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DPKG-ARCHITECTURE !!!DPKG-ARCHITECTURE NAME SYNOPSIS DESCRIPTION OVERVIEW TERMS EXAMPLES VARIABLES DEBIAN/RULES BACKWARD COMPATIBILITY SEE ALSO CONTACT ---- !!NAME dpkg-architecture - set and determine the architecture for package building !!SYNOPSIS dpkg-architecture [[options] [[action] Valid options: __-a__Debian-Architecture __-t__Gnu-System-Type __-f__ Valid actions: __-l__, __-q__Variable-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). !!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. !!SEE ALSO 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 address is Marcus Brinkmann ----
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