ExtUtils::ParseXS generates nondeterministic C files (differing order) out of .xs files. This leads to differently compiled objects. . There are some code copies, so we have the following bugs in total- https://bugs.debian.org/829295 https://bugs.debian.org/829296 . Fix is also required in ExtUtils::ParseXS in perl(-modules)
ExtUtils::XSPP generates random identifiers that are included in generated C code. https://sources.debian.net/src/libextutils-xspp-perl/latest/lib/ExtUtils/XSpp/Lexer.pm/#L141 . Possible solution is seeding the rng with srand($SOURCE_DATE_EPOCH) in ExtUtils/XSpp/Cmd.pm.
Our notes about issues affecting packages are stored in notes.git and are targeted at packages in Debian in 'unstable/amd64' (unless they say otherwise).