сравнить ABI файлов ELF (compare ABIs of ELF files)
Возвращаемое значение (Return value)
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.
Note that, at the moment, there are only a few kinds of ABI
changes that would result in setting the flag
ABIDIFF_ABI_INCOMPATIBLE_CHANGE. Those ABI changes are either:
• the removal of the symbol of a function or variable that has
been defined and exported.
• the modification of the index of a member of a virtual
function table (for C++ programs and libraries).
With time, when more ABI change patterns are found to always
constitute incompatible ABI changes, we will adapt the code to
recognize those cases and set the ABIDIFF_ABI_INCOMPATIBLE_CHANGE
accordingly. So, if you find such patterns, please let us know.
The remaining bits are not used for the moment.
