On September 30, 2025 1:06:24 PM GMT+02:00, Helmut Grohne <[email protected]>
wrote:
>Package: dh-rust
>Version: 0.0.11
>Severity: important
>Justification: breaks cross building of several packages
>Control: affects -1 + src:btm src:precious src:resvg
>User: [email protected]
>Usertags: ftcbfs
>X-Debbugs-Cc: [email protected], [email protected]
>Control: block 1112299 by -1
>
>Hi Jonas and Fabian,
>
>earlier, I reported a cross build failure #1112299 in resvg and observed
>that it was using the build architecture compiler as linker. I now
>recognize this as a pattern also affecting btm and precious and probably
>more. A common pattern is that they all use dh-rust. I checked a number
>of dh-rust using packages and found none that would actually cross
>build. The vast majority is bd-uninstallable due to some toolchain
>conflict (e.g. librust-tree-sitter-dev depending on rustc is bad or llvm
>finally dropped their incorrect m-a:same annotations). The few where a
>build is attempted either fail to understand the triplet passed to
>-target (often a sign for missing libstd-rust-dev) or fail when they
>link with the wrong C compiler.
>
>I still do not understand why this is happening. This is what I wrote in
>the earlier #1112299 bug report:
>
>> Next up, it uses the build architecture compiler for linking the resvg
>> executable. I spent some time trying to understand why an asked Fabian
>> for help, but I wasn't able to figure out the root cause. I confirm,
>> that dh-rust correctly inserts -C linker=... into the config.toml in
>> section [target.'cfg(all())'], but the actual linker invocation lacks
>> both the supplied linker and link-arg. I note that dh-cargo uses a
>> different section [build], but changing the section to match dh-cargo's
>> does not fix the problem. Would someone else see what the problem is
>> here?
The problem is bigger than just cross building being broken:
dh-rust sets RUSTFLAGS in the environment.
that takes precedence over anything in the config:
https://doc.rust-lang.org/cargo/reference/config.html#buildrustflags
not only the linker and its flags, but also debugging symbols
(both generating them and the remap prefix) are broken as a result.
>Would someone have suggestions on how to debug this? You should be able
>to reproduce this as simple as "sbuild -d unstable --host riscv64
>$somepackage" using one of the affected ones.
>
>Helmut
>
