Advice on Packaging LLVM
- Compile Flags
- C++ Features
- Shared Library
LLVM sets certain default configure options to make sure our developers don't
break things for constrained platforms. These settings are not optimal for most
desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
etc.) will tweak them. This document lists settings we suggest you tweak.
LLVM's API changes with each release, so users are likely to want, for
example, both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps
developed against each.
LLVM runs much more quickly when it's optimized and assertions are removed.
However, such a build is currently incompatible with users who build without
defining NDEBUG, and the lack of assertions makes it hard to debug problems in
user code. We recommend allowing users to install both optimized and debug
versions of LLVM in parallel. The following configure flags are relevant:
- Builds LLVM with NDEBUG
defined. Changes the LLVM ABI. Also available by setting
DISABLE_ASSERTIONS=0|1 in make's environment. This defaults
to enabled regardless of the optimization setting, but it slows things
- Builds LLVM with -g.
Also available by setting DEBUG_SYMBOLS=0|1 in make's
environment. This defaults to disabled when optimizing, so you should turn it
back on to let users debug their programs.
- (For svn checkouts) Builds LLVM with
-O2 and, by default, turns off debug symbols. Also available by
setting ENABLE_OPTIMIZED=0|1 in make's environment. This
defaults to enabled when not in a checkout.
- LLVM disables RTTI by default. Add REQUIRES_RTTI=1
to your environment while running make to re-enable it. This will
allow users to build with RTTI enabled and still inherit from LLVM
Configure with --enable-shared to build
libLLVM-major.minor.(so|dylib) and link the tools
against it. This saves lots of binary size at the cost of some startup time.
- Depend on libffi to allow the LLVM
interpreter to call external functions.
- Depend on libopagent
(>=version 0.9.4) to let the LLVM JIT tell oprofile about function addresses and
The LLVM Compiler Infrastructure
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