ea471e2aa8
* Add various options so that it uses the build lld and compiler-rt * Add instructions on how to use the newly built libc * Remove trailing comments in code-block for cut and pastability Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D145878
67 lines
2.2 KiB
ReStructuredText
67 lines
2.2 KiB
ReStructuredText
.. _full_cross_build:
|
|
|
|
================
|
|
Full Cross Build
|
|
================
|
|
|
|
.. contents:: Table of Contents
|
|
:depth: 1
|
|
:local:
|
|
|
|
In this document, we will present a recipe to cross build a full libc. When we
|
|
say *cross build* a full libc, we mean that we will build the libc for a target
|
|
system which is not the same as the system on which the libc is being built.
|
|
For example, you could be building for a bare metal aarch64 *target* on a Linux
|
|
x86_64 *host*.
|
|
|
|
Configure the full cross build of the libc
|
|
==========================================
|
|
|
|
Below is a simple recipe to configure the libc for a cross build. In this,
|
|
we've set Ninja as the generator, and are building the full libc.
|
|
|
|
.. code-block:: sh
|
|
|
|
$> cd llvm-project # The llvm-project checkout
|
|
$> mkdir build
|
|
$> cd build
|
|
$> cmake ../llvm \
|
|
-G Ninja \
|
|
-DLLVM_ENABLE_PROJECTS=libc \
|
|
-DCMAKE_C_COMPILER=clang \
|
|
-DCMAKE_CXX_COMPILER=clang++ \
|
|
-DLLVM_LIBC_FULL_BUILD=ON \
|
|
-DLIBC_TARGET_TRIPLE=<Your target triple>
|
|
|
|
We will go over the special options passed to the ``cmake`` command above.
|
|
|
|
* **Enabled Projects** - Since we want to build the libc project, we list
|
|
``libc`` as the enabled project.
|
|
* **The full build option** - Since we want to build the full libc, we pass
|
|
``-DLLVM_LIBC_FULL_BUILD=ON``.
|
|
* **The target triple** - This is the target triple of the target for which
|
|
we are building the libc. For example, for a Linux 32-bit Arm target,
|
|
one can specify it as ``arm-linux-eabi``.
|
|
|
|
Build and install
|
|
=================
|
|
|
|
After configuring the build with the above ``cmake`` command, one can build the
|
|
the libc for the target with the following command:
|
|
|
|
.. code-block:: sh
|
|
|
|
$> ninja libc
|
|
|
|
The above ``ninja`` command will build the ``libc.a`` static archive for the
|
|
target specified with ``-DLIBC_TARGET_TRIPLE`` to the ``cmake`` command.
|
|
|
|
Building for bare metal
|
|
=======================
|
|
|
|
To build for bare metal, all one has to do is to specify the
|
|
`system <https://clang.llvm.org/docs/CrossCompilation.html#target-triple>`_
|
|
component of the target triple as ``none``. For example, to build for a
|
|
32-bit arm target on bare metal, one can use a target triple like
|
|
``arm-none-eabi``.
|