[Bug 2071468] Re: ELF package metadata failure: environment variable ‘DEB_HOST_ARCH’ not defined

[Matthias Klose]

just curious: are there any pointers to these discussions?  It seems odd
to design a format that has quoting issues from the beginning.

I don't like having a 99% solution, and skip stuff otherwise. Plus it's
not just problematic for regular package builds, but also for debugging
a package build.  You have to set all these environment variables on
your own, when you restart some part of a package build.

I see two ways to get around that:

 - a package build creates a build specific spec without relying on any
environment variables. That would be a change in dpkg, plus passing the
--package-metadata in the build flags.

 - the gcc and clang drivers insert the --package-metadata option on
it's own, if it is not present, and if all the env vars are present.
This would not need *any* changes in dpkg, just a simple local patch to
the compiler drivers. In case of not having the env vars, it just would
not be recorded, but not failing the build as it's currently the case.

Both options seem to be better than the current status.

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https://bugs.launchpad.net/bugs/2071468

Title:
  ELF package metadata failure: environment variable ‘DEB_HOST_ARCH’ not
  defined

Status in dpkg package in Ubuntu:
  New

Bug description:
  The ELF package note metadata introduced in dpkg 1.22.6ubuntu11
  (refined in 1.22.6ubuntu14) can cause this failure:

  ```
  gcc fatal error: environment variable ‘DEB_HOST_ARCH’ not defined
  ```

  This happens when the `-specs=/usr/share/dpkg/elf-package-
  metadata.specs` parameter is set but the needed environment variables
  are not set. Cases:

  1. Only the LDFLAGS is queried from dpkg-buildflags. Affected source
  packages builds: python3.12, openjdk-21, cdbs (causing dvbstreamer and
  rp-pppoe fail to build)

  2. autopkgtests

  This approach is too fragile. An alternative approach would be to specify the `--package-metadata` linker flag directly. The problem with that approach is that the curly brackets and quotation marks need to be escaped. Example failure: Building dpkg would add this parameter to the LDFLAGS:
  ```
  -Wl,--package-metadata,{"type":"deb","os":"ubuntu","name":"dpkg","version":"1.22.6ubuntu15","architecture":"amd64"}
  ```
  The following configure script call (non-relevant parameters deleted):
  ```
  $ gcc -Wl,--package-metadata,{type:deb,os:ubuntu,name:dpkg,version:1.22.6ubuntu15,architecture:amd64}
  /usr/bin/ld: cannot find {type:deb: No such file or directory
  /usr/bin/ld: cannot find os:ubuntu: No such file or directory
  /usr/bin/ld: cannot find name:dpkg: No such file or directory
  /usr/bin/ld: cannot find version:1.22.6ubuntu15: No such file or directory
  /usr/bin/ld: cannot find architecture:amd64}: No such file or directory
  ```

  Proposed solution: Add support for an `--escaped-package-metadata` parameter to the linkers that takes an URL encoded (RFC 3986) parameter. Example:
  ```
  -Wl,--encoded-package-metadata,%7B%22type%22:%22deb%22%2C%22os%22:%22ubuntu%22%2C%22name%22:%22dpkg%22%2C%22version%22:%221.22.6ubuntu15%22%2C%22architecture%22:%22amd64%22%7D
  ```

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