed are restricted to those defined in the public headers files carried by the referenced development packages, thus hopefully making the performance hit acceptable. Also, using this option alongside suppression specifications (by also using the --suppressions option) might help keep the number of analyzed types (and the potential performance degradation) in control. Note that without this option, only types that are reachable from global functions and variables are analyzed, so the tool detects and reports changes on these reachable types only.
•
--exported-interfaces-only By default, when looking at the debug information accompanying a binary, this tool analyzes the descriptions of the types reachable by the interfaces (functions and variables) that are visible outside of their translation unit. Once that analysis is done, an ABI corpus is constructed by only considering the subset of types reachable from interfaces associated to ELF symbols that are defined and exported by the binary. It’s those final ABI Corpora that are compared by this tool. The problem with that approach however is that analyzing all the interfaces that are visible from outside their translation unit can amount to a lot of data, especially when those binaries are applications, as opposed to shared libraries. One example of such applications is the 
`Linux Kernel`_
. Analyzing massive ABI corpora like these can be extremely slow. To mitigate that performance issue, this option allows libabigail to only analyze types that are reachable from interfaces associated with defined and exported ELF symbols. Note that this option is turned on by default when analyzing the 
`Linux Kernel`_
. Otherwise, it’s turned off by default.
•
--allow-non-exported-interfaces When looking at the debug information accompanying a binary, this tool analyzes the descriptions of the types reachable by the interfaces (functions and variables) that are visible outside of their translation unit. Once that analysis is done, an ABI corpus is constructed by only considering the subset of types reachable from interfaces associated to ELF symbols that are defined and exported by the binary. It’s those final ABI Corpora that are compared by this tool. The problem with that approach however is that analyzing all the interfaces that are visible from outside their translation unit can amount to a lot of data, especially when those binaries are applications, as opposed to shared libraries. One example of such applications is the 
`Linux Kernel`_
. Analyzing massive ABI Corpora like these can be extremely slow. In the presence of an “average sized” binary however one can afford having libabigail analyze all interfaces that are visible outside of their translation unit, using this option. Note that this option is turned on by default, unless we are in the presence of the 
`Linux Kernel`_
.
•
--redundant

In the diff reports, do display redundant changes. A redundant change is a change that has been displayed elsewhere in a given 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 chance to spot real ABI issues.
•
--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 package for the presence of suppression files.
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--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.
•
--no-default-suppression Do not load the default suppression specification files.
•
--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. In that case, all of the suppression specification files are taken into account. Please note that, by default, if this option is not provided, then the default suppression specification files are loaded .
•
--linux-kernel-abi-whitelist | -w <path-to-whitelist> When comparing two Linux kernel RPM packages, this option points to the white list of names of ELF symbols of functions and variables that must be compared for ABI changes. That white list is called a “Linux kernel ABI white list”. Any other function or variable which ELF symbol are not present in that white list will not be considered by the ABI comparison process. If this option is not provided – thus if no white list is provided – then the ABI of all publicly defined and exported functions and global variables by the Linux Kernel binaries are compared. Please note that if a white list package is given in parameter, this option handles it just fine, like if the –wp option was used.
•
--wp <path-to-whitelist-package> When comparing two Linux kernel RPM packages, this option points an RPM package containining several white lists of names of ELF symbols of functions and variables that must be compared for ABI changes. Those white lists are called “Linux kernel ABI white lists”. From the content of that white list package, this program then chooses the appropriate Linux kernel ABI white list to consider when comparing the ABI of Linux kernel binaries contained in the Linux kernel packages provided on the command line. That choosen Linux kernel ABI white list contains the list of names of ELF symbols of functions and variables that must be compared for ABI changes. Any other function or variable which ELF symbol are not present in that white list will not be considered by the ABI comparison process. Note that this option can be provided twice (not mor than twice), specifying one white list package for each Linux Kernel package that is provided on the command line. If this option is not provided – thus if no white list is provided – then the ABI of all publicly defined and exported functions and global variables by the Linux Kernel binaries are compared.
•
--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.
•
--no-show-locs

Do not show information about where in the second shared library the respective type was changed.


•
--show-bytes Show sizes and offsets in bytes, not bits. By default, sizes and offsets are shown in bits.
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--show-bits Show sizes and offsets in bits, not bytes. This option is activated by default.
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--show-hex Show sizes and offsets in hexadecimal base.
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--show-dec Show sizes and offsets in decimal base. This option is activated by default.
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--no-show-relative-offset-changes Without this option, when the offset of a data member changes, the change report not only mentions the older and newer offset, but it also mentions by how many bits the data member changes. With this option, the latter is not shown.
•
--show-identical-binaries

Show the names of the all binaries compared, including the binaries whose ABI compare equal. By default, when this option is not provided, only binaries with ABI changes are mentionned in the output.


•
--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.
•
--self-check This is used to test the underlying Libabigail library. When in used, the command expects only on input package, along with its associated debug info packages. The command then compares each binary inside the package against its own ABIXML representation. The result of the comparison should yield the empty set if Libabigail behaves correctly. Otherwise, it means there is an issue that ought to be fixed. This option is used by people interested in Libabigail development for regression testing purposes. Here is an example of the use of this option:
 
$ abipkgdiff --self-check --d1 mesa-libGLU-debuginfo-9.0.1-3.fc33.x86_64.rpm  mesa-libGLU-9.0.1-3.fc33.x86_64.rpm
 ==== SELF CHECK SUCCEEDED for 'libGLU.so.1.3.1' ====
$


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--no-assume-odr-for-cplusplus When analysing a binary originating from C++ code using DWARF debug information, libabigail assumes the One Definition Rule to speed-up the analysis. In that case, when several types have the same name in the binary, they are assumed to all be equal. This option disables that assumption and instructs libabigail to actually actually compare the types to determine if they are equal.
•
--no-leverage-dwarf-factorization When analysing a binary which DWARF debug information was processed with the DWZ tool, the type information is supposed to be already factorized. That context is used by libabigail to perform some speed optimizations. This option disables those optimizations.
•
--ctf
This is used to compare packages with CTF debug information, if present.





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.

AUTHOR

Dodji Seketeli 2014-2023, Red Hat, Inc.