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# Copyright 2019 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import math
import os
import re
import subprocess
import SCons
from pkg_resources import parse_version
# This is the oldest version of ccache that offers support for -gsplit-dwarf
_ccache_version_min = parse_version("3.2.3")
def exists(env):
"""Look for a viable ccache implementation that meets our version requirements."""
if not env.subst("$CCACHE"):
return False
ccache = env.WhereIs("$CCACHE")
if not ccache:
print(f"Error: ccache not found at {env['CCACHE']}")
return False
if 'CCACHE_VERSION' in env and env['CCACHE_VERSION'] >= _ccache_version_min:
return True
pipe = SCons.Action._subproc(
env,
SCons.Util.CLVar(ccache) + ["--version"],
stdin="devnull",
stderr="devnull",
stdout=subprocess.PIPE,
)
if pipe.wait() != 0:
print(f"Error: failed to execute '{env['CCACHE']}'")
return False
validated = False
for line in pipe.stdout:
line = line.decode("utf-8")
if validated:
continue # consume all data
version_banner = re.search(r"^ccache version", line)
if not version_banner:
continue
ccache_version = re.split("ccache version (.+)", line)
if len(ccache_version) < 2:
continue
ccache_version = parse_version(ccache_version[1])
if ccache_version >= _ccache_version_min:
validated = True
if validated:
env['CCACHE_VERSION'] = ccache_version
else:
print(f"Error: failed to verify ccache version >= {_ccache_version_min}, found {ccache_version}")
return validated
def generate(env):
"""Add ccache support."""
# Absoluteify
env["CCACHE"] = env.WhereIs("$CCACHE")
# Propagate CCACHE related variables into the command environment
for var, host_value in os.environ.items():
if var.startswith("CCACHE_"):
env["ENV"][var] = host_value
# SERVER-48289: Adding roll-your-own CFLAGS and CXXFLAGS can cause some very "weird" issues
# with using icecc and ccache if they turn out not to be supported by the compiler. Rather
# than try to filter each and every flag someone might try for the ones we know don't
# work, we'll just let the compiler ignore them. A better approach might be to pre-filter
# flags coming in from the environment by passing them through the appropriate *IfSupported
# method, but that's a much larger effort.
if env.ToolchainIs("clang"):
env.AppendUnique(CCFLAGS=["-Qunused-arguments"])
# Check whether icecream is requested and is a valid tool.
if "ICECC" in env:
icecream = SCons.Tool.Tool('icecream')
icecream_enabled = bool(icecream) and icecream.exists(env)
else:
icecream_enabled = False
# Set up a performant ccache configuration. Here, we don't use a second preprocessor and
# pass preprocessor arguments that deterministically expand source files so a stable
# hash can be calculated on them. This both reduces the amount of work ccache needs to
# do and increases the likelihood of a cache hit.
if env.ToolchainIs("clang"):
env["ENV"].pop("CCACHE_CPP2", None)
env["ENV"]["CCACHE_NOCPP2"] = "1"
env.AppendUnique(CCFLAGS=["-frewrite-includes"])
elif env.ToolchainIs("gcc"):
if icecream_enabled:
# Newer versions of Icecream will drop -fdirectives-only from
# preprocessor and compiler flags if it does not find a remote
# build host to build on. ccache, on the other hand, will not
# pass the flag to the compiler if CCACHE_NOCPP2=1, but it will
# pass it to the preprocessor. The combination of setting
# CCACHE_NOCPP2=1 and passing the flag can lead to build
# failures.
# See: https://jira.mongodb.org/browse/SERVER-48443
# We have an open issue with Icecream and ccache to resolve the
# cause of these build failures. Once the bug is resolved and
# the fix is deployed, we can remove this entire conditional
# branch and make it like the one for clang.
# TODO: https://github.com/icecc/icecream/issues/550
env["ENV"].pop("CCACHE_CPP2", None)
env["ENV"]["CCACHE_NOCPP2"] = "1"
else:
env["ENV"].pop("CCACHE_NOCPP2", None)
env["ENV"]["CCACHE_CPP2"] = "1"
env.AppendUnique(CCFLAGS=["-fdirectives-only"])
# Ensure ccache accounts for any extra files in use that affects the generated object
# file. This can be used for situations where a file is passed as an argument to a
# compiler parameter and differences in the file need to be accounted for in the
# hash result to prevent erroneous cache hits.
if "CCACHE_EXTRAFILES" in env and env["CCACHE_EXTRAFILES"]:
env["ENV"]["CCACHE_EXTRAFILES"] = ":".join([
blackfile.path
for blackfile in env["CCACHE_EXTRAFILES"]
])
# Make a generator to expand to CCACHE in the case where we are
# not a conftest. We don't want to use ccache for configure tests
# because we don't want to use icecream for configure tests, but
# when icecream and ccache are combined we can't easily filter out
# configure tests for icecream since in that combination we use
# CCACHE_PREFIX to express the icecc tool, and at that point it is
# too late for us to meaningfully filter out conftests. So we just
# disable ccache for conftests entirely. Which feels safer
# somehow anyway.
def ccache_generator(target, source, env, for_signature):
if "conftest" not in str(target[0]):
return '$CCACHE'
return ''
env['CCACHE_GENERATOR'] = ccache_generator
# Add ccache to the relevant command lines. Wrap the reference to
# ccache in the $( $) pattern so that turning ccache on or off
# doesn't invalidate your build.
env["CCCOM"] = "$( $CCACHE_GENERATOR $)" + env["CCCOM"]
env["CXXCOM"] = "$( $CCACHE_GENERATOR $)" + env["CXXCOM"]
env["SHCCCOM"] = "$( $CCACHE_GENERATOR $)" + env["SHCCCOM"]
env["SHCXXCOM"] = "$( $CCACHE_GENERATOR $)" + env["SHCXXCOM"]
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