Bug#1140150: libpoco-dev: not co-installable across architectures in trixie (Multi-Arch: same dropped in 1.13.0-6)

Package: libpoco-dev
Version: 1.13.0-6+b2
Severity: normal

Dear Maintainer,

In a clean debian:trixie environment with a foreign architecture enabled,
libpoco-dev:amd64 and libpoco-dev:arm64 cannot be installed simultaneously:

# docker run --rm debian:trixie bash
dpkg --add-architecture arm64
apt-get update
apt-get install -s libpoco-dev:amd64 libpoco-dev:arm64
...
libpoco-dev : Conflicts: libpoco-dev:arm64 but 1.13.0-6+b2 is to be
installed
libpoco-dev:arm64 : Conflicts: libpoco-dev but 1.13.0-6+b2 is to be
installed

Root cause: the libpoco-dev binary package in trixie (1.13.0-6+b2) is not
marked "Multi-Arch: same". The field was deliberately removed in 1.13.0-6
("Disclaim libpoco-dev to be MA same", closing my earlier bug #1064971).
Closing #1064971 by dropping Multi-Arch instead of resolving the underlying
file layout means the -dev package is, by design, no longer co-installable
across architectures -- which is a regression for cross-arch development.

The good news: this has effectively already been corrected in unstable.
libpoco-dev 1.14.2-6 (sid) restores "Multi-Arch: same", and I have verified
it is genuinely co-installable: all 855 shared headers under /usr/include
are byte-identical between amd64 and arm64, and every architecture-specific
.so development symlink lives in its triplet path (/usr/lib/<triplet>/), so
there are no shared-path file conflicts.

Request: please restore "Multi-Arch: same" for libpoco-dev in trixie via a
stable update (it is a one-line debian/control change, already present in
1.14.2-6). I'm happy to prepare the debdiff / NMU if that helps, given the
package is currently QA-maintained.

Note on a second, independent blocker (not libpoco-dev's bug, flagged here
for completeness): even with Multi-Arch: same restored, co-installing the
two libpoco-dev arches is still blocked by the dependency on
default-libmysqlclient-dev, whose libmariadb-dev-compat is not co-installable
(libmariadb-dev-compat:amd64 Conflicts libmariadb-dev-compat:arm64). That is
a separate issue in the mariadb packaging and I will report it separately.

Thanks,
Dick Hollenbeck

The patch (Blocker 1) — trivial, and exactly what unstable already did.
Against the 1.13.0-6 source, in debian/control, the libpoco-dev stanza:

Package: libpoco-dev
Section: libdevel
Architecture: any
+Multi-Arch: same
Depends: ${misc:Depends},
libpocofoundation... (= ${binary:Version}),
...


-- System Information:
Debian Release: 13.4
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.12.74+deb13+1-amd64 (SMP w/16 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libpoco-dev depends on:
ii default-libmysqlclient-dev 1.1.1
ii libexpat1-dev 2.7.1-2
ii libpcre2-dev 10.46-1~deb13u1
pn libpocoactiverecord100 <none>
pn libpococrypto100 <none>
pn libpocodata100 <none>
pn libpocodatamysql100 <none>
pn libpocodataodbc100 <none>
pn libpocodatapostgresql100 <none>
pn libpocodatasqlite100 <none>
pn libpocoencodings100 <none>
pn libpocofoundation100 <none>
pn libpocojson100 <none>
pn libpocojwt100 <none>
pn libpocomongodb100 <none>
pn libpoconet100 <none>
pn libpoconetssl100 <none>
pn libpocoprometheus100 <none>
pn libpocoredis100 <none>
pn libpocoutil100 <none>
pn libpocoxml100 <none>
pn libpocozip100 <none>
ii libsqlite3-dev 3.46.1-7+deb13u1
ii libssl-dev 3.5.5-1~deb13u2
ii zlib1g-dev 1:1.3.dfsg+really1.3.1-1+b1

libpoco-dev recommends no packages.

libpoco-dev suggests no packages.