perl-cross-debian - Online in the Cloud

PROGRAM:

NAME

perl-cross-debian - Long term maintenance of cross-build support for the Debian
configuration of perl

SYNOPSIS

perl-cross-debian [--rootdir=DIRECTORY] --variant=STRING

perl-cross-debian --clean

perl-cross-debian [{-h | --help} | {-v | --version}]

DESCRIPTION

perl-cross-debian supports the long term maintenance of cross-build support for the Debian
configuration of perl.

perl-cross-debian is not expected to be run directly on the command line, it is executed
by the modified debian/rules of a Debian source package of perl, within the constraints of
a cross-build. perl-cross-debian uses the cross-building environment set by
dpkg-architecture -aARCH to provide essential configuration values for the requested
architecture to avoid executing cross-built binaries within the cross-build. Full support
is limited to specific versions of perl already packaged in Debian and only for selected
architectures.

perl-cross-debian copies pre-produced config files into the current perl build tree to
prevent the build from needing to execute test binaries during the configuration stage by
providing the values of the tests in advance. perl-cross-debian then extracts values from
the cached files to update the build information and package Makefiles.

perl-cross-debian then relies on a patched Makefile.SH to call the host perl interpreter
instead of the perl interpreter being built internally.

See Running the cross build for details of how to prepare the Debian packages of perl for
cross-building for the one of the currently supported host architectures. (Patches to
apply to supported Debian versions of perl are included in
/usr/share/perl-cross-debian/patches).

See perl-cross-staging (1) for information on how to extend perl-cross-debian to other
host architectures and other versions of perl.

COMMAND

--variant VARIANT
Name of the current perl build variant (static, debug or shared), passed in via
debian/rules, must be specified once for each iteration.

--clean
Runs the perl-cross-debian clean target and exits zero. --clean overrides any
--variant command - the clean operation does not depend on the current variant.

OPTIONS

--rootdir DIRECTORY
Debug support for testing with unreleased config files, uses the files from the
rootdir instead of looking in the
/usr/share/perl-cross-debian/$(DEB_HOST_GNU_TYPE)/$(PERL_VERSION) directory.
($(PERL_VERSION) in this instance is the output of /bin/bash debian/config.debian
--full-version.)

-?, -h, --help, --version
Show summary of options and the version information.

LIMITATIONS

perl-cross-debian implements a safeguard that the perl interpreter to be used during the
cross-build is the same upstream version as the perl interpreter to be cross-built due to
limitations of DynaLoader.pm :

arm-linux-gnueabi-gcc -c -D_REENTRANT -D_GNU_SOURCE -DDEBIAN -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector
--param=ssp-buffer-size=4 -Wformat -Werror=format-security -fno-strict-aliasing -pipe -I/usr/local/include
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g -DVERSION=\"3.39_02\" -DXS_VERSION=\"3.39_02\"
-fPIC "-I../.." Cwd.c
Running Mkbootstrap for Cwd ()
DynaLoader object version 1.13 does not match $DynaLoader::VERSION 1.14 at ../../lib/DynaLoader.pm line 86.
Compilation failed in require at ../../lib/ExtUtils/Mkbootstrap.pm line 27.

Instead, perl-cross-debian dies with a version mismatch and fails the cross-build. Ensure
that the installed perl interpreter is upgraded before testing a cross-build of the
updated perl source code (or use a chroot). When using a chroot and old-style dpkg-cross
dependencies, consider preparing at least the zlib and bzip2 dependencies outside the
chroot as a new version of perl is frequently not installable with lots of perl modules
such as those used by dpkg-cross. e.g. zlib1g-dev-armel-cross and libbz2-dev-armel-cross
as well as libdb-dev-armel-cross and libgdbm-dev-armel-cross.

sudo xapt -a armel -b zlib1g-dev libbz2-dev libdb-dev libgdbm-dev

The -cross packages are in /var/lib/xapt/output and need to be copied into the chroot and
installed with dpkg -i ./*

perl-cross-debian also implements a safeguard to prevent cross-builds when
DEB_BUILD_OPTIONS="nocheck" has not been set prior to starting the build. Cross-build
failures due to the running of test code within the perl build are not always easy to
identify, so perl-cross-debian checks for this build option and fails the cross-build if
it is not set. (The check occurs inside perl-cross-debian so the clean target will have
been run before the check is made.)

RUNNING THE CROSS BUILD

perl-cross-debian needs some changes to the perl package before cross-building, so ensure
that Makefile.SH and debian/rules are both patched and that the cross dependencies and
cross compiler are installed.

Patches are carried in the perl-cross-debian package in
/usr/share/perl-cross-debian/patches.

debuild is preferred as this will provide a build log and run lintian (by default) which
means that the built packages will be checked to ensure that the binaries have been
correctly compiled for the cross architecture (amongst the normal checks). Run the cross
build with:

DEB_BUILD_OPTIONS="nocheck" debuild -aarmel -us -uc -d

Note the use of the -d option as dpkg cannot check cross-build dependencies until MutiArch
-dev packages are in use and the requirement for DEB_BUILD_OPTIONS to disable the test
suite.

SUPPORTED VERSIONS AND ARCHITECTURES

perl-cross-debian support is patchy but can be improved. Only specific architectures at
specific versions are supported - if you do not find the files for the requested version
in the directory of the architecture required, see perl-cross-staging (1) for information
on how this information can be added and also for details of ongoing work with perl
upstream.

CLEAN TARGET SUPPORT

perl-cross-debian includes support for a custom clean target for cross-builds to ensure
that version-specific content generated during the cross-build is cleaned up before
dpkg-source tries to verify the source package. If there are additional files which need
to be cleaned, file a bug against perl-cross-debian.

EXTENSION INSTALLATION

The current method of building and installing the extensions does need testing and
improvement. Whilst the main emphasis for a perl cross build is to support bootstrapping
by having the normal perl interpreter available instead of just miniperl, there may be
less emphasis on the correct functioning of the extensions and modules normally packaged
by a native perl build. Problems relating to any use of perl extensions and modules when
the cross built perl packages are installed should be reported as bugs in
perl-cross-debian.

EXTENDING PERL-CROSS-DEBIAN

perl-cross-debian provides some POD documentation of how to extend support to new
architectures and how to update existing support for new versions of perl.

See /usr/share/doc/perl-cross-debian/converting-native.pod and
/usr/share/doc/perl-cross-debian/new-arch.pod

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