[Bug 2082636] Re: [SRU] dpkg: backport frame-pointer enabling mechanism for Rust

[Timo Aaltonen]

Hello Zixing, or anyone else affected,

Accepted dpkg into noble-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/dpkg/1.22.6ubuntu6.2
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
noble to verification-done-noble. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-noble. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: dpkg (Ubuntu Noble)
       Status: New => Fix Committed

** Tags added: verification-needed verification-needed-noble

** Changed in: dpkg (Ubuntu)
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/2082636

Title:
  [SRU] dpkg: backport frame-pointer enabling mechanism for Rust

Status in dpkg package in Ubuntu:
  Fix Released
Status in dpkg source package in Noble:
  Fix Committed

Bug description:
  [ Impact ]

   * On Noble, dpkg scripts could not produce Rust binaries with frame-
  pointer enabled.

  [ Test Plan ]

   * Build a Rust binary package like ripgrep and you will not find frame-pointers being used in the binary.
   * Since LLVM could inline and choose to optimize frame pointers away in some cases, you will need to check the disassembly of the program around the function prologue to see if the frame pointer register is correctly saved to stack (rbp/ebp on x86 architecture). You can use the script provided in https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/2082636/+attachment/5840384/+files/check-rust-fp.py to check if the frame pointers have been enabled.

  [ Where problems could occur ]

   * On older Rust versions (Rust <= 1.80), it is known that LLVM on s390x sometimes can produce incorrect warnings about how the "backchain" feature does not exist.
   * On older LLVM versions (LLVM <= 17), LLVM may not produce correct backchain saving logic inside the function prologue.

  [ Other Info ]

   * This change is mandatory to enable Rust-related packages with
  frame-pointers during the build.

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