[libc-commits] [libc] [libc] Rewrite "Full Host Build" instructions (PR #180439)

[Jeff Bailey via libc-commits]

================
@@ -13,36 +13,29 @@ Full Host Build
    pyyaml. The minimum versions are listed on the :ref:`header_generation`
    page, as well as additional information.
 
-In this document, we will present a recipe to build the full libc for the host.
-When we say *build the libc for the host*, the goal is to build the libc for
-the same system on which the libc is being built. First, we will explain how to
-build for developing LLVM-libc, then we will explain how to build LLVM-libc as
-part of a complete toolchain.
-
-Configure the build for development
-===================================
-
-
-Below is the list of commands for a simple recipe to build LLVM-libc for
-development. In this we've set the Ninja generator, set the build type to
-"Debug", and enabled the Scudo allocator. This build also enables generating the
-documentation and verbose cmake logging, which are useful development features.
+Standard Building and Testing
+=============================
 
 .. note::
-   if your build fails with an error saying the compiler can't find
+   If your build fails with an error saying the compiler can't find
    ``<asm/unistd.h>`` or similar then you're probably missing the symlink from
    ``/usr/include/asm`` to ``/usr/include/<HOST TRIPLE>/asm``. Installing the
    ``gcc-multilib`` package creates this symlink, or you can do it manually with
    this command:
    ``sudo ln -s /usr/include/<HOST TRIPLE>/asm /usr/include/asm``
    (your host triple will probably be similar to ``x86_64-linux-gnu``)
 
+For basic development, such as adding new functions or fixing bugs, you can build
+and test the libc directly without setting up a full sysroot. This approach
+is faster and sufficient for most contributors.
+
+To configure the build, create a build directory and run ``cmake``:
+
 .. code-block:: sh
 
-   $> cd llvm-project  # The llvm-project checkout
-   $> mkdir build
-   $> cd build
-   $> cmake ../runtimes \
+   cmake \
----------------
kaladron wrote:

The build tree will be created automatically if it does not already exist.  It looks like this behaviour was added at the same time as the -B and -S parameters were introduced.

https://cmake.org/cmake/help/latest/manual/cmake.1.html#generate-a-project-buildsystem

I could see us maybe setting a variable for $BUILD and using that throughout, but then if someone misses that when cutting and pasting they're going to get errors.  I found this out several times when running the instructions below and forgot to set SYSROOT. =/

https://github.com/llvm/llvm-project/pull/180439