1.. _packaging:
2
3========================
4Advice on Packaging LLVM
5========================
6
7.. contents::
8   :local:
9
10Overview
11========
12
13LLVM sets certain default configure options to make sure our developers don't
14break things for constrained platforms.  These settings are not optimal for most
15desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
16etc.) will tweak them.  This document lists settings we suggest you tweak.
17
18LLVM's API changes with each release, so users are likely to want, for example,
19both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps developed
20against each.
21
22Compile Flags
23=============
24
25LLVM runs much more quickly when it's optimized and assertions are removed.
26However, such a build is currently incompatible with users who build without
27defining ``NDEBUG``, and the lack of assertions makes it hard to debug problems
28in user code.  We recommend allowing users to install both optimized and debug
29versions of LLVM in parallel.  The following configure flags are relevant:
30
31``--disable-assertions``
32    Builds LLVM with ``NDEBUG`` defined.  Changes the LLVM ABI.  Also available
33    by setting ``DISABLE_ASSERTIONS=0|1`` in ``make``'s environment.  This
34    defaults to enabled regardless of the optimization setting, but it slows
35    things down.
36
37``--enable-debug-symbols``
38    Builds LLVM with ``-g``.  Also available by setting ``DEBUG_SYMBOLS=0|1`` in
39    ``make``'s environment.  This defaults to disabled when optimizing, so you
40    should turn it back on to let users debug their programs.
41
42``--enable-optimized``
43    (For svn checkouts) Builds LLVM with ``-O2`` and, by default, turns off
44    debug symbols.  Also available by setting ``ENABLE_OPTIMIZED=0|1`` in
45    ``make``'s environment.  This defaults to enabled when not in a
46    checkout.
47
48C++ Features
49============
50
51RTTI
52    LLVM disables RTTI by default.  Add ``REQUIRES_RTTI=1`` to your environment
53    while running ``make`` to re-enable it.  This will allow users to build with
54    RTTI enabled and still inherit from LLVM classes.
55
56Shared Library
57==============
58
59Configure with ``--enable-shared`` to build
60``libLLVM-<major>.<minor>.(so|dylib)`` and link the tools against it.  This
61saves lots of binary size at the cost of some startup time.
62
63Dependencies
64============
65
66``--enable-libffi``
67    Depend on `libffi <http://sources.redhat.com/libffi/>`_ to allow the LLVM
68    interpreter to call external functions.
69
70``--with-oprofile``
71
72    Depend on `libopagent
73    <http://oprofile.sourceforge.net/doc/devel/index.html>`_ (>=version 0.9.4)
74    to let the LLVM JIT tell oprofile about function addresses and line
75    numbers.
76