# -*- mode: python; -*-

import copy
import datetime
import imp
import os
import platform as py_platform
import re
import shlex
import shutil
import stat
import sys
import textwrap
import types
import urllib
#import urllib2

import buildscripts.utils
import buildscripts.docs
import buildscripts.lint
import buildscripts.clang_format

EnsureSConsVersion( 1, 1, 0 )

def versiontuple(v):
    return tuple(map(int, (v.split("."))))

# --- platform identification ---
#
# This needs to precede the options section so that we can only offer some options on certain
# platforms.

platform = os.sys.platform
nix = False
linux = False
darwin = False
windows = False
freebsd = False
openbsd = False
solaris = False

if "darwin" == platform:
    darwin = True
    platform = "osx" # prettier than darwin
elif platform.startswith("linux"):
    linux = True
    platform = "linux"
elif "sunos5" == platform:
    solaris = True
elif platform.startswith( "freebsd" ):
    freebsd = True
elif platform.startswith( "openbsd" ):
    openbsd = True
elif "win32" == platform:
    windows = True
else:
    print( "No special config for [" + platform + "] which probably means it won't work" )

nix = not windows

# --- options ----
use_clang = False

options = {}

def add_option( name, help, nargs, contributesToVariantDir,
                dest=None, default = None, type="string", choices=None, metavar=None, const=None ):

    if dest is None:
        dest = name

    if type == 'choice' and not metavar:
        metavar = '[' + '|'.join(choices) + ']'

    AddOption( "--" + name , 
               dest=dest,
               type=type,
               nargs=nargs,
               action="store",
               choices=choices,
               default=default,
               metavar=metavar,
               const=const,
               help=help )

    options[name] = { "help" : help ,
                      "nargs" : nargs ,
                      "contributesToVariantDir" : contributesToVariantDir ,
                      "dest" : dest,
                      "default": default }

def get_option( name ):
    return GetOption( name )

def has_option( name ):
    x = get_option( name )
    if x is None:
        return False

    if x == False:
        return False

    if x == "":
        return False

    return True

def get_variant_dir():

    build_dir = get_option('build-dir').rstrip('/')

    if has_option('variant-dir'):
        return (build_dir + '/' + get_option('variant-dir')).rstrip('/')

    substitute = lambda x: re.sub( "[:,\\\\/]" , "_" , x )

    a = []

    for name in options:
        o = options[name]
        if not has_option( o["dest"] ):
            continue
        if not o["contributesToVariantDir"]:
            continue
        if get_option(o["dest"]) == o["default"]:
            continue

        if o["nargs"] == 0:
            a.append( name )
        else:
            x = substitute( get_option( name ) )
            a.append( name + "_" + x )

    extras = []
    if has_option("extra-variant-dirs"):
        extras = [substitute(x) for x in get_option( 'extra-variant-dirs' ).split( ',' )]

    if has_option("add-branch-to-variant-dir"):
        extras += ["branch_" + substitute( buildscripts.utils.getGitBranch() )]

    if has_option('cache'):
        s = "cached"
        s += "/".join(extras) + "/"
    else:
        s = "${PYSYSPLATFORM}/"
        a += extras

        if len(a) > 0:
            a.sort()
            s += "/".join( a ) + "/"
        else:
            s += "normal/"

    return (build_dir + '/' + s).rstrip('/')

# build output
add_option( "mute" , "do not display commandlines for compiling and linking, to reduce screen noise", 0, False )

# installation/packaging
add_option( "prefix" , "installation prefix" , 1 , False, default='$BUILD_DIR/install' )
add_option( "extra-variant-dirs", "extra variant dir components, separated by commas", 1, False)
add_option( "add-branch-to-variant-dir", "add current git branch to the variant dir", 0, False )
add_option( "build-dir", "build output directory", 1, False, default='#build')
add_option( "variant-dir", "override variant subdirectory", 1, False )

add_option( "sharedclient", "build a libmongoclient.so/.dll" , 0 , False )

# linking options
add_option( "release" , "release build" , 0 , True )
add_option( "lto", "enable link time optimizations (experimental, except with MSVC)" , 0 , True )
add_option( "dynamic-windows", "dynamically link on Windows", 0, True)
add_option( "dynamic-boost", "dynamically link boost libraries on Windows", "?", True,
            type="choice", choices=["on", "off", "auto"], default="auto", const="on" )
add_option( "disable-declspec-thread", "don't use __declspec(thread) on Windows", 0, True)

# base compile flags
add_option( "64" , "whether to force 64 bit" , 0 , True , "force64" )
add_option( "32" , "whether to force 32 bit" , 0 , True , "force32" )

add_option( "endian" , "endianness of target platform" , 1 , False , "endian",
            type="choice", choices=["big", "little", "auto"], default="auto" )

add_option( "cxx", "compiler to use" , 1 , True )
add_option( "cc", "compiler to use for c" , 1 , True )
add_option( "cc-use-shell-environment", "use $CC from shell for C compiler" , 0 , False )
add_option( "cxx-use-shell-environment", "use $CXX from shell for C++ compiler" , 0 , False )
add_option( "c++11", "enable c++11 support (experimental)", "?", True,
            type="choice", choices=["on", "off", "auto"], const="on", default="off" )

add_option( "cpppath", "Include path if you have headers in a nonstandard directory" , 1 , False )
add_option( "libpath", "Library path if you have libraries in a nonstandard directory" , 1 , False )

add_option( "extrapath", "comma separated list of add'l paths  (--extrapath /opt/foo/,/foo) static linking" , 1 , False )
add_option( "extralib", "comma separated list of libraries  (--extralib js_static,readline" , 1 , False )

add_option("runtime-library-search-path",
           "comma separated list of dirs to append to PATH to find dynamic libs at runtime",
           1, False)

add_option( "ssl" , "Enable SSL" , 0 , True )

# library choices
add_option( "libc++", "use libc++ (experimental, requires clang)", 0, True )

# new style debug and optimize flags
add_option( "dbg", "Enable runtime debugging checks", "?", True, "dbg",
            type="choice", choices=["on", "off"], const="on" )

add_option( "opt", "Enable compile-time optimization", "?", True, "opt",
            type="choice", choices=["on", "off"], const="on" )

add_option( "sanitize", "enable selected sanitizers", 1, True, metavar="san1,san2,...sanN" )
add_option( "llvm-symbolizer", "name of (or path to) the LLVM symbolizer", 1, False, default="llvm-symbolizer" )

add_option( "gcov" , "compile with flags for gcov" , 0 , True )

add_option("use-sasl-client", "Support SASL authentication in the client library", 0, False)

add_option('build-fast-and-loose', "NEVER for production builds", 0, False)

add_option( "boost-lib-search-suffixes",
            "Comma delimited sequence of boost library suffixes to search",
            1, False )

add_option('disable-warnings-as-errors', "Don't add -Werror to compiler command line", 0, False)

add_option('propagate-shell-environment',
           "Pass shell environment to sub-processes (NEVER for production builds)",
           0, False)

add_option('gtest-filter', "Pass argument as filter to gtest", 1, False)

add_option('mongo-orchestration-preset',
           "Pass argument to mongo-orchestration as the configuration preset",
           1, False, default='basic.json' )

add_option('mongo-orchestration-host',
           "Host mongo-orchestration is running on",
           1, False, default='localhost' )

add_option('mongo-orchestration-port',
           "Host mongo-orchestration is running on",
           1, False, default='8889' )

add_option('variables-help',
           "Print the help text for SCons variables", 0, False)

if darwin:
    add_option("osx-version-min", "minimum OS X version to support", 1, True)

elif windows:
    win_version_min_choices = {
        'xpsp3'   : ('0501', '0300'),
        'ws03sp2' : ('0502', '0200'),
        'vista'   : ('0600', '0000'),
        'ws08r2'  : ('0601', '0000'),
        'win7'    : ('0601', '0000'),
        'win8'    : ('0602', '0000'),
    }

    add_option("win-version-min", "minimum Windows version to support", 1, True,
               type = 'choice', default = None,
               choices = win_version_min_choices.keys())

    # Someday get rid of --32 and --64 for windows and use these with a --msvc-target-arch flag
    # that mirrors msvc-host-arch.
    msvc_arch_choices = ['x86', 'i386', 'amd64', 'emt64', 'x86_64', 'ia64']

    add_option("msvc-host-arch", "host architecture for ms toolchain", 1, True,
               type="choice", choices=msvc_arch_choices)

    add_option("msvc-script",
               "msvc toolchain setup script, pass no argument to suppress script execution",
               1, True)

    add_option("msvc-version", "select msvc version", 1, True)

add_option('cache',
           "Use an object cache rather than a per-build variant directory (experimental)",
           0, False)

add_option('cache-dir',
           "Specify the directory to use for caching objects if --cache is in use",
           1, False, default="$BUILD_DIR/scons/cache")

variable_parse_mode_choices=['auto', 'posix', 'other']
add_option('variable-parse-mode',
           "Select which parsing mode is used to interpret command line variables",
           1, False,
           type='choice', default=variable_parse_mode_choices[0],
           choices=variable_parse_mode_choices)

# Setup the command-line variables
def variable_shlex_converter(val):
    parse_mode = get_option('variable-parse-mode')
    if parse_mode == 'auto':
        parse_mode = 'other' if windows else 'posix'
    return shlex.split(val, posix=(parse_mode == 'posix'))

env_vars = Variables()

env_vars.Add('ARFLAGS',
    help='Sets flags for the archiver',
    converter=variable_shlex_converter)

env_vars.Add('CCFLAGS',
    help='Sets flags for the C and C++ compiler',
    converter=variable_shlex_converter)

env_vars.Add('CFLAGS',
    help='Sets flags for the C compiler',
    converter=variable_shlex_converter)

env_vars.Add('CPPDEFINES',
    help='Sets pre-processor definitions for C and C++',
    converter=variable_shlex_converter)

env_vars.Add('CPPPATH',
    help='Adds paths to the preprocessor search path',
    converter=variable_shlex_converter)

env_vars.Add('CXXFLAGS',
    help='Sets flags for the C++ compiler',
    converter=variable_shlex_converter)

env_vars.Add('LIBPATH',
    help='Adds paths to the linker search path',
    converter=variable_shlex_converter)

env_vars.Add('LIBS',
    help='Adds extra libraries to link against',
    converter=variable_shlex_converter)

env_vars.Add('LINKFLAGS',
    help='Sets flags for the linker',
    converter=variable_shlex_converter)

env_vars.Add('RPATH',
    help='Set the RPATH for dynamic libraries and executables',
    converter=variable_shlex_converter)

env_vars.Add('SHCCFLAGS',
    help='Sets flags for the C and C++ compiler when building shared libraries',
    converter=variable_shlex_converter)

env_vars.Add('SHCFLAGS',
    help='Sets flags for the C compiler when building shared libraries',
    converter=variable_shlex_converter)

env_vars.Add('SHCXXFLAGS',
    help='Sets flags for the C++ compiler when building shared libraries',
    converter=variable_shlex_converter)

env_vars.Add('SHLINKFLAGS',
    help='Sets flags for the linker when building shared libraries',
    converter=variable_shlex_converter)

# don't run configure if user calls --help
if GetOption('help'):
    Return()

# --- environment setup ---

# If the user isn't using the # to indicate top-of-tree or $ to expand a variable, forbid
# relative paths. Relative paths don't really work as expected, because they end up relative to
# the top level SConstruct, not the invokers CWD. We could in theory fix this with
# GetLaunchDir, but that seems a step too far.
buildDir = get_option('build-dir').rstrip('/')
if buildDir[0] not in ['$', '#']:
    if not os.path.isabs(buildDir):
        print("Do not use relative paths with --build-dir")
        Exit(1)

cacheDir = get_option('cache-dir').rstrip('/')
if cacheDir[0] not in ['$', '#']:
    if not os.path.isabs(cacheDir):
        print("Do not use relative paths with --cache-dir")
        Exit(1)

installDir = get_option('prefix').rstrip('/')
if installDir[0] not in ['$', '#']:
    if not os.path.isabs(installDir):
        print("Do not use relative paths with --prefix")
        Exit(1)

sconsDataDir = Dir(buildDir).Dir('scons')
SConsignFile(str(sconsDataDir.File('sconsign')))

def printLocalInfo():
    import sys, SCons
    print( "scons version: " + SCons.__version__ )
    print( "python version: " + " ".join( [ str(i) for i in sys.version_info ] ) )

printLocalInfo()

boostLibs = [ "thread" , "system" ]

linux64  = False
force32 = has_option( "force32" ) 
force64 = has_option( "force64" )
if not force64 and not force32 and os.getcwd().endswith( "mongo-64" ):
    force64 = True
    print( "*** assuming you want a 64-bit build b/c of directory *** " )
msarch = None
if force32:
    msarch = "x86"
elif force64:
    msarch = "amd64"

releaseBuild = has_option("release")

# validate debug and optimization options
dbg_opt_mapping = {
    # --dbg, --opt   :   dbg    opt
    ( None,  None  ) : ( False, True ),
    ( None,  "on"  ) : ( False, True ),
    ( None,  "off" ) : ( False, False ),
    ( "on",  None  ) : ( True,  False ),  # special case interaction
    ( "on",  "on"  ) : ( True,  True ),
    ( "on",  "off" ) : ( True,  False ),
    ( "off", None  ) : ( False, True ),
    ( "off", "on"  ) : ( False, True ),
    ( "off", "off" ) : ( False, False ),
}
debugBuild, optBuild = dbg_opt_mapping[(get_option('dbg'), get_option('opt'))]

if releaseBuild and (debugBuild or not optBuild):
    print("Error: A --release build may not have debugging, and must have optimization")
    Exit(1)

mongoclientVersion = "1.1.3"
# We don't keep the -pre in the user testable version identifiers, because
# nobody should be conditioning on the pre-release status.
mongoclientVersionComponents = re.split(r'\.|-rc', mongoclientVersion.partition('-pre')[0])
if len(mongoclientVersionComponents) not in (3,4):
    print("Error: client version most be of the form w.x.y[-rcz][-string]")
    Exit(1)

# The Scons 'default' tool enables a lot of tools that we don't actually need to enable.
# On platforms like Solaris, it actually does the wrong thing by enabling the sunstudio
# toolchain first. As such it is simpler and more efficient to manually load the precise
# set of tools we need for each platform.
# If we aren't on a platform where we know the minimal set of tools, we fallback to loading
# the 'default' tool.
def decide_platform_tools():
    if windows:
        # we only support MS toolchain on windows
        return ['msvc', 'mslink', 'mslib']
    elif linux:
        return ['gcc', 'g++', 'gnulink', 'ar']
    elif solaris:
        return ['gcc', 'g++', 'gnulink', 'ar']
    elif darwin:
        return ['gcc', 'g++', 'applelink', 'ar']
    else:
        return ["default"]

tools = decide_platform_tools() + ["unittest", "integration_test", "textfile"]

# We defer building the env until we have determined whether we want certain values. Some values
# in the env actually have semantics for 'None' that differ from being absent, so it is better
# to build it up via a dict, and then construct the Environment in one shot with kwargs.
envDict = dict(BUILD_DIR=buildDir,
               VARIANT_DIR=get_variant_dir(),
               EXTRAPATH=get_option("extrapath"),
               PYTHON=File(buildscripts.utils.find_python()),
               tools=tools,
               PYSYSPLATFORM=os.sys.platform,
               CONFIGUREDIR=sconsDataDir.Dir('sconf_temp'),
               CONFIGURELOG=sconsDataDir.File('config.log'),
               MONGOCLIENT_VERSION=mongoclientVersion,
               MONGOCLIENT_VERSION_MAJOR=mongoclientVersionComponents[0],
               MONGOCLIENT_VERSION_MINOR=mongoclientVersionComponents[1],
               MONGOCLIENT_VERSION_PATCH=mongoclientVersionComponents[2],
               INSTALL_DIR=installDir,
               )

if windows:
    if msarch:
        envDict['TARGET_ARCH'] = msarch

    # We can't set this to None without disturbing the autodetection,
    # so only set it conditionally.
    if has_option('msvc-host-arch'):
        envDict['HOST_ARCH'] = get_option('msvc-host-arch')

    msvc_version = get_option('msvc-version')
    msvc_script = get_option('msvc-script')

    if msvc_version:
        if msvc_script:
            print("Passing --msvc-version with --msvc-script is not meaningful")
            Exit(1)
        envDict['MSVC_VERSION'] = msvc_version

    # The python None value is meaningful to MSVC_USE_SCRIPT; we want to interpret
    # --msvc-script= with no argument as meaning 'None', so check explicitly against None so
    # that '' is not interpreted as false.
    if msvc_script is not None:
        if has_option('msvc-host-arch'):
            print("Passing --msvc-host-arch with --msvc-script is not meaningful")
            Exit(1)
        if msarch:
            print("Passing --32 or --64 with --msvc-script is not meaningful")
            Exit(1)
        if msvc_script == "":
            msvc_script = None
        envDict['MSVC_USE_SCRIPT'] = msvc_script

env = Environment(variables=env_vars, **envDict)
del envDict

def fatal_error(env, msg, *args):
    print (msg.format(*args))
    Exit(1)

def conf_error(env, msg, *args):
    print (msg.format(*args))
    print ("See {0} for details".format(env['CONFIGURELOG'].abspath))

    Exit(1)

env.AddMethod(fatal_error, 'FatalError')
env.AddMethod(conf_error, 'ConfError')

if has_option('variables-help'):
    print (env_vars.GenerateHelpText(env))
    Exit(0)

unknown_vars = env_vars.UnknownVariables()
if unknown_vars:
    env.FatalError("Unknown variables specified: {0}", ", ".join(unknown_vars.keys()))


# Add any scons options that conflict with scons variables here.
# The first item in each tuple is the option name and the second
# is the variable name
variable_conflicts = [
    ('libpath', 'LIBPATH'),
    ('cpppath', 'CPPPATH'),
    ('extrapath', 'CPPPATH'),
    ('extrapath', 'LIBPATH'),
    ('extralib', 'LIBS')
]

for (opt_name, var_name) in variable_conflicts:
    if has_option(opt_name) and var_name in env:
        env.FatalError("Both option \"--{0}\" and variable {1} were specified", opt_name, var_name)

if has_option("cache"):
    EnsureSConsVersion( 2, 3, 0 )
    if has_option("release"):
        env.FatalError(
            "Using the experimental --cache option is not permitted for --release builds")
    if has_option("gcov"):
        env.FatalError("Mixing --cache and --gcov doesn't work correctly yet. See SERVER-11084")
    env.CacheDir(str(env.Dir(cacheDir)))

if has_option("propagate-shell-environment"):
    env['ENV'] = dict(os.environ);

if has_option('runtime-library-search-path'):
    libs = get_option('runtime-library-search-path').split(',')
    envVar = None
    if windows:
        envVar = 'PATH'
    elif darwin:
        envVar = 'DYLD_LIBRARY_PATH'
    else:
        envVar = 'LD_LIBRARY_PATH'
    for lib in libs:
        env.AppendENVPath(envVar, env.Dir(lib), delete_existing=0)

# Ignore fast-and-loose option if the scons cache is enabled (see SERVER-19088)
if has_option('build-fast-and-loose') and not has_option('cache'):
    # See http://www.scons.org/wiki/GoFastButton for details
    env.Decider('MD5-timestamp')
    env.SetOption('max_drift', 1)
    env.SourceCode('.', None)

if has_option('mute'):
    env.Append( CCCOMSTR = "Compiling $TARGET" )
    env.Append( CXXCOMSTR = env["CCCOMSTR"] )
    env.Append( SHCCCOMSTR = "Compiling $TARGET" )
    env.Append( SHCXXCOMSTR = env["SHCCCOMSTR"] )
    env.Append( LINKCOMSTR = "Linking $TARGET" )
    env.Append( SHLINKCOMSTR = env["LINKCOMSTR"] )
    env.Append( ARCOMSTR = "Generating library $TARGET" )

endian = get_option( "endian" )

if endian == "auto":
    endian = sys.byteorder

if endian == "little":
    env["MONGO_BYTE_ORDER"] = "1234"
elif endian == "big":
    env["MONGO_BYTE_ORDER"] = "4321"

if env['PYSYSPLATFORM'] == 'linux3':
    env['PYSYSPLATFORM'] = 'linux2'
if 'freebsd' in env['PYSYSPLATFORM']:
    env['PYSYSPLATFORM'] = 'freebsd'

if os.sys.platform == 'win32':
    env['OS_FAMILY'] = 'win'
else:
    env['OS_FAMILY'] = 'posix'

if has_option( "cc-use-shell-environment" ) and has_option( "cc" ):
    env.FatalError("Cannot specify both --cc-use-shell-environment and --cc")
elif has_option( "cxx-use-shell-environment" ) and has_option( "cxx" ):
    env.FatalError("Cannot specify both --cxx-use-shell-environment and --cxx")


if has_option( "gtest-filter" ):
    env["gtest_filter"] = get_option('gtest-filter')

if has_option( "cxx-use-shell-environment" ):
    env["CXX"] = os.getenv("CXX");
    env["CC"] = env["CXX"]
if has_option( "cc-use-shell-environment" ):
    env["CC"] = os.getenv("CC");

if has_option( "cxx" ):
    if not has_option( "cc" ):
        env.FatalError("Must specify C compiler when specifying C++ compiler")
    env["CXX"] = get_option( "cxx" )
if has_option( "cc" ):
    if not has_option( "cxx" ):
        env.FatalError("Must specify C++ compiler when specifying C compiler")
    env["CC"] = get_option( "cc" )

if has_option( "libpath" ):
    env["LIBPATH"] = [get_option( "libpath" )]

if has_option( "cpppath" ):
    env["CPPPATH"] = [get_option( "cpppath" )]

env.Prepend(
    CPPDEFINES=[
        "MONGO_EXPOSE_MACROS" ,
    ],
    CPPPATH=[
        '$VARIANT_DIR',
        '$VARIANT_DIR/mongo'
    ]
)

extraLibPlaces = []

env['EXTRACPPPATH'] = []
env['EXTRALIBPATH'] = []

def addExtraLibs( s ):
    for x in s.split(","):
        env.Append( EXTRACPPPATH=[ x + "/include" ] )
        env.Append( EXTRALIBPATH=[ x + "/lib" ] )
        extraLibPlaces.append( x + "/lib" )

if has_option( "extrapath" ):
    addExtraLibs( GetOption( "extrapath" ) )

if has_option( "extralib" ):
    for x in GetOption( "extralib" ).split( "," ):
        env.Append( LIBS=[ x ] )

# ---- other build setup -----

if "uname" in dir(os):
    processor = os.uname()[4]
else:
    processor = "i386"

if force32:
    processor = "i386"
if force64:
    processor = "x86_64"

env['PROCESSOR_ARCHITECTURE'] = processor

nixLibPrefix = "lib"

if darwin:
    pass
elif linux:

    env.Append( LIBS=['m'] )
    
    if 'mips' in os.uname()[4] and '32bit' in py_platform.architecture():
        env.Append( LIBS=['atomic'] )
	
    if os.uname()[4] == "x86_64" and not force32:
        linux64 = True
        nixLibPrefix = "lib64"
        env.Append( EXTRALIBPATH=["/usr/lib64" , "/lib64" ] )
        env.Append( LIBS=["pthread"] )

        force64 = False

    if force32:
        env.Append( EXTRALIBPATH=["/usr/lib32"] )

elif solaris:
     env.Append( CPPDEFINES=[ "__sunos__" ] )
     env.Append( LIBS=["socket","resolv"] )

elif freebsd:
    env.Append( LIBS=[ "kvm" ] )
    env.Append( EXTRACPPPATH=[ "/usr/local/include" ] )
    env.Append( EXTRALIBPATH=[ "/usr/local/lib" ] )
    env.Append( CPPDEFINES=[ "__freebsd__" ] )
    env.Append( CCFLAGS=[ "-fno-omit-frame-pointer" ] )

elif openbsd:
    env.Append( EXTRACPPPATH=[ "/usr/local/include" ] )
    env.Append( EXTRALIBPATH=[ "/usr/local/lib" ] )
    env.Append( CPPDEFINES=[ "__openbsd__" ] )

elif windows:
    dynamicCRT = has_option("dynamic-windows")

    # Unless otherwise specified, link boost in the same manner as the CRT.
    dynamicBoost = get_option("dynamic-boost")
    if dynamicBoost == "auto":
        dynamicBoost = "on" if dynamicCRT else "off"
    if dynamicBoost == "on":
        env.Append( CPPDEFINES=[ "BOOST_ALL_DYN_LINK" ] )

    if has_option("sharedclient") and not dynamicCRT:
        env.FatalError("The shared client must be built with the dynamic runtime library")

    # If tools configuration fails to set up 'cl' in the path, fall back to importing the whole
    # shell environment and hope for the best. This will work, for instance, if you have loaded
    # an SDK shell.
    for pathdir in env['ENV']['PATH'].split(os.pathsep):
        if os.path.exists(os.path.join(pathdir, 'cl.exe')):
            break
    else:
        print("NOTE: Tool configuration did not find 'cl' compiler, falling back to os environment")
        env['ENV'] = dict(os.environ)

    env.Append( CPPDEFINES=[ "_UNICODE" ] )
    env.Append( CPPDEFINES=[ "UNICODE" ] )
    env.Append( CPPDEFINES=[ "NOMINMAX" ] )

    # /EHsc exception handling style for visual studio
    # /W3 warning level
    env.Append(CCFLAGS=["/EHsc","/W3"])

    # some warnings we don't like:
    env.Append(CCFLAGS=[

        # 'conversion' conversion from 'type1' to 'type2', possible loss of data
        #     An integer type is converted to a smaller integer type.
        "/wd4244",

        # 'identifier' : class 'type' needs to have dll-interface to be used by clients of class 'type2'
        #     Typically some STL type isn't dllexport adorned, and we can't do anything about that
        "/wd4251",

        # 'var' : conversion from 'size_t' to 'type', possible loss of data When compiling with
        # /Wp64, or when compiling on a 64-bit operating system, type is 32 bits but size_t is
        # 64 bits when compiling for 64-bit targets. To fix this warning, use size_t instead of
        # a type
        "/wd4267",

        # non - DLL-interface classkey 'identifier' used as base for DLL-interface classkey 'identifier'
        #    Typically some base like noncopyable isn't dllexport adorned; nothing we can do
        "/wd4275",

        # C++ exception specification ignored except to indicate a function is not
        # __declspec(nothrow A function is declared using exception specification, which Visual
        # C++ accepts but does not implement
        "/wd4290",

        # 'this' : used in base member initializer list
        #    The this pointer is valid only within nonstatic member functions. It cannot be
        #    used in the initializer list for a base class.
        "/wd4355",

        # 'type' : forcing value to bool 'true' or 'false' (performance warning)
        #    This warning is generated when a value that is not bool is assigned or coerced
        #    into type bool.
        "/wd4800",

        # unknown pragma -- added so that we can specify unknown pragmas for other compilers
        "/wd4068",

        # On extremely old versions of MSVC (pre 2k5), default constructing an array member in a
        # constructor's initialization list would not zero the array members "in some cases".
        # since we don't target MSVC versions that old, this warning is safe to ignore.
        "/wd4351",
    ])

    if not has_option("disable-warnings-as-errors"):
        env.Append(
            CCFLAGS=["/WX"],
            LINKFLAGS=["/WX"],
        )

    env.Append( CPPDEFINES=[
        "_CONSOLE",
        "_CRT_NONSTDC_NO_WARNINGS",
        "_CRT_SECURE_NO_WARNINGS",
        "_CRT_SECURE_NO_DEPRECATE",
        "_SCL_SECURE_NO_WARNINGS",
        "_SCL_SECURE_NO_DEPRECATE",
    ] )

    # this would be for pre-compiled headers, could play with it later  
    #env.Append( CCFLAGS=['/Yu"pch.h"'] )

    # docs say don't use /FD from command line (minimal rebuild)
    # /Gy function level linking (implicit when using /Z7)
    # /Z7 debug info goes into each individual .obj file -- no .pdb created 
    env.Append( CCFLAGS= ["/Z7", "/errorReport:none"] )

    # /DEBUG will tell the linker to create a .pdb file
    # which WinDbg and Visual Studio will use to resolve
    # symbols if you want to debug a release-mode image.
    # Note that this means we can't do parallel links in the build.
    #
    # Please also note that this has nothing to do with _DEBUG or optimization.
    env.Append( LINKFLAGS=["/DEBUG"] )

    # /MD:  use the multithreaded, DLL version of the run-time library (MSVCRT.lib/MSVCR###.DLL)
    # /MT:  use the multithreaded, static version of the run-time library (LIBCMT.lib)
    # /MDd: Defines _DEBUG, _MT, _DLL, and uses MSVCRTD.lib/MSVCRD###.DLL
    # /MTd: Defines _DEBUG, _MT, and causes your application to use the
    #       debug multithread version of the run-time library (LIBCMTD.lib)

    winRuntimeLibMap = {
          #dyn   #dbg
        ( False, False ) : "/MT",
        ( False, True  ) : "/MTd",
        ( True,  False ) : "/MD",
        ( True,  True  ) : "/MDd",
    }

    env.Append(CCFLAGS=[winRuntimeLibMap[(dynamicCRT, debugBuild)]])

    # With VS 2012 and later we need to specify 5.01 as the target console
    # so that our 32-bit builds run on Windows XP
    # See https://software.intel.com/en-us/articles/linking-applications-using-visual-studio-2012-to-run-on-windows-xp
    #
    if msarch == "x86":
        env.Append( LINKFLAGS=["/SUBSYSTEM:CONSOLE,5.01"])

    if optBuild:
        # /O2:  optimize for speed (as opposed to size)
        # /Oy-: disable frame pointer optimization (overrides /O2, only affects 32-bit)
        # /INCREMENTAL: NO - disable incremental link - avoid the level of indirection for function
        # calls
        env.Append( CCFLAGS=["/O2", "/Oy-"] )
        env.Append( LINKFLAGS=["/INCREMENTAL:NO"])
    else:
        env.Append( CCFLAGS=["/Od"] )

    if debugBuild and not optBuild:
        # /RTC1: - Enable Stack Frame Run-Time Error Checking; Reports when a variable is used
        # without having been initialized (implies /Od: no optimizations)
        env.Append( CCFLAGS=["/RTC1"] )

    env.Append(LIBS=[ 'ws2_32.lib', 'DbgHelp.lib' ])

if nix:

    # -Winvalid-pch Warn if a precompiled header (see Precompiled Headers) is found in the search path but can't be used.
    env.Append( CCFLAGS=["-fPIC",
                         "-ggdb",
                         "-pthread",
                         "-Wall",
                         "-Wsign-compare",
                         "-Wno-unknown-pragmas",
                         "-Winvalid-pch"] )
    # env.Append( " -Wconversion" ) TODO: this doesn't really work yet
    if linux or darwin:
        env.Append( CCFLAGS=["-pipe"] )
        if not has_option("disable-warnings-as-errors"):
            env.Append( CCFLAGS=["-Werror"] )

    env.Append( CPPDEFINES=["_FILE_OFFSET_BITS=64"] )
    env.Append( CXXFLAGS=["-Wnon-virtual-dtor", "-Woverloaded-virtual"] )
    env.Append( LINKFLAGS=["-fPIC"] )

    # SERVER-9761: Ensure early detection of missing symbols in dependent libraries at program
    # startup.
    #
    # TODO: Is it necessary to add to both linkflags and shlinkflags, or are LINKFLAGS
    # propagated to SHLINKFLAGS?
    if darwin:
        env.Append( LINKFLAGS=["-Wl,-bind_at_load"] )
        env.Append( SHLINKFLAGS=["-Wl,-bind_at_load"] )
    else:
        env.Append( LINKFLAGS=["-Wl,-z,now"] )
        env.Append( SHLINKFLAGS=["-Wl,-z,now"] )

    if not darwin:
        env.Append( LINKFLAGS=["-rdynamic"] )

    env.Append( LIBS=[] )

    # Allow colorized output
    env['ENV']['TERM'] = os.environ.get('TERM', None)

    if linux and has_option( "gcov" ):
        env.Append( CXXFLAGS=" -fprofile-arcs -ftest-coverage " )
        env.Append( LINKFLAGS=" -fprofile-arcs -ftest-coverage " )

    if optBuild:
        env.Append( CCFLAGS=["-O3"] )
    else:
        env.Append( CCFLAGS=["-O0"] )

    if debugBuild:
        if not optBuild:
            env.Append( CCFLAGS=["-fstack-protector"] )
            env.Append( LINKFLAGS=["-fstack-protector"] )
            env.Append( SHLINKFLAGS=["-fstack-protector"] )

    if force64:
        env.Append( CCFLAGS="-m64" )
        env.Append( LINKFLAGS="-m64" )

    if force32:
        env.Append( CCFLAGS="-m32" )
        env.Append( LINKFLAGS="-m32" )

if debugBuild:
    env.Append( CPPDEFINES=["MONGO_DEBUG_BUILD"] );

try:
    umask = os.umask(0o22)
except OSError:
    pass

conf = Configure(env)
if not conf.CheckCXXHeader('gtest/gtest.h'):
    env.Prepend(CPPPATH=['$VARIANT_DIR/third_party/gtest-1.7.0/include'])
env = conf.Finish()

boostSuffixList = ["-mt", ""]
if get_option("boost-lib-search-suffixes") is not None:
    boostSuffixList = get_option("boost-lib-search-suffixes")
    if boostSuffixList == "":
        boostSuffixList = []
    else:
        boostSuffixList = boostSuffixList.split(',')

env.Append( CPPPATH=['$EXTRACPPPATH'],
            LIBPATH=['$EXTRALIBPATH'] )

# --- check system ---

def doConfigure(myenv):

    # Check that the compilers work.
    #
    # TODO: Currently, we have some flags already injected. Eventually, this should test the
    # bare compilers, and we should re-check at the very end that TryCompile and TryLink still
    # work with the flags we have selected.
    conf = Configure(myenv, help=False)

    if 'CheckCXX' in dir( conf ):
        if not conf.CheckCXX():
            conf.env.FatalError("C++ compiler {0} does not work", conf.env["CXX"])

    # Only do C checks if CC != CXX
    check_c = (myenv["CC"] != myenv["CXX"])

    if check_c and 'CheckCC' in dir( conf ):
        if not conf.CheckCC():
            conf.env.FatalError("C compiler {0} does not work", conf.env["CC"])
    myenv = conf.Finish()

    # Identify the toolchain in use. We currently support the following:
    # TODO: Goes in the env?
    toolchain_gcc = "GCC"
    toolchain_clang = "clang"
    toolchain_msvc = "MSVC"

    def CheckForToolchain(context, toolchain, lang_name, compiler_var, source_suffix):
        test_bodies = {
            toolchain_gcc : (
                # Clang also defines __GNUC__
                """
                #if !defined(__GNUC__) || defined(__clang__)
                #error
                #endif
                """),
            toolchain_clang : (
                """
                #if !defined(__clang__)
                #error
                #endif
                """),
            toolchain_msvc : (
                """
                #if !defined(_MSC_VER)
                #error
                #endif
                """),
        }
        print_tuple = (lang_name, context.env[compiler_var], toolchain)
        context.Message('Checking if %s compiler "%s" is %s... ' % print_tuple)
        # Strip indentation from the test body to ensure that the newline at the end of the
        # endif is the last character in the file (rather than a line of spaces with no
        # newline), and that all of the preprocessor directives start at column zero. Both of
        # these issues can trip up older toolchains.
        test_body = textwrap.dedent(test_bodies[toolchain])
        result = context.TryCompile(test_body, source_suffix)
        context.Result(result)
        return result

    conf = Configure(myenv, help=False, custom_tests = {
        'CheckForToolchain' : CheckForToolchain,
    })

    toolchain = None
    have_toolchain = lambda: toolchain != None
    using_msvc = lambda: toolchain == toolchain_msvc
    using_gcc = lambda: toolchain == toolchain_gcc
    using_clang = lambda: toolchain == toolchain_clang

    if windows:
        toolchain_search_sequence = [toolchain_msvc]
    else:
        toolchain_search_sequence = [toolchain_gcc, toolchain_clang]

    for candidate_toolchain in toolchain_search_sequence:
        if conf.CheckForToolchain(candidate_toolchain, "C++", "CXX", ".cpp"):
            toolchain = candidate_toolchain
            break

    if not have_toolchain():
        conf.env.FatalError("Couldn't identify the toolchain")

    if check_c and not conf.CheckForToolchain(toolchain, "C", "CC", ".c"):
        conf.env.FatalError("C toolchain doesn't match identified C++ toolchain")

    myenv = conf.Finish()

    global use_clang
    use_clang = using_clang()

    if using_gcc():
        myenv.Append(LINKFLAGS=["-pthread"])

    # Figure out what our minimum windows version is. If the user has specified, then use
    # that. Otherwise, if they have explicitly selected between 32 bit or 64 bit, choose XP or
    # Vista respectively. Finally, if they haven't done either of these, try invoking the
    # compiler to figure out whether we are doing a 32 or 64 bit build and select as
    # appropriate.
    if windows:
        win_version_min = None
        default_32_bit_min = 'xpsp3'
        default_64_bit_min = 'ws03sp2'
        if has_option('win-version-min'):
            win_version_min = get_option('win-version-min')
        else:
            if force32:
                win_version_min = default_32_bit_min
            elif force64:
                win_version_min = default_64_bit_min
            else:
                def CheckFor64Bit(context):
                    win64_test_body = textwrap.dedent(
                        """
                        #if !defined(_WIN64)
                        #error
                        #endif
                        """
                    )
                    context.Message('Checking if toolchain is in 64-bit mode... ')
                    result = context.TryCompile(win64_test_body, ".c")
                    context.Result(result)
                    return result

                conf = Configure(myenv, help=False, custom_tests = {
                    'CheckFor64Bit' : CheckFor64Bit
                })
                if conf.CheckFor64Bit():
                    win_version_min = default_64_bit_min
                else:
                    win_version_min = default_32_bit_min
                conf.Finish();

        env['WIN_VERSION_MIN'] = win_version_min
        win_version_min = win_version_min_choices[win_version_min]
        env.Append( CPPDEFINES=[("_WIN32_WINNT", "0x" + win_version_min[0])] )
        env.Append( CPPDEFINES=[("NTDDI_VERSION", "0x" + win_version_min[0] + win_version_min[1])] )

    def AddFlagIfSupported(env, tool, extension, flag, **mutation):
        def CheckFlagTest(context, tool, extension, flag):
            test_body = ""
            context.Message('Checking if %s compiler supports %s... ' % (tool, flag))
            ret = context.TryCompile(test_body, extension)
            context.Result(ret)
            return ret

        if using_msvc():
            env.FatalError("AddFlagIfSupported is not currently supported with MSVC")

        test_mutation = mutation
        if using_gcc():
            test_mutation = copy.deepcopy(mutation)
            # GCC helpfully doesn't issue a diagnostic on unknown flags of the form -Wno-xxx
            # unless other diagnostics are triggered. That makes it tough to check for support
            # for -Wno-xxx. To work around, if we see that we are testing for a flag of the
            # form -Wno-xxx (but not -Wno-error=xxx), we also add -Wxxx to the flags. GCC does
            # warn on unknown -Wxxx style flags, so this lets us probe for availablity of
            # -Wno-xxx.
            for kw in test_mutation.keys():
                test_flags = test_mutation[kw]
                for test_flag in test_flags:
                    if test_flag.startswith("-Wno-") and not test_flag.startswith("-Wno-error="):
                        test_flags.append(re.sub("^-Wno-", "-W", test_flag))

        cloned = env.Clone()
        cloned.Append(**test_mutation)

        # For GCC, we don't need anything since bad flags are already errors, but
        # adding -Werror won't hurt. For clang, bad flags are only warnings, so we need -Werror
        # to make them real errors.
        cloned.Append(CCFLAGS=['-Werror'])
        conf = Configure(cloned, help=False, custom_tests = {
                'CheckFlag' : lambda ctx  : CheckFlagTest(ctx, tool, extension, flag)
        })
        available = conf.CheckFlag()
        conf.Finish()
        if available:
            env.Append(**mutation)
        return available

    def AddToCFLAGSIfSupported(env, flag):
        return AddFlagIfSupported(env, 'C', '.c', flag, CFLAGS=[flag])

    def AddToCCFLAGSIfSupported(env, flag):
        return AddFlagIfSupported(env, 'C', '.c', flag, CCFLAGS=[flag])

    def AddToCXXFLAGSIfSupported(env, flag):
        return AddFlagIfSupported(env, 'C++', '.cpp', flag, CXXFLAGS=[flag])

    if using_gcc() or using_clang():
        # This warning was added in g++-4.8.
        AddToCCFLAGSIfSupported(myenv, '-Wno-unused-local-typedefs')

        # Clang likes to warn about unused functions, which seems a tad aggressive and breaks
        # -Werror, which we want to be able to use.
        AddToCCFLAGSIfSupported(myenv, '-Wno-unused-function')

        # TODO: Note that the following two flags are added to CCFLAGS even though they are
        # really C++ specific. We need to do this because SCons passes CXXFLAGS *before*
        # CCFLAGS, but CCFLAGS contains -Wall, which re-enables the warnings we are trying to
        # suppress. In the future, we should move all warning flags to CCWARNFLAGS and
        # CXXWARNFLAGS and add these to CCOM and CXXCOM as appropriate.
        #
        # Clang likes to warn about unused private fields, but some of our third_party
        # libraries have such things.
        AddToCCFLAGSIfSupported(myenv, '-Wno-unused-private-field')

        # Prevents warning about using deprecated features (such as auto_ptr in c++11)
        # Using -Wno-error=deprecated-declarations does not seem to work on some compilers,
        # including at least g++-4.6.
        AddToCCFLAGSIfSupported(myenv, "-Wno-deprecated-declarations")

        # As of clang-3.4, this warning appears in v8, and gets escalated to an error.
        AddToCCFLAGSIfSupported(myenv, "-Wno-tautological-constant-out-of-range-compare")

        # New in clang-3.4, trips up things mostly in third_party, but in a few places in the
        # primary mongo sources as well.
        AddToCCFLAGSIfSupported(myenv, "-Wno-unused-const-variable")

        # This has been suppressed in gcc 4.8, due to false positives, but not in clang.  So
        # we explicitly disable it here.
        AddToCCFLAGSIfSupported(myenv, "-Wno-missing-braces")

    # Check if we need to disable null-conversion warnings
    if using_clang():
        def CheckNullConversion(context):

            test_body = """
            #include <boost/shared_ptr.hpp>
            struct TestType { int value; bool boolValue; };
            bool foo() {
                boost::shared_ptr<TestType> sp(new TestType);
                return NULL != sp;
            }
            """

            context.Message('Checking if implicit boost::shared_ptr null conversion is supported... ')
            ret = context.TryCompile(textwrap.dedent(test_body), ".cpp")
            context.Result(ret)
            return ret

        conf = Configure(myenv, help=False, custom_tests = {
            'CheckNullConversion' : CheckNullConversion,
        })
        if conf.CheckNullConversion() == False:
            env.Append( CCFLAGS="-Wno-null-conversion" )
        conf.Finish()

    # This needs to happen before we check for libc++, since it affects whether libc++ is available.
    if darwin and has_option('osx-version-min'):
        min_version = get_option('osx-version-min')
        min_version_flag = '-mmacosx-version-min=%s' % (min_version)
        if not AddToCCFLAGSIfSupported(myenv, min_version_flag):
            myenv.ConfError("Can't set minimum OS X version with this compiler")
        myenv.AppendUnique(LINKFLAGS=[min_version_flag])

    usingLibStdCxx = False
    if has_option('libc++'):
        if not using_clang():
            myenv.ConfError('libc++ is currently only supported for clang')
        if darwin and has_option('osx-version-min') and versiontuple(min_version) < versiontuple('10.7'):
            print("Warning: You passed option 'libc++'. You probably want to also pass 'osx-version-min=10.7' or higher for libc++ support.")
        if AddToCXXFLAGSIfSupported(myenv, '-stdlib=libc++'):
            myenv.Append(LINKFLAGS=['-stdlib=libc++'])
        else:
            myenv.ConfError('libc++ requested, but compiler does not support -stdlib=libc++' )
    else:
        def CheckLibStdCxx(context):
            test_body = """
            #include <vector>
            #if !defined(__GLIBCXX__)
            #error
            #endif
            """

            context.Message('Checking if we are using libstdc++... ')
            ret = context.TryCompile(textwrap.dedent(test_body), ".cpp")
            context.Result(ret)
            return ret

        conf = Configure(myenv, help=False, custom_tests = {
            'CheckLibStdCxx' : CheckLibStdCxx,
        })
        usingLibStdCxx = conf.CheckLibStdCxx()
        conf.Finish()

    # Check to see if we are trying to use an elderly libstdc++, which we arbitrarily define as
    # 4.6.0. This is primarly to help people using clang in C++11 mode on OS X but forgetting
    # to use --libc++. We also use it to decide if we trust the libstdc++ debug mode. We would,
    # ideally, check the __GLIBCXX__ version, but for various reasons this is not
    # workable. Instead, we switch on the fact that _GLIBCXX_BEGIN_NAMESPACE_VERSION wasn't
    # introduced until libstdc++ 4.6.0.

    haveGoodLibStdCxx = False
    if usingLibStdCxx:

        def CheckModernLibStdCxx(context):

            test_body = """
            #include <vector>
            #if !defined(_GLIBCXX_BEGIN_NAMESPACE_VERSION)
            #error libstdcxx older than 4.6.0
            #endif
            """

            context.Message('Checking for libstdc++ 4.6.0 or better... ')
            ret = context.TryCompile(textwrap.dedent(test_body), ".cpp")
            context.Result(ret)
            return ret

        conf = Configure(myenv, help=False, custom_tests = {
            'CheckModernLibStdCxx' : CheckModernLibStdCxx,
        })
        haveGoodLibStdCxx = conf.CheckModernLibStdCxx()
        conf.Finish()

    # Sort out whether we can and should use C++11:
    cxx11_mode = get_option("c++11")

    if using_msvc():
        if cxx11_mode == "off":
            print( 'WARNING: Cannot disable C++11 features when using MSVC' )
    else:

        # If we are using libstdc++, only allow C++11 mode with our line-in-the-sand good
        # libstdc++. As always, if in auto mode fall back to disabling if we don't have a good
        # libstdc++, otherwise fail the build because we can't honor the explicit request.
        if cxx11_mode != "off" and usingLibStdCxx:
            if not haveGoodLibStdCxx:
                if cxx11_mode == "auto":
                    cxx11_mode = "off"
                else:
                    cxx11_error = 'Detected libstdc++ is too old to support C++11 mode'
                    if darwin:
                        cxx11_error += \
                            '\nTry building with --libc++ and --osx-version-min=10.7 or higher'
                    myenv.ConfError(cxx11_error)

        # We are going to be adding flags to the environment, but we don't want to persist
        # those changes unless we pass all the below checks. Make a copy of the environment
        # that we will modify, we will only "commit" the changes to the env if we pass all the
        # checks.
        cxx11Env = myenv.Clone()

        # For our other compilers (gcc and clang) we need to pass -std=c++0x or -std=c++11,
        # but we prefer the latter. Try that first, and fall back to c++0x if we don't
        # detect that --std=c++11 works. If we can't find a flag and C++11 was explicitly
        # requested, error out, otherwise turn off C++11 support in auto mode.
        if cxx11_mode != "off":
            if not AddToCXXFLAGSIfSupported(cxx11Env, '-std=c++11'):
                if not AddToCXXFLAGSIfSupported(cxx11Env, '-std=c++0x'):
                    if cxx11_mode == "auto":
                        cxx11_mode = "off"
                    else:
                        cxx11Env.ConfError(
                            'C++11 mode requested, but cannot find a flag to enable it')

        # We appear to have C++11, or at least a flag to enable it, which is now set in the
        # environment. If we are in auto mode, check if the compiler claims that it strictly
        # supports C++11, and disable C++11 if not. If the user has explicitly requested C++11,
        # we don't care about what the compiler claims to support, trust the user.
        if cxx11_mode == "auto":
            def CheckCxx11Official(context):
                test_body = """
                #if __cplusplus < 201103L
                #error
                #endif
                const int not_an_empty_file = 0;
                """

                context.Message('Checking if __cplusplus >= 201103L to auto-enable C++11... ')
                ret = context.TryCompile(textwrap.dedent(test_body), ".cpp")
                context.Result(ret)
                return ret

            conf = Configure(cxx11Env, help=False, custom_tests = {
                'CheckCxx11Official' : CheckCxx11Official,
            })

            if cxx11_mode == "auto" and not conf.CheckCxx11Official():
                cxx11_mode = "off"

            conf.Finish()

        # We require c99 mode for C files when C++11 is enabled, so perform the same dance
        # as above: if C++11 mode is not off, try the flag, if we are in auto mode and we fail
        # then turn off C++11, otherwise C++11 was explicitly requested and we should error out.
        if cxx11_mode != "off":
            if not AddToCFLAGSIfSupported(cxx11Env, '-std=c99'):
                if cxx11_mode == "auto":
                    cxx11_mode = "off"
                else:
                    cxx11Env.ConfError(
                        "C++11 mode selected for C++ files, but can't enable C99 for C files")

        # If we got here and cxx11_mode hasn't become false, then its true, so swap in the
        # modified environment.
        if cxx11_mode != "off":
            cxx11_mode = "on"
            myenv = cxx11Env

    # Check if we are on a POSIX system by testing if _POSIX_VERSION is defined.
    def CheckPosixSystem(context):

        test_body = """
        // POSIX requires the existence of unistd.h, so if we can't include unistd.h, we
        // are definitely not a POSIX system.
        #include <unistd.h>
        #if !defined(_POSIX_VERSION)
        #error not a POSIX system
        #endif
        """

        context.Message('Checking if we are on a POSIX system... ')
        ret = context.TryCompile(textwrap.dedent(test_body), ".c")
        context.Result(ret)
        return ret

    conf = Configure(myenv, help=False, custom_tests = {
        'CheckPosixSystem' : CheckPosixSystem,
    })
    posix_system = conf.CheckPosixSystem()
    conf.Finish()

    # Check if we are on a system that support the POSIX clock_gettime function
    #  and the "monotonic" clock.
    posix_monotonic_clock = False
    if posix_system:
        def CheckPosixMonotonicClock(context):

            test_body = """
            #include <unistd.h>
            #if !(defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
            #error POSIX clock_gettime not supported
            #elif !(defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0)
            #error POSIX monotonic clock not supported
            #endif
            """

            context.Message('Checking if the POSIX monotonic clock is supported... ')
            ret = context.TryCompile(textwrap.dedent(test_body), ".c")
            context.Result(ret)
            return ret

        conf = Configure(myenv, help=False, custom_tests = {
            'CheckPosixMonotonicClock' : CheckPosixMonotonicClock,
        })
        posix_monotonic_clock = conf.CheckPosixMonotonicClock()
        conf.Finish()

    if has_option('sanitize'):

        if not (using_clang() or using_gcc()):
            myenv.FatalError('sanitize is only supported with clang or gcc')

        sanitizer_list = get_option('sanitize').split(',')

        using_lsan = 'leak' in sanitizer_list
        using_asan = 'address' in sanitizer_list or using_lsan

        # If the user asked for leak sanitizer turn on the detect_leaks
        # ASAN_OPTION. If they asked for address sanitizer as well, drop
        # 'leak', because -fsanitize=leak means no address.
        #
        # --sanitize=leak:           -fsanitize=leak, detect_leaks=1
        # --sanitize=address,leak:   -fsanitize=address, detect_leaks=1
        # --sanitize=address:        -fsanitize=address
        #
        if using_lsan:
            if using_asan:
                myenv['ENV']['ASAN_OPTIONS'] = "detect_leaks=1"
            myenv['ENV']['LSAN_OPTIONS'] = "suppressions=%s" % myenv.File("#etc/lsan.suppressions").abspath
            if 'address' in sanitizer_list:
                sanitizer_list.remove('leak')

        sanitizer_option = '-fsanitize=' + ','.join(sanitizer_list)

        if AddToCCFLAGSIfSupported(myenv, sanitizer_option):
            myenv.Append(LINKFLAGS=[sanitizer_option])
            myenv.Append(CCFLAGS=['-fno-omit-frame-pointer'])
        else:
            myenv.ConfError('Failed to enable sanitizers with flag: {0}', sanitizer_option )

        blackfiles_map = {
            "address" : myenv.File("#etc/asan.blacklist"),
            "leak" : myenv.File("#etc/asan.blacklist"),
            "thread" : myenv.File("#etc/tsan.blacklist"),
            "undefined" : myenv.File("#etc/ubsan.blacklist"),
        }

        blackfiles = set([v for (k, v) in blackfiles_map.iteritems() if k in sanitizer_list])
        blacklist_options=["-fsanitize-blacklist=%s" % blackfile for blackfile in blackfiles]

        for blacklist_option in blacklist_options:
            if AddToCCFLAGSIfSupported(myenv, blacklist_option):
                myenv.Append(LINKFLAGS=[blacklist_option])

        llvm_symbolizer = get_option('llvm-symbolizer')
        if os.path.isabs(llvm_symbolizer):
            if not myenv.File(llvm_symbolizer).exists():
                print("WARNING: Specified symbolizer '%s' not found" % llvm_symbolizer)
                llvm_symbolizer = None
        else:
            llvm_symbolizer = myenv.WhereIs(llvm_symbolizer)

        if llvm_symbolizer:
            myenv['ENV']['ASAN_SYMBOLIZER_PATH'] = llvm_symbolizer
            myenv['ENV']['LSAN_SYMBOLIZER_PATH'] = llvm_symbolizer
        elif using_lsan:
            myenv.ConfError("Using the leak sanitizer requires a valid symbolizer")

    # When using msvc, check for VS 2013 Update 2+ so we can use new compiler flags
    if using_msvc():
        haveVS2013Update2OrLater = False
        def CheckVS2013Update2(context):
            test_body = """
            #if _MSC_VER < 1800 || (_MSC_VER == 1800 && _MSC_FULL_VER < 180030501)
            #error Old Version
            #endif
            int main(int argc, char* argv[]) {
            return 0;
            }
            """
            context.Message('Checking for VS 2013 Update 2 or Later... ')
            ret = context.TryCompile(textwrap.dedent(test_body), ".cpp")
            context.Result(ret)
            return ret
        conf = Configure(myenv, help=False, custom_tests = {
            'CheckVS2013Update2' : CheckVS2013Update2,
        })
        haveVS2013Update2OrLater = conf.CheckVS2013Update2()
        conf.Finish()

        if haveVS2013Update2OrLater and optBuild:
            # http://blogs.msdn.com/b/vcblog/archive/2013/09/11/introducing-gw-compiler-switch.aspx
            #
            myenv.Append( CCFLAGS=["/Gw", "/Gy"] )
            myenv.Append( LINKFLAGS=["/OPT:REF"])

            # http://blogs.msdn.com/b/vcblog/archive/2014/03/25/linker-enhancements-in-visual-studio-2013-update-2-ctp2.aspx
            #
            myenv.Append( CCFLAGS=["/Zc:inline"])

    # Apply any link time optimization settings as selected by the 'lto' option.
    if has_option('lto'):
        if using_msvc():
            # Note that this is actually more aggressive than LTO, it is whole program
            # optimization due to /GL. However, this is historically what we have done for
            # windows, so we are keeping it.
            #
            # /GL implies /LTCG, so no need to say it in CCFLAGS, but we do need /LTCG on the
            # link flags.
            myenv.Append(CCFLAGS=['/GL'])
            myenv.Append(LINKFLAGS=['/LTCG'])
            myenv.Append(ARFLAGS=['/LTCG'])
        elif using_gcc() or using_clang():
            # For GCC and clang, the flag is -flto, and we need to pass it both on the compile
            # and link lines.
            if AddToCCFLAGSIfSupported(myenv, '-flto'):
                myenv.Append(LINKFLAGS=['-flto'])

                def LinkHelloWorld(context, adornment = None):
                    test_body = """
                    #include <iostream>
                    int main() {
                        std::cout << "Hello, World!" << std::endl;
                        return 0;
                    }
                    """
                    message = "Trying to link with LTO"
                    if adornment:
                        message = message + " " + adornment
                    message = message + "..."
                    context.Message(message)
                    ret = context.TryLink(textwrap.dedent(test_body), ".cpp")
                    context.Result(ret)
                    return ret

                conf = Configure(myenv, help=False, custom_tests = {
                    'LinkHelloWorld' : LinkHelloWorld,
                })

                # Some systems (clang, on a system with the BFD linker by default) may need to
                # explicitly request the gold linker for LTO to work. If we can't LTO link a
                # simple program, see if -fuse=ld=gold helps.
                if not conf.LinkHelloWorld():
                    conf.env.Append(LINKFLAGS=["-fuse-ld=gold"])
                    if not conf.LinkHelloWorld("(with -fuse-ld=gold)"):
                        myenv.ConfError("Error: Couldn't link with LTO")

                myenv = conf.Finish()

            else:
                myenv.ConfError("Link time optimization requested, " +
                    "but selected compiler does not honor -flto" )
        else:
            myenv.ConfError("Don't know how to enable --lto on current toolchain")

    # When using msvc, check for support for __declspec(thread), unless we have been asked
    # explicitly not to use it. For other compilers, see if __thread works.
    if using_msvc():
        haveDeclSpecThread = False
        if not has_option("disable-declspec-thread"):
            def CheckDeclspecThread(context):
                test_body = """
                __declspec( thread ) int tsp_int;
                int main(int argc, char* argv[]) {
                    tsp_int = argc;
                    return 0;
                }
                """
                context.Message('Checking for __declspec(thread)... ')
                ret = context.TryLink(textwrap.dedent(test_body), ".cpp")
                context.Result(ret)
                return ret
            conf = Configure(myenv, help=False, custom_tests = {
                'CheckDeclspecThread' : CheckDeclspecThread,
            })
            haveDeclSpecThread = conf.CheckDeclspecThread()
            conf.Finish()
        if haveDeclSpecThread:
            myenv.Append(CPPDEFINES=['MONGO_HAVE___DECLSPEC_THREAD'])
    else:
        def CheckUUThread(context):
            test_body = """
            __thread int tsp_int;
            int main(int argc, char* argv[]) {
                tsp_int = argc;
                return 0;
            }
            """
            context.Message('Checking for __thread... ')
            ret = context.TryLink(textwrap.dedent(test_body), ".cpp")
            context.Result(ret)
            return ret
        conf = Configure(myenv, help=False, custom_tests = {
            'CheckUUThread' : CheckUUThread,
        })
        haveUUThread = conf.CheckUUThread()
        conf.Finish()
        if haveUUThread:
            myenv.Append(CPPDEFINES=['MONGO_HAVE___THREAD'])

    def CheckCXX11Atomics(context):
        test_body = """
        #include <atomic>
        int main(int argc, char **argv) {
            std::atomic<long long> a(0);
            return a.fetch_add(1);
        }
        """
        context.Message('Checking for C++11 <atomic> support... ')
        ret = context.TryLink(textwrap.dedent(test_body), '.cpp')
        context.Result(ret)
        return ret;

    def CheckGCCAtomicBuiltins(context):
        test_body = """
        int main(int argc, char **argv) {
            long long a = 0;
            long long b = 0;
            long long c = 0;

            __atomic_compare_exchange(&a, &b, &c, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
            return 0;
        }
        """
        context.Message('Checking for gcc __atomic builtins... ')
        ret = context.TryLink(textwrap.dedent(test_body), '.cpp')
        context.Result(ret)
        return ret

    def CheckGCCSyncBuiltins(context):
        test_body = """
        int main(int argc, char **argv) {
            long long a = 0;
            return __sync_fetch_and_add(&a, 1);
        }

        //
        // Figure out if we are using gcc older than 4.2 to target 32-bit x86. If so, error out
        // even if we were able to compile the __sync statement, due to
        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40693
        //
        #if defined(__i386__)
        #if !defined(__clang__)
        #if defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 2)
        #error "Refusing to use __sync in 32-bit mode with gcc older than 4.2"
        #endif
        #endif
        #endif
        """

        context.Message('Checking for useable __sync builtins... ')
        ret = context.TryLink(textwrap.dedent(test_body), '.cpp')
        context.Result(ret)
        return ret

    # not all C++11-enabled gcc versions have type properties
    def CheckCXX11IsTriviallyCopyable(context):
        test_body = """
        #include <type_traits>
        int main(int argc, char **argv) {
            class Trivial {
                int trivial1;
                double trivial2;
                struct {
                    float trivial3;
                    short trivial4;
                } trivial_member;
            };

            class NotTrivial {
                int x, y;
                NotTrivial(const NotTrivial& o) : x(o.y), y(o.x) {}
            };

            static_assert(std::is_trivially_copyable<Trivial>::value,
                          "I should be trivially copyable");
            static_assert(!std::is_trivially_copyable<NotTrivial>::value,
                          "I should not be trivially copyable");
            return 0;
        }
        """
        context.Message('Checking for C++11 is_trivially_copyable support... ')
        ret = context.TryCompile(textwrap.dedent(test_body), '.cpp')
        context.Result(ret)
        return ret

    conf = Configure(myenv, help=False, custom_tests = {
        'CheckCXX11Atomics': CheckCXX11Atomics,
        'CheckGCCAtomicBuiltins': CheckGCCAtomicBuiltins,
        'CheckGCCSyncBuiltins': CheckGCCSyncBuiltins,
        'CheckCXX11IsTriviallyCopyable': CheckCXX11IsTriviallyCopyable,
    })

    # Figure out what atomics mode to use by way of the tests defined above.
    #
    # Non_windows: <atomic> > __atomic > __sync
    # Windows: <atomic> > Interlocked functions / intrinsics.
    #
    # If we are in C++11 mode, try to use <atomic>. This is unusual for us, as typically we
    # only use __cplusplus >= 201103L to decide if we want to enable a feature. We make a
    # special case for the atomics and use them on platforms that offer them even if they don't
    # advertise full conformance. For MSVC systems, if we don't have <atomic> then no more
    # checks are required. Otherwise, we are on a GCC/clang system, where we may have __atomic
    # or __sync, so try those in that order next.
    #
    # If we don't end up defining a MONGO_HAVE for the atomics, we will end up falling back to
    # the Microsoft Interlocked functions/intrinsics when using MSVC, or the gcc_intel
    # implementation of hand-rolled assembly if using gcc/clang.

    if (using_msvc() or (cxx11_mode == "on")) and conf.CheckCXX11Atomics():
        conf.env['MONGO_HAVE_CXX11_ATOMICS'] = True
    elif using_gcc() or using_clang():
        # Prefer the __atomic builtins. If we don't have those, try for __sync. Otherwise
        # atomic_intrinsics.h will try to fall back to the hand-rolled assembly implementations
        # in atomic_intrinsics_gcc_intel for x86 platforms.
        if conf.CheckGCCAtomicBuiltins():
            conf.env["MONGO_HAVE_GCC_ATOMIC_BUILTINS"] = True
        else:
            if conf.CheckGCCSyncBuiltins():
                conf.env["MONGO_HAVE_GCC_SYNC_BUILTINS"] = True

    if (cxx11_mode == "on") and conf.CheckCXX11IsTriviallyCopyable():
        conf.env['MONGO_HAVE_STD_IS_TRIVIALLY_COPYABLE'] = True

    myenv = conf.Finish()

    if using_msvc():
        # TODO: This is really only needed for MSVC 12, but we have no current way to know
        # which MSVC version we have. Presuming that this is harmless on other MSVC
        # implementations. Without this, gtest doesn't build. We need to apply universally, not
        # just while builing gtest.
        myenv.Append(CPPDEFINES=[('_VARIADIC_MAX', 10)])

    conf = Configure(myenv)

    conf.env["MONGO_SSL"] = bool(has_option("ssl"))
    if conf.env["MONGO_SSL"]:
        sslLibName = "ssl"
        cryptoLibName = "crypto"
        if windows:
            sslLibName = "ssleay32"
            cryptoLibName = "libeay32"

        if not conf.CheckLibWithHeader(
                sslLibName,
                ["openssl/ssl.h"],
                "C",
                "SSL_version(NULL);",
                autoadd=True):
            conf.env.ConfError("Couldn't find OpenSSL ssl.h header and library")

        if not conf.CheckLibWithHeader(
                cryptoLibName,
                ["openssl/crypto.h"],
                "C",
                "SSLeay_version(0);",
                autoadd=True):
            conf.env.ConfError("Couldn't find OpenSSL crypto.h header and library")

        def CheckLinkSSL(context):
            test_body = """
            #include <openssl/err.h>
            #include <openssl/ssl.h>
            #include <stdlib.h>

            int main() {
                SSL_library_init();
                SSL_load_error_strings();
                ERR_load_crypto_strings();

                OpenSSL_add_all_algorithms();
                ERR_free_strings();

                return EXIT_SUCCESS;
            }
            """
            context.Message("Checking that linking to OpenSSL works...")
            ret = context.TryLink(textwrap.dedent(test_body), ".c")
            context.Result(ret)
            return ret

        conf.AddTest("CheckLinkSSL", CheckLinkSSL)

        if not conf.CheckLinkSSL():
            conf.env.ConfError("SSL is enabled, but is unavailable")

        if conf.CheckDeclaration(
            "FIPS_mode_set",
            includes="""
                #include <openssl/crypto.h>
                #include <openssl/evp.h>
            """):

            conf.env.Append(CPPDEFINES=["MONGO_HAVE_FIPS_MODE_SET"])

    if not conf.CheckCXXHeader( "boost/version.hpp" ):
        conf.env.ConfError("Could not find boost headers in include search path")

    if (not windows) and boostSuffixList:
        # We don't do this for windows because we rely on autolib.
        for b in boostLibs:
            boostCandidates = ["boost_" + b + suffix for suffix in boostSuffixList]
            if not conf.CheckLib(boostCandidates, language="C++"):
                conf.env.ConfError("can't find boost")

    # We need xtime internally no matter what the local boost thread version may be since we
    # cannot require the existence of chrono. It is important that no uses of xtime become part
    # of the public interface of the library so that we do not impose this burden on our
    # consumers.
    conf.env.Append(CPPDEFINES=[("BOOST_THREAD_USES_DATETIME")])

    if conf.CheckHeader('unistd.h'):
        conf.env['MONGO_HAVE_HEADER_UNISTD_H'] = True

    if posix_system:
        conf.env.Append(CPPDEFINES=['MONGO_HAVE_HEADER_UNISTD_H'])
        conf.CheckLib('rt')

    if posix_monotonic_clock:
        conf.env.Append(CPPDEFINES=['MONGO_HAVE_POSIX_MONOTONIC_CLOCK'])

    if solaris:
        conf.CheckLib( "nsl" )

    conf.env['MONGO_SASL'] = bool(has_option("use-sasl-client"))

    if conf.env['MONGO_SASL'] and not conf.env['MONGO_SSL']:
        myenv.FatalError("SASL support requires --ssl")

    if conf.env['MONGO_SASL'] and not conf.CheckLibWithHeader(
            "sasl2", 
            ["stddef.h","sasl/sasl.h"], 
            "C", 
            "sasl_version_info(0, 0, 0, 0, 0, 0);", 
            autoadd=True ):
        myenv.ConfError("Couldn't find SASL header/libraries")

    # requires ports devel/libexecinfo to be installed
    if freebsd or openbsd:
        if not conf.CheckLib("execinfo"):
            myenv.ConfError("Cannot find libexecinfo, please install devel/libexecinfo")

    # check for presence of timegm(3) and polyfill if needed
    conf.env['MONGO_HAVE_TIMEGM'] = conf.CheckDeclaration(
        'timegm', includes="#include <time.h>", language='C')
    if conf.env['MONGO_HAVE_TIMEGM']:
        conf.env.Append(CPPDEFINES=['MONGO_HAVE_TIMEGM'])

    # check for presence of strnlen(3) and polyfill if needed
    if conf.CheckDeclaration('strnlen', includes="#include <string.h>", language='C'):
        conf.env['MONGO_HAVE_STRNLEN'] = True

    return conf.Finish()

env = doConfigure( env )

env['PDB'] = '${TARGET.base}.pdb'

#  ---- Docs ----
def build_docs(env, target, source):
    buildscripts.docs.main()

env.Alias("docs", [], [build_docs])
env.AlwaysBuild("docs")

# --- lint ----

def doLint( env , target , source ):
    import buildscripts.clang_format
    if not buildscripts.clang_format.lint(None, []):
        raise Exception("clang-format lint errors")

    if not buildscripts.lint.run_lint( [ "src/mongo/" ] ):
        raise Exception( "lint errors" )

env.Alias( "lint" , [] , [ doLint ] )
env.AlwaysBuild( "lint" )

# --- an uninstall target ---
if len(COMMAND_LINE_TARGETS) > 0 and 'uninstall' in COMMAND_LINE_TARGETS:
    SetOption("clean", 1)
    # By inspection, changing COMMAND_LINE_TARGETS here doesn't do
    # what we want, but changing BUILD_TARGETS does.
    BUILD_TARGETS.remove("uninstall")
    BUILD_TARGETS.append("install")

# The following symbols are exported for use in subordinate SConscript files.
# Ideally, the SConscript files would be purely declarative.  They would only
# import build environment objects, and would contain few or no conditional
# statements or branches.
#
# Currently, however, the SConscript files do need some predicates for
# conditional decision making that hasn't been moved up to this SConstruct file,
# and they are exported here, as well.
Export("env")
Export("get_option")
Export("has_option")
Export("darwin windows solaris linux freebsd nix")
Export("debugBuild optBuild")
Export("use_clang")

env.SConscript('src/SConscript', variant_dir='$VARIANT_DIR', duplicate=False)

# --- Coverage ---
if has_option("gcov"):
    env['GCOV_BASE_DIR'] = env.Dir(".").abspath
    env['GCOV_BUILD_DIR'] = env.Dir("$VARIANT_DIR").abspath

    # Zero out all the counters -- depends on tests being built
    env.Alias(
        'zero_counters',
        ['unittests', 'clientTests', 'integration_tests'],
        ['lcov -z -b $GCOV_BASE_DIR -d $GCOV_BUILD_DIR']
    )
    env.AlwaysBuild('zero_counters')

    # Generates test coverage information -- depends on tests being run
    env.Command(
        target='$VARIANT_DIR/coverage.info',
        source=['zero_counters', 'test', 'smokeClient', 'integration'],
        action='lcov --no-external -c -b $GCOV_BASE_DIR -d $GCOV_BUILD_DIR -o $TARGET'
    )
    env.AlwaysBuild('coverage.info')

    # Strip third_party and build related coverage info
    stripCmd = env.Command(
        target=None,
        source='$VARIANT_DIR/coverage.info',
        action=[
            'lcov -r $SOURCE src/third_party/\* -o $SOURCE',
            'lcov -r $SOURCE build/\* -o $SOURCE',
            'lcov -r $SOURCE \*_test.cpp -o $SOURCE',
            'lcov -r $SOURCE src/mongo/client/examples/\* -o $SOURCE',
            'lcov -r $SOURCE src/mongo/dbtests/\* -o $SOURCE',
            'lcov -r $SOURCE src/mongo/unittest/\* -o $SOURCE',
            'lcov -r $SOURCE src/mongo/bson/bsondemo/\* -o $SOURCE',
        ],
    )
    env.AlwaysBuild(stripCmd)
    env.Alias('strip_coverage', stripCmd)

    # Generates the HTML output in "coverage" directory
    coverageCmd = env.Command(
        env.Dir('$BUILD_DIR/coverage'),
        'strip_coverage',
        [
            'rm -rf $BUILD_DIR/coverage',
            'genhtml --frames --legend -t "MongoDB C++ Driver Coverage" -o $TARGET $VARIANT_DIR/coverage.info'
        ]
    )
    env.AlwaysBuild(coverageCmd)
    env.Alias('coverage', coverageCmd)

env.Alias('all', ['driver', 'build-unit', 'build-integration', 'build-examples'])
env.Alias('test', ['unit', 'integration', 'examples'])

Default('driver')