rustup binaries vary from readdir order

[bmwiedemann]

Problem

While working on reproducible builds for openSUSE, I found that
our rustup package varies from non-deterministic filesystem readdir order that influences the rustup binary machine code.

In the build system I can see variations in
liblzma_sys ...rlib
libzstd_sys ...rlib
rustup_init

Steps

1. use disorderfs --shuffle-dirents=yes or a scratch ext4 filesystem to build rustup twice

Possible Solution(s)

need to sort relevant source or .o file lists

Notes

/usr/bin/rustup differs in assembler output
--- old /usr/bin/rustup (disasm)
+++ new /usr/bin/rustup (disasm)
@@ -1068357,1696 +1068357,126 @@
        jmp    <ZSTD_decompressStream + ofs>
        xchg   %ax,%ax

-ZSTDv07_defaultAllocFunction:
-       mov    %rsi,%rdi
-       jmp    <malloc@plt>
-       nopl   offset(%rax,%rax,1)
-...
+FSEv05_buildDTable:

Rustup version

rustup-1.24.3~0.tar.xz

Installed toolchains

openSUSE Tumbleweed 20220330
rust-1.59.0

[kinnison]

This is very likely out of our control - that looks like it's code which is differing, and that'd be up to the compiler not us. You should try and discuss this with the rust-lang/rust people.

[kinnison]

If, after discussion with them, they believe it's the fault of something in rustup then please reopen this issue.

[bmwiedemann]

Meanwhile I found gyscos/zstd-rs#162 helps and
liblzma_sys.rlib needs a similar fix.
So probably not a rust-lang issue.