From Linux Man Pages
dpkg-architecture - set and determine the architecture for package building
SYNOPSIS
dpkg-architecture [options] [action]
Valid options: -aDebian-Architecture -tGnu-System-Type -f
Valid actions: -l, -qVariable-Name, -s, -u, -c Command
DESCRIPTION
dpkg-architecture does provide a facility to determine and set the build and host architecture for package
building.
OVERVIEW
The build architecture is always determined by an external call to dpkg, and can not be set at the command line.
You can specify the host architecture by providing one or both of the options -a and -t. The default is
determined by an external call to gcc, or the same as the build architecture if CC or gcc are both not available.
One out of -a and -t is sufficient, the value of the other will be set to a usable default. Indeed, it is often
better to only specify one, because dpkg-architecture will warn you if your choice doesn't match the default.
The default action is -l, which prints the environment variales, one each line, in the format VARIABLE=value. If
you are only interested in the value of a single variable, you can use -q. If you specify -s, it will output an
export command. This can be used to set the environment variables using eval. -u does return a similar command to
unset all variables. -c does execute a command in an environment which has all variables set to the determined
value.
Existing environment variables with the same name as used by the scripts are not overwritten, except if the -f
force flag is present. This allows the user to override a value even when the call to dpkg-architecture is buried
in some other script (for example dpkg-buildpackage). The -q query option implies -f, and is therefore not
affected by existing environment settings.
TERMS
build machine
The machine the package is build on.
host machine
The machine the package is build for.
Debian Architecture
The Debian archietcture string, which specifies the binary tree in the FTP archive. Examples: i386, sparc,
hurd-i386.
GNU System Type
An architecture specification string consisting of two or three parts, cpu-system or cpu-vendor-system.
Examples: i386-linux, sparc-linux, i386-gnu.
EXAMPLES
dpkg-buildpackage accepts the -a option and passes it to dpkg-architecture. Other examples:
CC=i386-gnu-gcc dpkg-architecture -c debian/rules build
eval `dpkg-architecture -u`
VARIABLES
The following variables are set by dpkg-architecture:
DEB_BUILD_ARCH
The Debian architecture of the build machine.
DEB_BUILD_GNU_TYPE
The GNU system type of the build machine.
DEB_BUILD_GNU_CPU
The CPU part of DEB_BUILD_GNU_TYPE
DEB_BUILD_GNU_SYSTEM
The System part of DEB_BUILD_GNU_TYPE
DEB_HOST_ARCH
The Debian architecture of the host machine.
DEB_HOST_GNU_TYPE
The GNU system type of the host machine.
DEB_HOST_GNU_CPU
The CPU part of DEB_HOST_GNU_TYPE
DEB_HOST_GNU_SYSTEM
The System part of DEB_HOST_GNU_TYPE
DEBIAN/RULES
The environment variables set by dpkg-architecture are passed to debian/rules as make variables (see make
documentation). You can and should use them in the build process as needed. Here are some examples, which also
show how you can improve the cross compilation support in your package:
Instead:
ARCH=`dpkg --print-architecture` configure $(ARCH)-linux
please use the following:
B_ARCH=$(DEB_BUILD_GNU_TYPE) H_ARCH=$(DEB_HOST_GNU_TYPE) configure --build=$(B_ARCH) --host=$(H_ARCH)
Instead:
ARCH=`dpkg --print-architecture` ifeq ($(ARCH),alpha)
... endif
please use:
ARCH=$(DEB_HOST_ARCH) ifeq ($(ARCH),alpha)
... endif
In general, calling dpkg in the rules file to get architecture information is deprecated (until you want to
provide backward compatibility, see below). Especially the --print-architecture option is unreliable since we
have Debian architectures which don't equal a processor name.
BACKWARD COMPATIBILITY
When providing a new facility, it is always a good idea to stay compatible with old versions of the programs.
Note that dpkg-architecture does not affect old debian/rules files, so the only thing to consider is using old
building scripts with new debian/rules files. The following does the job:
DEB_BUILD_ARCH := $(shell dpkg --print-installation-architecture) DEB_BUILD_GNU_CPU := $(patsubst
hurd-%,%,$(DEB_BUILD_ARCH)) ifeq ($(filter-out hurd-%,$(DEB_BUILD_ARCH)),)
DEB_BUILD_GNU_SYSTEM := gnu else
DEB_BUILD_GNU_SYSTEM := linux endif DEB_BUILD_GNU_TYPE=$(DEB_BUILD_GNU_CPU)-$(DEB_BUILD_GNU_SYSTEM)
DEB_HOST_ARCH=$(DEB_BUILD_ARCH) DEB_HOST_GNU_CPU=$(DEB_BUILD_GNU_CPU) DEB_HOST_GNU_SYSTEM=$(DEB_BUILD_GNU_SYSTEM)
DEB_HOST_GNU_TYPE=$(DEB_BUILD_GNU_TYPE)
Put a subset of these lines at the top of your debian/rules file; these default values will be overwritten if
dpkg-architecture is used.
You don't need the full set. Choose a consistent set which contains the values you use in the rules file. For
example, if you only need the host Debian architecture, `DEB_HOST_ARCH=`dpkg --print-installation-architecture`
is sufficient (this is indeed the Debian architecture of the build machine, but remember that we are only trying
to be backward compatible with native compilation).
You may not want to care about old build packages (for example, if you have sufficient source dependencies
declared anyway). But you should at least support the traditional way to build packages by calling `debian/rules
build' directly, without setting environment variables. To do this, use the -q option to query suitable default
values:
DEB_BUILD_ARCH=`dpkg-architecture -qDEB_BUILD_ARCH` DEB_BUILD_GNU=`dpkg-architecture -qDEB_BUILD_GNU`
etc. You get the idea. This way, you can ensure that the variables are never undeclared. Note that this breaks
backwards compatibility with old build scripts, and you should only do that if source dependencies are
implemented and declared accordingly.
RELATED
dpkg-buildpackage dpkg-cross
CONTACT
If you have questions about the usage of the make variables in your rules files, or about cross compilation
support in your packages, please email me. The addresse is Marcus Brinkmann <brinkmd@debian.org>.
CATEGORY