setup-build-env: Fix cross-compilation dependencies - #230
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theihor
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August 11, 2026 20:02
theihor
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Cross-compilation is broken for every Debian target. glibc 2.43-3 entered
unstable on 2026-08-10, and libc6-dev:<arch> from 2.43 onwards declares
Breaks: libc6-dev-<arch>-cross (<< 2.43~)
while src:cross-toolchain-base is still at version 80 and ships
libc6-dev-<arch>-cross 2.42-12cross1. g++-<ver>-<arch>-linux-gnu depends on it
through libstdc++-<ver>-dev-<arch>-cross, so installing the cross toolchain and
the multiarch :<arch> -dev libraries in a single apt transaction is now
unsatisfiable. Waiting for the archive is not an option: cross-toolchain-base
cannot be rebuilt at all until its Build-Depends stop naming linux-source-6.18,
which sid left behind long ago (Debian #1130544, open since 2026-03-12; the
glibc skew itself is #1144098).
The root problem is that the target libraries are installed into the host dpkg
database. That subjects them to Multi-Arch: same version equality against the
host-arch copies, and to the Breaks above, neither of which has anything to do
with cross-compiling. Version skew between the builder image and the archive is
already fatal for a second, independent reason: the image carries libssl-dev
3.6.2-1 while the archive offers 3.6.3-1.
Download the target libraries and unpack them into the cross toolchain's own
triplet directory instead. apt-get download resolves no dependencies and writes
no dpkg state, so neither constraint can apply, and /usr/<arch>-linux-gnu is
already on the cross gcc's default search path, so no build flags change.
Drop linux-libc-dev:<arch>: it is Architecture: all, so the qualifier was a
no-op, and the target UAPI headers come from linux-libc-dev-<arch>-cross.
Verified on Debian sid with gcc-15, Ubuntu noble with gcc-14 and Ubuntu plucky
with gcc-15, building libbpf, a static cross bpftool, sign-file, and clang's
s390x userspace targets.
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
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Cross-compilation is broken for every Debian target. glibc 2.43-3 entered unstable on 2026-08-10, and libc6-dev: from 2.43 onwards declares
while src:cross-toolchain-base is still at version 80 and ships libc6-dev--cross 2.42-12cross1. g++---linux-gnu depends on it through libstdc++--dev--cross, so installing the cross toolchain and the multiarch : -dev libraries in a single apt transaction is now unsatisfiable. Waiting for the archive is not an option: cross-toolchain-base cannot be rebuilt at all until its Build-Depends stop naming linux-source-6.18, which sid left behind long ago (Debian #1130544, open since 2026-03-12; the glibc skew itself is #1144098).
The root problem is that the target libraries are installed into the host dpkg database. That subjects them to Multi-Arch: same version equality against the host-arch copies, and to the Breaks above, neither of which has anything to do with cross-compiling. Version skew between the builder image and the archive is already fatal for a second, independent reason: the image carries libssl-dev 3.6.2-1 while the archive offers 3.6.3-1.
Download the target libraries and unpack them into the cross toolchain's own triplet directory instead. apt-get download resolves no dependencies and writes no dpkg state, so neither constraint can apply, and /usr/-linux-gnu is already on the cross gcc's default search path, so no build flags change.
Drop linux-libc-dev:: it is Architecture: all, so the qualifier was a no-op, and the target UAPI headers come from linux-libc-dev--cross.
Verified on Debian sid with gcc-15, Ubuntu noble with gcc-14 and Ubuntu plucky with gcc-15, building libbpf, a static cross bpftool, sign-file, and clang's s390x userspace targets.