Source: python3.13 Severity: wishlist X-Debbugs-Cc: reproducible-b...@lists.alioth.debian.org User: reproducible-bui...@lists.alioth.debian.org Usertags: randomness
Dear Maintainer, I'm an occasional volunteer contributor to the Reproducible Builds[1] project, and noticed recently that python3.13 fails to build reproducibly according to automated reproducibility testing[2] on Debian. If I understand correctly, the packaging for src:python3.13 enables link-time optimization (LTO) with fat link-time objects enabled (the -ffat-lto-objects flag to GCC). According to GCC bugreport[3] 66305, enabling this flag causes nondeterministic output; and the bugthread also provides a potential workaround/resolution for that, namely to enable the -frandom-seed GCC option[4]. Another detail from the thread is that GCC8 introduced a bug that meant that the random seed value of zero caused the option to be ignored. I would like to request that we enable the random-seed GCC option of one (1), in order to enable deterministic (reproducible) link-time optimized object files during the build of python3.13-related packages. I _think_ the relevant line of code to adjust in the buildscript is found at: https://salsa.debian.org/cpython-team/python3/-/blob/f04d169fe2dc39d34b7f983b17ae6a5190714cb6/debian/rules#L235 ...however I also note that a subsequent line in the script may also require an update, to consistently filter out LTO-related flags: https://salsa.debian.org/cpython-team/python3/-/blob/f04d169fe2dc39d34b7f983b17ae6a5190714cb6/debian/rules#L244 I hope (but cannot guarantee) to find time to test this theory using a triplicate set of builds; once without the adjustment applied (producing what I expect to be a somewhat-random build output), then with two subsequent builds with the random-seed enabled (to confirm whether those two additional builds emit identical binary packages). Regards, James [1] - https://reproducible-builds.org/ [2] - https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/python3.13.html [3] - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66305 [4] - https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html#index-frandom-seed
