[LLDB] Add utility to streamline Xcode project generation.

[JDevlieghere]

Summary

This is a follow-up to D65109 which removes the Xcode project. It seems that the script to generate the Xcode project was the most controversial, so I've split it off into a separate review.

From the original patch:

I created a new script to streamline the process: it creates two build directories in the current directory. The first directory is for LLVM and Clang which uses Ninja to build. The second directory is for LLBD, which configures a standalone build using the Xcode generator.

[JDevlieghere]

Currently outstanding questions are:

@clayborg

Not sure why we need two different build directories? Can we just use the mono-repo style build and use "cmake -G Xcode"? Or is this just to appease the Apple build process?

@lanza

This could probably be just a 10 line make file that you just make -f lldb/utils/xcode.mk. Not sure if you guys are a fan of this method, but we tend to find it to be much more manageable than custom python scripts.

[labath]

lldb/utils/xcode.py

33

You can get rid of the chdir stuff by just running cmake -S$SOURCE_DIR -B$BUILD_DIR && ninja -C $BUILD_DIR.

[sgraenitz]

Can we just use the mono-repo style build and use "cmake -G Xcode"?

Yes you can, but then you have all of llvm/clang/libcxx/lldb in one project. For LLDB development that's usually not necessary. (And also, for Xcode it's a bit overwhelming.)

I've included a new script to streamline the process

It's not so much of my business and we may disagree, but I am not sure it's a good idea to add an automation layer on-top of a meta-build-system. Remember build-script.

[JDevlieghere]

It's been a week and so far I haven't seen any complaints. Also I think the documentation Stefan added on lldb.llvm.org look good enough that we may not need a script.

lldb/utils/xcode.py

+#!/usr/bin/env python
+
+import sys
+import os
+import errno
+import subprocess
+import six
+from contextlib import contextmanager
+
+
+def mkdir(directory):
+    try:
+        os.makedirs(directory)
+    except OSError as e:
+        if e.errno != errno.EEXIST:
+            raise
+
+
+@contextmanager
+def cwd(path):
+    oldpwd = os.getcwd()
+    os.chdir(path)
+    try:
+        yield
+    finally:
+        os.chdir(oldpwd)
+
+
+def build_llvm(llvm_path):
+    """Configures and builds LLVM & Clang with Ninja."""
+    build_path = os.path.join(os.getcwd(), 'llvm-build')
+    mkdir(build_path)
+    with cwd(build_path):
+        cmake_cmd = [
+            "cmake {}".format(llvm_path), "-GNinja",
+            "-DCMAKE_BUILD_TYPE='Release'", "-DLLVM_ENABLE_ASSERTIONS:BOOL=ON",
+            "-DLLVM_ENABLE_PROJECTS='clang;libcxx;libcxxabi'"
+        ]
+        subprocess.call(' '.join(cmake_cmd), shell=True)
+        subprocess.call('ninja', shell=True)
+    return build_path
+
+
+def configure_lldb(llvm_build_path, lldb_path, args):
+    """Configures an standalone build of LLDB with the Xcode generator."""
+    build_path = os.path.join(os.getcwd(), 'lldb-build')
+    cache_path = os.path.join(lldb_path, 'cmake', 'caches',
+                              'Apple-lldb-Xcode.cmake')
+    llvm_dir = os.path.join(llvm_build_path, 'lib', 'cmake', 'llvm')
+    clang_dir = os.path.join(llvm_build_path, 'lib', 'cmake', 'clang')
+    mkdir(build_path)
+    with cwd(build_path):
+        cmake_cmd = [
+            "cmake {}".format(lldb_path), "-GXcode", "-C{}".format(cache_path),
+            "-DLLVM_DIR='{}'".format(llvm_dir),
+            "-DClang_DIR='{}'".format(clang_dir)
+        ]
+        cmake_cmd.extend(args)
+        subprocess.call(' '.join(cmake_cmd), shell=True)
+        subprocess.call('open lldb.xcodeproj', shell=True)
+    return build_path
+
+
+def main():
+    """Generate an Xcode project for LLDB from CMake.
+
+    This scripts creates two build directories in the current directory: one
+    for LLVM and one for LLDB. The LLVM build uses the Ninja generator, the
+    LLDB build uses the Xcode generator.
+    """
+    args = sys.argv[1:]
+    lldb_path = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
+    llvm_path = os.path.join(os.path.dirname(lldb_path), 'llvm')
+
+    if not os.path.exists(llvm_path):
+        printf('This script only works with the LLVM monorepo')
+        exit(1)
+
+    llvm_build_path = build_llvm(llvm_path)
+    lldb_build_path = configure_lldb(llvm_build_path, lldb_path, args)
+
+
+if __name__ == "__main__":
+    main()