watchman: first cut at making it build with buck in fbcode

Summary:
We can't just migrate wholesale to TARGETS because it is important to
keep our existing autoconf and windows build pieces working externally.

This diff adds probe.py as a light-weight alternative to autoconf that we can
use to probe certain things about the system and generate our config.h header
file.

We're using some native BUCK rules so that we can specify a header prefix so
that the includes will continue to work as-is without requiring an overhaul in
how the other build systems work with this code base.

This builds just the watchman binary for now.  Will follow up with plumbing in the tests.

Reviewed By: simpkins

Differential Revision: D3799750

fbshipit-source-id: ea7716ce521ec8766caf12b30771f964783a65f5

TARGETS

@@ -0,0 +1,182 @@
+# Things aren't as nice in here as we'd like, but that's because
+# we need to preserve how things build in the autoconf and windows
+# builds for watchman.
+
+# Generates 'config.h' by probing for system capabilities
+def prober():
+    import os
+
+    # We're going to extract the configured compiler from the buck config
+    # and pass that down to the probe script.
+    config_flags = {
+      'cc': 'cc_real',
+      'cppflags': 'cppflags',
+      'ldflags': 'ldflags',
+    }
+
+    probe_cmd = [
+        'python',
+        '$SRCDIR/probe.py',
+        '--configure=$SRCDIR/configure.ac',
+        '--cwd=%s' % os.getcwd()]
+
+    for name, key in config_flags.iteritems():
+        val = read_config('cxx', key)
+        probe_cmd.append("--%s='%s'" % (name, val))
+
+    probe_cmd.append('> $OUT')
+
+    buck_genrule(
+        name='generate_config_h',
+        srcs=[
+            'probe.py',
+            'configure.ac',
+        ],
+        cmd=' '.join(probe_cmd),
+        out='config.h',
+    )
+
+def config_h():
+    # we use this same convention in the eden build to discover whether
+    # we are building in the internal fb repo or in the opensourced project(s).
+    if read_config('codebase', 'mode') == 'public':
+        prober()
+    else:
+        # Just copy the pre-configured linux attributes so that we have
+        # know precisely what the characteristics will be for this build.
+        buck_genrule(
+            name='generate_config_h',
+            srcs=['facebook/linux_config.h'],
+            cmd='cp $SRCDIR/facebook/linux_config.h $OUT',
+            out='config.h',
+        )
+
+config_h()
+
+# Wraps the generated config.h file in a library rule that we can
+# depend upon.
+buck_cxx_library(
+    name='config_h',
+    exported_headers=[
+        ':generate_config_h',
+    ],
+    header_namespace="",
+    visibility=["PUBLIC"],
+)
+
+# Exports all watchman headers without the 'watchman/' prefix that
+# they would otherwise have in our build tree.
+buck_cxx_library(
+    name='headers',
+    exported_headers=glob(['**/*.h']),
+    header_namespace="",
+    visibility=["PUBLIC"],
+    exported_deps=[
+        ':config_h', '//watchman/thirdparty/jansson:config_h'
+    ],
+)
+
+# Linux specific watcher module
+cpp_library(
+    name='sysdep_watcher',
+    supported_platforms_regex='glibc',
+    srcs=['watcher/inotify.c'],
+    deps=[':headers', ':err'],
+)
+
+# mac specific watcher module
+cpp_library(
+    name='sysdep_watcher',
+    supported_platforms_regex='macos',
+    srcs=['watcher/fsevents.c', 'watcher/kqueue.c'],
+    deps=[':headers'],
+)
+
+# windows specific watcher module
+cpp_library(
+    name='sysdep_watcher',
+    supported_platforms_regex='windows',
+    srcs=['watcher/win32.c'],
+    deps=[':headers'],
+)
+
+cpp_library(name="log",
+            srcs=["log.c"],
+            deps=[':headers'], )
+
+cpp_library(name='hash',
+            srcs=['hash.c'],
+            deps=[':headers'], )
+
+cpp_library(name="string",
+            srcs=["string.c"],
+            deps=[':headers', ':hash'], )
+
+cpp_library(
+    name="err",
+    srcs=["root/warnerr.c", "root/poison.c"],
+    deps=[':headers'],
+)
+
+cpp_library(
+    name='pcre',
+    srcs=['query/pcre.c'],
+    deps=[':headers'],
+    compiler_flags=['-DHAVE_PCRE_H'],
+    external_deps=['pcre'],
+)
+
+cpp_library(
+    name='testsupport',
+    srcs=[
+        'argv.c',
+        'bser.c',
+        'cfg.c',
+        'expflags.c',
+        'ht.c',
+        'ignore.c',
+        'opendir.c',
+        'pending.c',
+        'time.c',
+    ],
+    deps=[
+        ':headers',
+        ':log',
+        ':string',
+        '@/watchman/thirdparty/jansson:jansson',
+        '@/watchman/thirdparty/libart/src:art',
+    ],
+)
+
+# The bulk of the watchman implementation lives in this library
+cpp_library(
+    name="watchmanlib",
+    srcs=glob(
+        ["*.c", "query/*.c", "watcher/auto.c", "root/*.c", "cmds/*.c"],
+        excludes=[
+            'main.c', 'stream_win.c', 'log.c', 'query/pcre.c', 'root/warnerr.c',
+            'root/poison.c'
+        ]
+    ),
+    deps=[
+        ':headers',
+        '@/watchman/thirdparty/jansson:jansson',
+        '@/watchman/thirdparty/libart/src:art',
+        '@/watchman/thirdparty/wildmatch:wildmatch',
+        ':sysdep_watcher',
+        ':log',
+        ':pcre',
+        ':string',
+        ':err',
+    ],
+)
+
+# and the watchman binary itself
+cpp_binary(
+    name="watchman",
+    srcs=["main.c"],
+    deps=[
+        ':headers',
+        ':watchmanlib',
+    ]
+)