HI Martin, Thanks very much for the suggestions as well as all the information about the qsort issues.
Did you ever publish your changes as a patch, or create a write up about what was necessary to create a reproducible build? I would be interested to see what others have done, and potentially anything else I may have missed. Thanks /Cole On 21 December 2015 at 21:08, Martin Sebor <mse...@gmail.com> wrote: > On 12/20/2015 11:39 PM, Cole wrote: >> >> Hi, >> >> I am busy trying to generate a package for gcc that is consistent >> between two successive builds, and I am now down to the final few >> files. >> >> I am stuck with the file: cilk-abi-cilk-for.o, which is obviously >> built with -O2, but between two successive builds, the assembly code >> generated is different. Please refer to [1] for output and details. >> >> Would anyone have any suggestions that I might be able to try to get >> the file to generate the same assembly code? > > > It's been some time since I had to deal with this problem and > my recollection is somewhat fuzzy and probably inaccurate. IIRC, > part of it was caused by qsort being unstable (I think that was > on Solaris). We replaced it with a stable version. Another part > of it might have been caused by changes in the address space > layout caused by ASLR (causing differences in hash values used > by the register allocator or something like that). We disabled > ASLR to get around that (and other problems). With that, we had > fully repeatable builds. This was in the GCC 4.5 time frame. > With newer versions, there's also LTO that can affect things. > The -frandom-seed= option exists to make it possible to emit > identical object files that might otherwise be different. > > Martin >
