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354 lines
11 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>Creating an LLVM Project</title>
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</head>
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<body bgcolor=white>
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<center><h1>Creating an LLVM Project<br></h1></center>
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<!--===============================================================-->
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<h2><a name="a">Overview</a><hr></h2>
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<!--===============================================================-->
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The LLVM build system is designed to facilitate the building of third party
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projects that use LLVM header files, libraries, and tools. In order to use
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these facilities, a Makefile from a project must do the following things:
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<ol>
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<li>Set environment variables.
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<p>
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There are several environment variables that a Makefile needs to set to
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use the LLVM build system:
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<dl compact>
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<dt>LLVM_SRC_ROOT
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<dd>
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The root of the LLVM source tree.
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<p>
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<dt>LLVM_OBJ_ROOT
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<dd>
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The root of the LLVM object tree.
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<p>
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<dt>BUILD_SRC_ROOT
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<dd>
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The root of the project's source tree.
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<p>
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<dt>BUILD_OBJ_ROOT
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<dd>
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The root of the project's object tree.
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<p>
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<dt>BUILD_SRC_DIR
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<dd>
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The directory containing the current source to be compiled.
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<p>
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<dt>BUILD_OBJ_DIR
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<dd>
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The directory where the current source will place the new object
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files. This should always be the current directory.
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<p>
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<dt>LEVEL
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<dd>
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The relative path from the current directory to the root of the
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object tree.
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<p>
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</dl>
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<li>Include the LLVM Makefile.config from $(LLVM_OBJ_ROOT).
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<p>
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<li>Include the LLVM Makefile.rules from $(LLVM_SRC_ROOT).
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</ol>
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There are two ways that you can set all of these variables:
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<ol>
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<li>
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You can write your own Makefiles which hard-code these values.
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<li>
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You can use the pre-made LLVM sample project. This sample project
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includes Makefiles, a configure script that can be used to configure
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the location of LLVM, and the ability to support multiple object
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directories from a single source directory.
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</ol>
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This document assumes that you will base your project off of the LLVM
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sample project found in <tt>llvm/projects/sample</tt>. If you want to
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devise your own build system, studying the sample project and LLVM
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Makefiles will probably provide enough information on how to write your own
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Makefiles.
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<p>
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<!--===============================================================-->
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<h2><a name="a">Create a Project from the Sample Project</a><hr></h2>
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<!--===============================================================-->
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Follow these simple steps to start your project:
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<ol>
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<li>
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Copy the <tt>llvm/projects/sample</tt> directory to any place
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of your choosing. You can place it anywhere you like. Rename the
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directory to match the name of your project.
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<p>
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<li>
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Add your source code and Makefiles to your source tree.
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<p>
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<li>
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If you want your Makefiles to be configured by the
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<tt>configure</tt> script, or if you want to support multiple
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object directories, add your Makefiles to the <tt>configure</tt>
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script by adding them into the <tt>autoconf/configure.ac</tt> file.
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The macro <tt>AC_CONFIG_MAKEFILE</tt> will copy a file, unmodified,
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from the source directory to the object directory.
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<p>
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After updating <tt>autoconf/configure.ac</tt>, regenerate the
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configure script with these commands:
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<p>
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<tt>
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cd autoconf<br>
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autoconf -o ../configure
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</tt>
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<p>
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You must be using Autoconf version 2.57 or higher.
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<p>
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<li>
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Run <tt>configure</tt> in the directory in which you want to place
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object code. Use the following options to tell your project where it
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can find LLVM:
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<dl compact>
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<dt><tt>--with-llvmsrc=<directory></tt>
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<dd>
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Tell your project where the LLVM source tree is located.
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<p>
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<dt><tt>--with-llvmobj=<directory></tt>
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<dd>
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Tell your project where the LLVM object tree is located.
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</dl>
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</ol>
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That's it! Now all you have to do is type <tt>gmake</tt> in the root of
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your object directory, and your project should build.
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<!--===============================================================-->
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<h2><a name="Source Tree Layout">Source Tree Layout</a><hr></h2>
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<!--===============================================================-->
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In order to use the LLVM build system, you will want to organize your
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source code so that it can benefit from the build system's features.
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Mainly, you want your source tree layout to look similar to the LLVM
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source tree layout. The best way to do this is to just copy the
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project tree from <tt>llvm/projects/sample</tt> and modify it to meet
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your needs, but you can certainly add to it if you want.
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Underneath your top level directory, you should have the following
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directories:
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<dl compact>
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<dt><b>lib</b>
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<dd>
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This subdirectory should contain all of your library source
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code. For each library that you build, you will have one
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directory in <b>lib</b> that will contain that library's source
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code.
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<p>
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Libraries can be object files, archives, or dynamic libraries.
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The <b>lib</b> directory is just a convenient place for libraries
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as it places them all in a directory from which they can be linked
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later.
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<dt><b>include</b>
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<dd>
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This subdirectory should contain any header files that are
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global to your project. By global, we mean that they are used
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by more than one library or executable of your project.
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<p>
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By placing your header files in <b>include</b>, they will be
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found automatically by the LLVM build system. For example, if
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you have a file <b>include/jazz/note.h</b>, then your source
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files can include it simply with <b>#include "jazz/note.h"</b>.
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<dt><b>tools</b>
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<dd>
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This subdirectory should contain all of your source
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code for executables. For each program that you build, you
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will have one directory in <b>tools</b> that will contain that
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program's source code.
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</dl>
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Typically, you will want to build your <b>lib</b> directory first
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followed by your <b>tools</b> directory.
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<!--===============================================================-->
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<h2><a name="Makefile Variables">Writing LLVM Style Makefiles</a><hr></h2>
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<!--===============================================================-->
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The LLVM build system provides a convenient way to build libraries and
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executables. Most of your project Makefiles will only need to define a few
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variables. Below is a list of the variables one can set and what they can
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do:
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<h3> Required Variables </h3>
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<dl compact>
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<dt>LEVEL
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<dd>
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This variable is the relative path from this Makefile to the
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top directory of your project's source code. For example, if
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your source code is in /tmp/src, then the Makefile in
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/tmp/src/jump/high would set LEVEL to "../..".
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</dl>
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<h3> Variables for Building Subdirectories</h3>
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<dl compact>
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<dt>DIRS
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<dd>
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This is a space separated list of subdirectories that should be
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built. They will be built, one at a time, in the order
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specified.
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<p>
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<dt>PARALLEL_DIRS
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<dd>
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This is a list of directories that can be built in parallel.
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These will be built after the directories in DIRS have been
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built.
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<p>
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<dt>OPTIONAL_DIRS
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<dd>
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This is a list of directories that can be built if they exist,
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but will not cause an error if they do not exist. They are
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built serially in the order in which they are listed.
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</dl>
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<h3> Variables for Building Libraries</h3>
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<dl compact>
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<dt>LIBRARYNAME
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<dd>
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This variable contains the base name of the library that will
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be built. For example, to build a library named
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<tt>libsample.a</tt>, LIBRARYNAME should be set to
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<tt>sample</tt>.
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<p>
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<dt>BUILD_ARCHIVE
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<dd>
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By default, a library is a <tt>.o</tt> file that is linked
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directly into a program. To build an archive (also known as
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a static library), set the BUILD_ARCHIVE variable.
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<p>
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<dt>SHARED_LIBRARY
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<dd>
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If SHARED_LIBRARY is defined in your Makefile, a shared
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(or dynamic) library will be built.
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</dl>
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<h3> Variables for Building Programs</h3>
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<dl compact>
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<dt>TOOLNAME
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<dd>
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This variable contains the name of the program that will
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be built. For example, to build an executable named
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<tt>sample</tt>, TOOLNAME should be set to <tt>sample</tt>.
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<p>
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<dt>USEDLIBS
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<dd>
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This variable holds a space separated list of libraries that
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should be linked into the program. These libraries must either
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be LLVM libraries or libraries that come from your <b>lib</b>
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directory. The libraries must be specified by their base name.
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For example, to link libsample.a, you would set USEDLIBS to
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<tt>sample</tt>.
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<p>
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Note that this works only for statically linked libraries.
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<p>
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<dt>LIBS
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<dd>
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To link dynamic libraries, add <tt>-l<library base name></tt> to
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the LIBS variable. The LLVM build system will look in the same places
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for dynamic libraries as it does for static libraries.
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<p>
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For example, to link <tt>libsample.so</tt>, you would have the
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following line in your <tt>Makefile</tt>:
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<p>
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<tt>
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LIBS+=-lsample
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</tt>
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</dl>
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<h3> Miscellaneous Variables</h3>
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<dl compact>
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<dt>ExtraSource
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<dd>
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This variable contains a space separated list of extra source
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files that need to be built. It is useful for including the
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output of Lex and Yacc programs.
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<p>
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<dt>CFLAGS
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<dt>CPPFLAGS
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<dd>
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This variable can be used to add options to the C and C++
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compiler, respectively. It is typically used to add options
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that tell the compiler the location of additional directories
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to search for header files.
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<p>
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It is highly suggested that you append to CFLAGS and CPPFLAGS as
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opposed to overwriting them. The master Makefiles may already
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have useful options in them that you may not want to overwrite.
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<p>
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</dl>
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<!--===============================================================-->
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<h2><a name="objcode">Placement of Object Code</a><hr></h2>
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<!--===============================================================-->
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The final location of built libraries and executables will depend upon
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whether you do a Debug, Release, or Profile build.
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<dl compact>
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<dt>Libraries
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<dd>
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All libraries (static and dynamic) will be stored in
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BUILD_OBJ_ROOT/lib/<type>, where type is <tt>Debug</tt>,
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<tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or
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profiled build, respectively.
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<p>
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<dt>Executables
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<dd>
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All executables will be stored in BUILD_OBJ_ROOT/lib/<type>,
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where type is <tt>Debug</tt>, <tt>Release</tt>, or <tt>Profile</tt> for
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a debug, optimized, or profiled build, respectively.
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</dl>
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<!--===============================================================-->
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<h2><a name="help">Further Help</a><hr></h2>
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<!--===============================================================-->
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If you have any questions or need any help creating an LLVM project,
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the LLVM team would be more than happy to help. You can always post your
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questions to the LLVM Developers Mailing List (<a
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href="mailto:llvmdev.cs.uiuc.edu">llvmdev@cs.uiuc.edu</a>).
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<hr>
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Written by <a href="mailto:criswell@uiuc.edu">John Criswell</a>.
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</body>
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</html>
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