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   5   <title>Advice on Packaging LLVM</title>
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  10 <h1>Advice on Packaging LLVM</h1>
  11 <ol>
  12   <li><a href="#overview">Overview</a></li>
  13   <li><a href="#compilation">Compile Flags</a></li>
  14   <li><a href="#cxx-features">C++ Features</a></li>
  15   <li><a href="#shared-library">Shared Library</a></li>
  16   <li><a href="#deps">Dependencies</a></li>
  17 </ol>
  18
  19 <!--=========================================================================-->
  20 <h2><a name="overview">Overview</a></h2>
  21 <!--=========================================================================-->
  22 <div>
  23
  24 <p>LLVM sets certain default configure options to make sure our developers don't
  25 break things for constrained platforms.  These settings are not optimal for most
  26 desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
  27 etc.) will tweak them.  This document lists settings we suggest you tweak.
  28 </p>
  29
  30 <p>LLVM's API changes with each release, so users are likely to want, for
  31 example, both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps
  32 developed against each.
  33 </p>
  34 </div>
  35
  36 <!--=========================================================================-->
  37 <h2><a name="compilation">Compile Flags</a></h2>
  38 <!--=========================================================================-->
  39 <div>
  40
  41 <p>LLVM runs much more quickly when it's optimized and assertions are removed.
  42 However, such a build is currently incompatible with users who build without
  43 defining NDEBUG, and the lack of assertions makes it hard to debug problems in
  44 user code.  We recommend allowing users to install both optimized and debug
  45 versions of LLVM in parallel.  The following configure flags are relevant:
  46 </p>
  47
  48 <dl>
  49   <dt><tt>--disable-assertions</tt></dt><dd>Builds LLVM with <tt>NDEBUG</tt>
  50   defined.  Changes the LLVM ABI.  Also available by setting
  51   <tt>DISABLE_ASSERTIONS=0|1</tt> in <tt>make</tt>'s environment.  This defaults
  52   to enabled regardless of the optimization setting, but it slows things
  53   down.</dd>
  54
  55   <dt><tt>--enable-debug-symbols</tt></dt><dd>Builds LLVM with <tt>-g</tt>.
  56   Also available by setting <tt>DEBUG_SYMBOLS=0|1</tt> in <tt>make</tt>'s
  57   environment.  This defaults to disabled when optimizing, so you should turn it
  58   back on to let users debug their programs.</dd>
  59
  60   <dt><tt>--enable-optimized</tt></dt><dd>(For svn checkouts) Builds LLVM with
  61   <tt>-O2</tt> and, by default, turns off debug symbols.  Also available by
  62   setting <tt>ENABLE_OPTIMIZED=0|1</tt> in <tt>make</tt>'s environment.  This
  63   defaults to enabled when not in a checkout.</dd>
  64 </dl>
  65 </div>
  66
  67 <!--=========================================================================-->
  68 <h2><a name="cxx-features">C++ Features</a></h2>
  69 <!--=========================================================================-->
  70 <div>
  71
  72 <dl>
  73   <dt>RTTI</dt><dd>LLVM disables RTTI by default.  Add <tt>REQUIRES_RTTI=1</tt>
  74   to your environment while running <tt>make</tt> to re-enable it.  This will
  75   allow users to build with RTTI enabled and still inherit from LLVM
  76   classes.</dd>
  77 </dl>
  78 </div>
  79
  80 <!--=========================================================================-->
  81 <h2><a name="shared-library">Shared Library</a></h2>
  82 <!--=========================================================================-->
  83 <div>
  84
  85 <p>Configure with <tt>--enable-shared</tt> to build
  86 <tt>libLLVM-<var>major</var>.<var>minor</var>.(so|dylib)</tt> and link the tools
  87 against it.  This saves lots of binary size at the cost of some startup time.
  88 </p>
  89 </div>
  90
  91 <!--=========================================================================-->
  92 <h2><a name="deps">Dependencies</a></h2>
  93 <!--=========================================================================-->
  94 <div>
  95
  96 <dl>
  97 <dt><tt>--enable-libffi</tt></dt><dd>Depend on <a
  98 href="http://sources.redhat.com/libffi/">libffi</a> to allow the LLVM
  99 interpreter to call external functions.</dd>
 100 <dt><tt>--with-oprofile</tt></dt><dd>Depend on <a
 101 href="http://oprofile.sourceforge.net/doc/devel/index.html">libopagent</a>
 102 (>=version 0.9.4) to let the LLVM JIT tell oprofile about function addresses and
 103 line numbers.</dd>
 104 </dl>
 105 </div>
 106
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