contrib/python-zstandard/make_cffi.py

dirstate: fix restoration of "merged" state after a remove

Before this change, "merged" file that get removed and re-added later were
recorded as "from_p2" instead.

This came from 8fe74328f700, a 2014 changeset that start explicitly doing so
for reason I have not been able to fully grasp.  The graft test mentioned in
the description are still happy after this changeset.

So this changeset restore what seems to be the intended behavior. Restoring
information as it was before the removal.

Differential Revision: https://phab.mercurial-scm.org/D11429

# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.

from __future__ import absolute_import

import cffi
import distutils.ccompiler
import os
import re
import subprocess
import tempfile


HERE = os.path.abspath(os.path.dirname(__file__))

SOURCES = [
    "zstd/%s" % p
    for p in (
        "common/debug.c",
        "common/entropy_common.c",
        "common/error_private.c",
        "common/fse_decompress.c",
        "common/pool.c",
        "common/threading.c",
        "common/xxhash.c",
        "common/zstd_common.c",
        "compress/fse_compress.c",
        "compress/hist.c",
        "compress/huf_compress.c",
        "compress/zstd_compress.c",
        "compress/zstd_compress_literals.c",
        "compress/zstd_compress_sequences.c",
        "compress/zstd_double_fast.c",
        "compress/zstd_fast.c",
        "compress/zstd_lazy.c",
        "compress/zstd_ldm.c",
        "compress/zstd_opt.c",
        "compress/zstdmt_compress.c",
        "decompress/huf_decompress.c",
        "decompress/zstd_ddict.c",
        "decompress/zstd_decompress.c",
        "decompress/zstd_decompress_block.c",
        "dictBuilder/cover.c",
        "dictBuilder/fastcover.c",
        "dictBuilder/divsufsort.c",
        "dictBuilder/zdict.c",
    )
]

# Headers whose preprocessed output will be fed into cdef().
HEADERS = [
    os.path.join(HERE, "zstd", *p)
    for p in (
        ("zstd.h",),
        ("dictBuilder", "zdict.h"),
    )
]

INCLUDE_DIRS = [
    os.path.join(HERE, d)
    for d in (
        "zstd",
        "zstd/common",
        "zstd/compress",
        "zstd/decompress",
        "zstd/dictBuilder",
    )
]

# cffi can't parse some of the primitives in zstd.h. So we invoke the
# preprocessor and feed its output into cffi.
compiler = distutils.ccompiler.new_compiler()

# Needed for MSVC.
if hasattr(compiler, "initialize"):
    compiler.initialize()

# Distutils doesn't set compiler.preprocessor, so invoke the preprocessor
# manually.
if compiler.compiler_type == "unix":
    args = list(compiler.executables["compiler"])
    args.extend(
        [
            "-E",
            "-DZSTD_STATIC_LINKING_ONLY",
            "-DZDICT_STATIC_LINKING_ONLY",
        ]
    )
elif compiler.compiler_type == "msvc":
    args = [compiler.cc]
    args.extend(
        [
            "/EP",
            "/DZSTD_STATIC_LINKING_ONLY",
            "/DZDICT_STATIC_LINKING_ONLY",
        ]
    )
else:
    raise Exception("unsupported compiler type: %s" % compiler.compiler_type)


def preprocess(path):
    with open(path, "rb") as fh:
        lines = []
        it = iter(fh)

        for l in it:
            # zstd.h includes <stddef.h>, which is also included by cffi's
            # boilerplate. This can lead to duplicate declarations. So we strip
            # this include from the preprocessor invocation.
            #
            # The same things happens for including zstd.h, so give it the same
            # treatment.
            #
            # We define ZSTD_STATIC_LINKING_ONLY, which is redundant with the inline
            # #define in zstdmt_compress.h and results in a compiler warning. So drop
            # the inline #define.
            if l.startswith(
                (
                    b"#include <stddef.h>",
                    b'#include "zstd.h"',
                    b"#define ZSTD_STATIC_LINKING_ONLY",
                )
            ):
                continue

            # The preprocessor environment on Windows doesn't define include
            # paths, so the #include of limits.h fails. We work around this
            # by removing that import and defining INT_MAX ourselves. This is
            # a bit hacky. But it gets the job done.
            # TODO make limits.h work on Windows so we ensure INT_MAX is
            # correct.
            if l.startswith(b"#include <limits.h>"):
                l = b"#define INT_MAX 2147483647\n"

            # ZSTDLIB_API may not be defined if we dropped zstd.h. It isn't
            # important so just filter it out.
            if l.startswith(b"ZSTDLIB_API"):
                l = l[len(b"ZSTDLIB_API ") :]

            lines.append(l)

    fd, input_file = tempfile.mkstemp(suffix=".h")
    os.write(fd, b"".join(lines))
    os.close(fd)

    try:
        env = dict(os.environ)
        if getattr(compiler, "_paths", None):
            env["PATH"] = compiler._paths
        process = subprocess.Popen(
            args + [input_file], stdout=subprocess.PIPE, env=env
        )
        output = process.communicate()[0]
        ret = process.poll()
        if ret:
            raise Exception("preprocessor exited with error")

        return output
    finally:
        os.unlink(input_file)


def normalize_output(output):
    lines = []
    for line in output.splitlines():
        # CFFI's parser doesn't like __attribute__ on UNIX compilers.
        if line.startswith(b'__attribute__ ((visibility ("default"))) '):
            line = line[len(b'__attribute__ ((visibility ("default"))) ') :]

        if line.startswith(b"__attribute__((deprecated("):
            continue
        elif b"__declspec(deprecated(" in line:
            continue

        lines.append(line)

    return b"\n".join(lines)


ffi = cffi.FFI()
# zstd.h uses a possible undefined MIN(). Define it until
# https://github.com/facebook/zstd/issues/976 is fixed.
# *_DISABLE_DEPRECATE_WARNINGS prevents the compiler from emitting a warning
# when cffi uses the function. Since we statically link against zstd, even
# if we use the deprecated functions it shouldn't be a huge problem.
ffi.set_source(
    "_zstd_cffi",
    """
#define MIN(a,b) ((a)<(b) ? (a) : (b))
#define ZSTD_STATIC_LINKING_ONLY
#include <zstd.h>
#define ZDICT_STATIC_LINKING_ONLY
#define ZDICT_DISABLE_DEPRECATE_WARNINGS
#include <zdict.h>
""",
    sources=SOURCES,
    include_dirs=INCLUDE_DIRS,
    extra_compile_args=["-DZSTD_MULTITHREAD"],
)

DEFINE = re.compile(b"^\\#define ([a-zA-Z0-9_]+) ")

sources = []

# Feed normalized preprocessor output for headers into the cdef parser.
for header in HEADERS:
    preprocessed = preprocess(header)
    sources.append(normalize_output(preprocessed))

    # #define's are effectively erased as part of going through preprocessor.
    # So perform a manual pass to re-add those to the cdef source.
    with open(header, "rb") as fh:
        for line in fh:
            line = line.strip()
            m = DEFINE.match(line)
            if not m:
                continue

            if m.group(1) == b"ZSTD_STATIC_LINKING_ONLY":
                continue

            # The parser doesn't like some constants with complex values.
            if m.group(1) in (b"ZSTD_LIB_VERSION", b"ZSTD_VERSION_STRING"):
                continue

            # The ... is magic syntax by the cdef parser to resolve the
            # value at compile time.
            sources.append(m.group(0) + b" ...")

cdeflines = b"\n".join(sources).splitlines()
cdeflines = [l for l in cdeflines if l.strip()]
ffi.cdef(b"\n".join(cdeflines).decode("latin1"))

if __name__ == "__main__":
    ffi.compile()