@c Copyright (C) 2001, 2002, 2004, 2008 Free Software Foundation, Inc.
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@c Copyright (C) 2001, 2002, 2004, 2008 Free Software Foundation, Inc.
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@c This is part of the GCC manual.
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@c This is part of the GCC manual.
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@c For copying conditions, see the file gcc.texi.
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@c For copying conditions, see the file gcc.texi.
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@node Configure Terms
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@node Configure Terms
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@section Configure Terms and History
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@section Configure Terms and History
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@cindex configure terms
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@cindex configure terms
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@cindex canadian
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@cindex canadian
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The configure and build process has a long and colorful history, and can
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The configure and build process has a long and colorful history, and can
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be confusing to anyone who doesn't know why things are the way they are.
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be confusing to anyone who doesn't know why things are the way they are.
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While there are other documents which describe the configuration process
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While there are other documents which describe the configuration process
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in detail, here are a few things that everyone working on GCC should
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in detail, here are a few things that everyone working on GCC should
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know.
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know.
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There are three system names that the build knows about: the machine you
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There are three system names that the build knows about: the machine you
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are building on (@dfn{build}), the machine that you are building for
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are building on (@dfn{build}), the machine that you are building for
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(@dfn{host}), and the machine that GCC will produce code for
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(@dfn{host}), and the machine that GCC will produce code for
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(@dfn{target}). When you configure GCC, you specify these with
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(@dfn{target}). When you configure GCC, you specify these with
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@option{--build=}, @option{--host=}, and @option{--target=}.
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@option{--build=}, @option{--host=}, and @option{--target=}.
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Specifying the host without specifying the build should be avoided, as
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Specifying the host without specifying the build should be avoided, as
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@command{configure} may (and once did) assume that the host you specify
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@command{configure} may (and once did) assume that the host you specify
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is also the build, which may not be true.
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is also the build, which may not be true.
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If build, host, and target are all the same, this is called a
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If build, host, and target are all the same, this is called a
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@dfn{native}. If build and host are the same but target is different,
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@dfn{native}. If build and host are the same but target is different,
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this is called a @dfn{cross}. If build, host, and target are all
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this is called a @dfn{cross}. If build, host, and target are all
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different this is called a @dfn{canadian} (for obscure reasons dealing
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different this is called a @dfn{canadian} (for obscure reasons dealing
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with Canada's political party and the background of the person working
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with Canada's political party and the background of the person working
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on the build at that time). If host and target are the same, but build
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on the build at that time). If host and target are the same, but build
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is different, you are using a cross-compiler to build a native for a
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is different, you are using a cross-compiler to build a native for a
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different system. Some people call this a @dfn{host-x-host},
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different system. Some people call this a @dfn{host-x-host},
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@dfn{crossed native}, or @dfn{cross-built native}. If build and target
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@dfn{crossed native}, or @dfn{cross-built native}. If build and target
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are the same, but host is different, you are using a cross compiler to
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are the same, but host is different, you are using a cross compiler to
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build a cross compiler that produces code for the machine you're
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build a cross compiler that produces code for the machine you're
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building on. This is rare, so there is no common way of describing it.
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building on. This is rare, so there is no common way of describing it.
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There is a proposal to call this a @dfn{crossback}.
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There is a proposal to call this a @dfn{crossback}.
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If build and host are the same, the GCC you are building will also be
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If build and host are the same, the GCC you are building will also be
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used to build the target libraries (like @code{libstdc++}). If build and host
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used to build the target libraries (like @code{libstdc++}). If build and host
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are different, you must have already built and installed a cross
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are different, you must have already built and installed a cross
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compiler that will be used to build the target libraries (if you
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compiler that will be used to build the target libraries (if you
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configured with @option{--target=foo-bar}, this compiler will be called
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configured with @option{--target=foo-bar}, this compiler will be called
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@command{foo-bar-gcc}).
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@command{foo-bar-gcc}).
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In the case of target libraries, the machine you're building for is the
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In the case of target libraries, the machine you're building for is the
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machine you specified with @option{--target}. So, build is the machine
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machine you specified with @option{--target}. So, build is the machine
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you're building on (no change there), host is the machine you're
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you're building on (no change there), host is the machine you're
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building for (the target libraries are built for the target, so host is
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building for (the target libraries are built for the target, so host is
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the target you specified), and target doesn't apply (because you're not
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the target you specified), and target doesn't apply (because you're not
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building a compiler, you're building libraries). The configure/make
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building a compiler, you're building libraries). The configure/make
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process will adjust these variables as needed. It also sets
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process will adjust these variables as needed. It also sets
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@code{$with_cross_host} to the original @option{--host} value in case you
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@code{$with_cross_host} to the original @option{--host} value in case you
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need it.
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need it.
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The @code{libiberty} support library is built up to three times: once
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The @code{libiberty} support library is built up to three times: once
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for the host, once for the target (even if they are the same), and once
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for the host, once for the target (even if they are the same), and once
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for the build if build and host are different. This allows it to be
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for the build if build and host are different. This allows it to be
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used by all programs which are generated in the course of the build
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used by all programs which are generated in the course of the build
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process.
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process.
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