contrib: macdeploy: Correctly generate macOS SDK

Previously, we did not include the macOS SDK libc++ headers in our SDK
creation process and instead used whichever libc++ headers shipped with
the clang package we downloaded in depends.

This change adds a script (which works on both GNU/Linux and macOS) to
correctly generate the macOS SDK including the libc++ headers. This can
be thought of as a simplified rewrite of tpoechtrager's script:

https://github.com/tpoechtrager/osxcross/blob/d3392f4eae78f3fa3f1fd065fa423f2712825102/tools/gen_sdk_package.sh

The location within the SDK where we place the libc++ headers is chosen
such that clang's search path detection logic for sysroots would pick up
the headers properly.

We also document this change.

1 files changed, 94 insertions, 0 deletions

diff --git a/contrib/macdeploy/gen-sdk b/contrib/macdeploy/gen-sdk
new file mode 100755
index 0000000000..457d8f5e64
--- /dev/null
+++ b/contrib/macdeploy/gen-sdk
@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+import argparse
+import plistlib
+import pathlib
+import sys
+import tarfile
+import gzip
+import os
+import contextlib
+
+@contextlib.contextmanager
+def cd(path):
+    """Context manager that restores PWD even if an exception was raised."""
+    old_pwd = os.getcwd()
+    os.chdir(str(path))
+    try:
+        yield
+    finally:
+        os.chdir(old_pwd)
+
+def run():
+    parser = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawTextHelpFormatter)
+
+    parser.add_argument('xcode_app', metavar='XCODEAPP', nargs=1)
+    parser.add_argument("-o", metavar='OUTSDKTGZ', nargs=1, dest='out_sdktgz', required=False)
+
+    args = parser.parse_args()
+
+    xcode_app = pathlib.Path(args.xcode_app[0]).resolve()
+    assert xcode_app.is_dir(), "The supplied Xcode.app path '{}' either does not exist or is not a directory".format(xcode_app)
+
+    xcode_app_plist = xcode_app.joinpath("Contents/version.plist")
+    with xcode_app_plist.open('rb') as fp:
+        pl = plistlib.load(fp)
+        xcode_version = pl['CFBundleShortVersionString']
+        xcode_build_id = pl['ProductBuildVersion']
+    print("Found Xcode (version: {xcode_version}, build id: {xcode_build_id})".format(xcode_version=xcode_version, xcode_build_id=xcode_build_id))
+
+    sdk_dir = xcode_app.joinpath("Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk")
+    sdk_plist = sdk_dir.joinpath("System/Library/CoreServices/SystemVersion.plist")
+    with sdk_plist.open('rb') as fp:
+        pl = plistlib.load(fp)
+        sdk_version = pl['ProductVersion']
+        sdk_build_id = pl['ProductBuildVersion']
+    print("Found MacOSX SDK (version: {sdk_version}, build id: {sdk_build_id})".format(sdk_version=sdk_version, sdk_build_id=sdk_build_id))
+
+    out_name = "Xcode-{xcode_version}-{xcode_build_id}-extracted-SDK-with-libcxx-headers".format(xcode_version=xcode_version, xcode_build_id=xcode_build_id)
+
+    xcode_libcxx_dir = xcode_app.joinpath("Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1")
+    assert xcode_libcxx_dir.is_dir()
+
+    if args.out_sdktgz:
+        out_sdktgz_path = pathlib.Path(args.out_sdktgz_path)
+    else:
+        # Construct our own out_sdktgz if not specified on the command line
+        out_sdktgz_path = pathlib.Path("./{}.tar.gz".format(out_name))
+
+    def tarfp_add_with_base_change(tarfp, dir_to_add, alt_base_dir):
+        """Add all files in dir_to_add to tarfp, but prepent MEMBERPREFIX to the files'
+        names
+
+        e.g. if the only file under /root/bazdir is /root/bazdir/qux, invoking:
+
+            tarfp_add_with_base_change(tarfp, "foo/bar", "/root/bazdir")
+
+        would result in the following members being added to tarfp:
+
+            foo/bar/             -> corresponding to /root/bazdir
+            foo/bar/qux          -> corresponding to /root/bazdir/qux
+
+        """
+        def change_tarinfo_base(tarinfo):
+            if tarinfo.name and tarinfo.name.startswith("./"):
+                tarinfo.name = str(pathlib.Path(alt_base_dir, tarinfo.name))
+            if tarinfo.linkname and tarinfo.linkname.startswith("./"):
+                tarinfo.linkname = str(pathlib.Path(alt_base_dir, tarinfo.linkname))
+            return tarinfo
+        with cd(dir_to_add):
+            tarfp.add(".", recursive=True, filter=change_tarinfo_base)
+
+    print("Creating output .tar.gz file...")
+    with out_sdktgz_path.open("wb") as fp:
+        with gzip.GzipFile(fileobj=fp, compresslevel=9, mtime=0) as gzf:
+            with tarfile.open(mode="w", fileobj=gzf) as tarfp:
+                print("Adding MacOSX SDK {} files...".format(sdk_version))
+                tarfp_add_with_base_change(tarfp, sdk_dir, out_name)
+                print("Adding libc++ headers...")
+                tarfp_add_with_base_change(tarfp, xcode_libcxx_dir, "{}/usr/include/c++/v1".format(out_name))
+    print("Done! Find the resulting gzipped tarball at:")
+    print(out_sdktgz_path.resolve())
+
+if __name__ == '__main__':
+    run()