Currently libspl is a static archive that is linked into multiple shared
objects, which then re-export its symbols. We intend to fix this soon.
For the moment though, most programs shipped with OpenZFS depend on two
or more of these shared objects, and see the same symbols twice. For
functions this is not a problem, as they do not have any mutable state
and so the linker can simply select the first one and use that for all.
For global data objects however, each shared object will have direct
(non-relocatable) references to its own instance of the symbol, such
that changes on one will not necessarily be seen by the other. While
this shouldn't be a problem in practice as these reexported interfaces
are not supposed to be used, they are technically undefined behaviour in
C (C17 6.9.2) and are reported by ASAN as a violation of C++'s "One
Definition Rule".
To fix this, we hide these globals inside their compilation units, and
add access functions and macros as appropriate to preserve the existing
API (though not ABI).
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes#17861
4d451bae8a