SConstruct

   1 # -*- mode:python -*-
   2
   3 # Copyright (c) 2013, 2015-2020 ARM Limited
   4 # All rights reserved.
   5 #
   6 # The license below extends only to copyright in the software and shall
   7 # not be construed as granting a license to any other intellectual
   8 # property including but not limited to intellectual property relating
   9 # to a hardware implementation of the functionality of the software
  10 # licensed hereunder.  You may use the software subject to the license
  11 # terms below provided that you ensure that this notice is replicated
  12 # unmodified and in its entirety in all distributions of the software,
  13 # modified or unmodified, in source code or in binary form.
  14 #
  15 # Copyright (c) 2011 Advanced Micro Devices, Inc.
  16 # Copyright (c) 2009 The Hewlett-Packard Development Company
  17 # Copyright (c) 2004-2005 The Regents of The University of Michigan
  18 # All rights reserved.
  19 #
  20 # Redistribution and use in source and binary forms, with or without
  21 # modification, are permitted provided that the following conditions are
  22 # met: redistributions of source code must retain the above copyright
  23 # notice, this list of conditions and the following disclaimer;
  24 # redistributions in binary form must reproduce the above copyright
  25 # notice, this list of conditions and the following disclaimer in the
  26 # documentation and/or other materials provided with the distribution;
  27 # neither the name of the copyright holders nor the names of its
  28 # contributors may be used to endorse or promote products derived from
  29 # this software without specific prior written permission.
  30 #
  31 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  32 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  33 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  34 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  35 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  36 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  37 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  38 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  39 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  40 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  41 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  42
  43 ###################################################
  44 #
  45 # SCons top-level build description (SConstruct) file.
  46 #
  47 # While in this directory ('gem5'), just type 'scons' to build the default
  48 # configuration (see below), or type 'scons build/<CONFIG>/<binary>'
  49 # to build some other configuration (e.g., 'build/X86/gem5.opt' for
  50 # the optimized full-system version).
  51 #
  52 # You can build gem5 in a different directory as long as there is a
  53 # 'build/<CONFIG>' somewhere along the target path.  The build system
  54 # expects that all configs under the same build directory are being
  55 # built for the same host system.
  56 #
  57 # Examples:
  58 #
  59 #   The following two commands are equivalent.  The '-u' option tells
  60 #   scons to search up the directory tree for this SConstruct file.
  61 #   % cd <path-to-src>/gem5 ; scons build/X86/gem5.debug
  62 #   % cd <path-to-src>/gem5/build/X86; scons -u gem5.debug
  63 #
  64 #   The following two commands are equivalent and demonstrate building
  65 #   in a directory outside of the source tree.  The '-C' option tells
  66 #   scons to chdir to the specified directory to find this SConstruct
  67 #   file.
  68 #   % cd <path-to-src>/gem5 ; scons /local/foo/build/X86/gem5.debug
  69 #   % cd /local/foo/build/X86; scons -C <path-to-src>/gem5 gem5.debug
  70 #
  71 # You can use 'scons -H' to print scons options.  If you're in this
  72 # 'gem5' directory (or use -u or -C to tell scons where to find this
  73 # file), you can use 'scons -h' to print all the gem5-specific build
  74 # options as well.
  75 #
  76 ###################################################
  77
  78 # Global Python includes
  79 import atexit
  80 import itertools
  81 import os
  82 import re
  83 import shutil
  84 import subprocess
  85 import sys
  86
  87 from os import mkdir, environ
  88 from os.path import abspath, basename, dirname, expanduser, normpath
  89 from os.path import exists,  isdir, isfile
  90 from os.path import join as joinpath, split as splitpath
  91 from re import match
  92
  93 # SCons includes
  94 import SCons
  95 import SCons.Node
  96 import SCons.Node.FS
  97
  98 from m5.util import compareVersions, readCommand, readCommandWithReturn
  99
 100 AddOption('--colors', dest='use_colors', action='store_true',
 101           help="Add color to abbreviated scons output")
 102 AddOption('--no-colors', dest='use_colors', action='store_false',
 103           help="Don't add color to abbreviated scons output")
 104 AddOption('--with-cxx-config', action='store_true',
 105           help="Build with support for C++-based configuration")
 106 AddOption('--default',
 107           help='Override which build_opts file to use for defaults')
 108 AddOption('--ignore-style', action='store_true',
 109           help='Disable style checking hooks')
 110 AddOption('--gold-linker', action='store_true', help='Use the gold linker')
 111 AddOption('--no-compress-debug', action='store_true',
 112           help="Don't compress debug info in build files")
 113 AddOption('--no-lto', action='store_true',
 114           help='Disable Link-Time Optimization for fast')
 115 AddOption('--verbose', action='store_true',
 116           help='Print full tool command lines')
 117 AddOption('--without-python', action='store_true',
 118           help='Build without Python configuration support')
 119 AddOption('--without-tcmalloc', action='store_true',
 120           help='Disable linking against tcmalloc')
 121 AddOption('--with-ubsan', action='store_true',
 122           help='Build with Undefined Behavior Sanitizer if available')
 123 AddOption('--with-asan', action='store_true',
 124           help='Build with Address Sanitizer if available')
 125 AddOption('--with-systemc-tests', action='store_true',
 126           help='Build systemc tests')
 127
 128 from gem5_scons import Transform, error, warning, summarize_warnings
 129 import gem5_scons
 130
 131 ########################################################################
 132 #
 133 # Set up the main build environment.
 134 #
 135 ########################################################################
 136
 137 main = Environment(tools=['default', 'git'])
 138
 139 from gem5_scons.util import get_termcap
 140 termcap = get_termcap()
 141
 142 main_dict_keys = main.Dictionary().keys()
 143
 144 # Check that we have a C/C++ compiler
 145 if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
 146     error("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
 147
 148 ###################################################
 149 #
 150 # Figure out which configurations to set up based on the path(s) of
 151 # the target(s).
 152 #
 153 ###################################################
 154
 155 # Find default configuration & binary.
 156 Default(environ.get('M5_DEFAULT_BINARY', 'build/ARM/gem5.debug'))
 157
 158 # helper function: find last occurrence of element in list
 159 def rfind(l, elt, offs = -1):
 160     for i in range(len(l)+offs, 0, -1):
 161         if l[i] == elt:
 162             return i
 163     raise ValueError("element not found")
 164
 165 # Take a list of paths (or SCons Nodes) and return a list with all
 166 # paths made absolute and ~-expanded.  Paths will be interpreted
 167 # relative to the launch directory unless a different root is provided
 168 def makePathListAbsolute(path_list, root=GetLaunchDir()):
 169     return [abspath(joinpath(root, expanduser(str(p))))
 170             for p in path_list]
 171
 172 # Each target must have 'build' in the interior of the path; the
 173 # directory below this will determine the build parameters.  For
 174 # example, for target 'foo/bar/build/X86/arch/x86/blah.do' we
 175 # recognize that X86 specifies the configuration because it
 176 # follow 'build' in the build path.
 177
 178 # The funky assignment to "[:]" is needed to replace the list contents
 179 # in place rather than reassign the symbol to a new list, which
 180 # doesn't work (obviously!).
 181 BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
 182
 183 # Generate a list of the unique build roots and configs that the
 184 # collected targets reference.
 185 variant_paths = []
 186 build_root = None
 187 for t in BUILD_TARGETS:
 188     path_dirs = t.split('/')
 189     try:
 190         build_top = rfind(path_dirs, 'build', -2)
 191     except:
 192         error("No non-leaf 'build' dir found on target path.", t)
 193     this_build_root = joinpath('/',*path_dirs[:build_top+1])
 194     if not build_root:
 195         build_root = this_build_root
 196     else:
 197         if this_build_root != build_root:
 198             error("build targets not under same build root\n"
 199                   "  %s\n  %s" % (build_root, this_build_root))
 200     variant_path = joinpath('/',*path_dirs[:build_top+2])
 201     if variant_path not in variant_paths:
 202         variant_paths.append(variant_path)
 203
 204 # Make sure build_root exists (might not if this is the first build there)
 205 if not isdir(build_root):
 206     mkdir(build_root)
 207 main['BUILDROOT'] = build_root
 208
 209 Export('main')
 210
 211 main.SConsignFile(joinpath(build_root, "sconsign"))
 212
 213 # Default duplicate option is to use hard links, but this messes up
 214 # when you use emacs to edit a file in the target dir, as emacs moves
 215 # file to file~ then copies to file, breaking the link.  Symbolic
 216 # (soft) links work better.
 217 main.SetOption('duplicate', 'soft-copy')
 218
 219 #
 220 # Set up global sticky variables... these are common to an entire build
 221 # tree (not specific to a particular build like X86)
 222 #
 223
 224 global_vars_file = joinpath(build_root, 'variables.global')
 225
 226 global_vars = Variables(global_vars_file, args=ARGUMENTS)
 227
 228 global_vars.AddVariables(
 229     ('CC', 'C compiler', environ.get('CC', main['CC'])),
 230     ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
 231     ('CCFLAGS_EXTRA', 'Extra C and C++ compiler flags', ''),
 232     ('LDFLAGS_EXTRA', 'Extra linker flags', ''),
 233     ('MARSHAL_CCFLAGS_EXTRA', 'Extra C and C++ marshal compiler flags', ''),
 234     ('MARSHAL_LDFLAGS_EXTRA', 'Extra marshal linker flags', ''),
 235     ('PYTHON_CONFIG', 'Python config binary to use',
 236      [ 'python3-config', 'python-config']
 237     ),
 238     ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
 239     ('BATCH', 'Use batch pool for build and tests', False),
 240     ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
 241     ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
 242     ('EXTRAS', 'Add extra directories to the compilation', '')
 243     )
 244
 245 # Update main environment with values from ARGUMENTS & global_vars_file
 246 global_vars.Update(main)
 247 Help('''
 248 Global build variables:
 249 {help}
 250 '''.format(help=global_vars.GenerateHelpText(main)), append=True)
 251
 252 # Save sticky variable settings back to current variables file
 253 global_vars.Save(global_vars_file, main)
 254
 255 # Parse EXTRAS variable to build list of all directories where we're
 256 # look for sources etc.  This list is exported as extras_dir_list.
 257 base_dir = Dir('#src').abspath
 258 if main['EXTRAS']:
 259     extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
 260 else:
 261     extras_dir_list = []
 262
 263 Export('base_dir')
 264 Export('extras_dir_list')
 265
 266 # the ext directory should be on the #includes path
 267 main.Append(CPPPATH=[Dir('ext')])
 268
 269 # Add shared top-level headers
 270 main.Prepend(CPPPATH=Dir('include'))
 271
 272 if GetOption('verbose'):
 273     def MakeAction(action, string, *args, **kwargs):
 274         return Action(action, *args, **kwargs)
 275 else:
 276     MakeAction = Action
 277     main['CCCOMSTR']        = Transform("CC")
 278     main['CXXCOMSTR']       = Transform("CXX")
 279     main['ASCOMSTR']        = Transform("AS")
 280     main['ARCOMSTR']        = Transform("AR", 0)
 281     main['LINKCOMSTR']      = Transform("LINK", 0)
 282     main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
 283     main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
 284     main['M4COMSTR']        = Transform("M4")
 285     main['SHCCCOMSTR']      = Transform("SHCC")
 286     main['SHCXXCOMSTR']     = Transform("SHCXX")
 287 Export('MakeAction')
 288
 289 # Initialize the Link-Time Optimization (LTO) flags
 290 main['LTO_CCFLAGS'] = []
 291 main['LTO_LDFLAGS'] = []
 292
 293 # According to the readme, tcmalloc works best if the compiler doesn't
 294 # assume that we're using the builtin malloc and friends. These flags
 295 # are compiler-specific, so we need to set them after we detect which
 296 # compiler we're using.
 297 main['TCMALLOC_CCFLAGS'] = []
 298
 299 # Platform-specific configuration.  Note again that we assume that all
 300 # builds under a given build root run on the same host platform.
 301 conf = gem5_scons.Configure(main)
 302
 303 CXX_version = readCommand([main['CXX'],'--version'], exception=False)
 304 CXX_V = readCommand([main['CXX'],'-V'], exception=False)
 305
 306 main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
 307 main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
 308 if main['GCC'] + main['CLANG'] > 1:
 309     error('Two compilers enabled at once?')
 310
 311 # Set up default C++ compiler flags
 312 if main['GCC'] or main['CLANG']:
 313     # As gcc and clang share many flags, do the common parts here
 314     main.Append(CCFLAGS=['-pipe'])
 315     main.Append(CCFLAGS=['-fno-strict-aliasing'])
 316     # Enable -Wall and -Wextra and then disable the few warnings that
 317     # we consistently violate
 318     main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
 319                          '-Wno-sign-compare', '-Wno-unused-parameter'])
 320     # We always compile using C++14
 321     main.Append(CXXFLAGS=['-std=c++14'])
 322     if sys.platform.startswith('freebsd'):
 323         main.Append(CCFLAGS=['-I/usr/local/include'])
 324         main.Append(CXXFLAGS=['-I/usr/local/include'])
 325
 326     # On Mac OS X/Darwin the default linker doesn't support the
 327     # option --as-needed
 328     if sys.platform != "darwin":
 329         main.Append(LINKFLAGS='-Wl,--as-needed')
 330     if GetOption('gold_linker'):
 331         main.Append(LINKFLAGS='-fuse-ld=gold')
 332
 333     # Treat warnings as errors but white list some warnings that we
 334     # want to allow (e.g., deprecation warnings).
 335     main.Append(CCFLAGS=['-Werror',
 336                          '-Wno-error=deprecated-declarations',
 337                          '-Wno-error=deprecated',
 338                         ])
 339 else:
 340     error('\n'.join((
 341           "Don't know what compiler options to use for your compiler.",
 342           "compiler: " + main['CXX'],
 343           "version: " + CXX_version.replace('\n', '<nl>') if
 344                 CXX_version else 'COMMAND NOT FOUND!',
 345           "If you're trying to use a compiler other than GCC",
 346           "or clang, there appears to be something wrong with your",
 347           "environment.",
 348           "",
 349           "If you are trying to use a compiler other than those listed",
 350           "above you will need to ease fix SConstruct and ",
 351           "src/SConscript to support that compiler.")))
 352
 353 if main['GCC']:
 354     gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
 355     if compareVersions(gcc_version, "5") < 0:
 356         error('gcc version 5 or newer required.\n'
 357               'Installed version:', gcc_version)
 358         Exit(1)
 359
 360     main['GCC_VERSION'] = gcc_version
 361
 362     # Add the appropriate Link-Time Optimization (LTO) flags
 363     # unless LTO is explicitly turned off. Note that these flags
 364     # are only used by the fast target.
 365     if not GetOption('no_lto'):
 366         # Pass the LTO flag when compiling to produce GIMPLE
 367         # output, we merely create the flags here and only append
 368         # them later
 369         main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
 370
 371         # Use the same amount of jobs for LTO as we are running
 372         # scons with
 373         main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
 374
 375     main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
 376                                   '-fno-builtin-realloc', '-fno-builtin-free'])
 377
 378 elif main['CLANG']:
 379     clang_version_re = re.compile(".* version (\d+\.\d+)")
 380     clang_version_match = clang_version_re.search(CXX_version)
 381     if (clang_version_match):
 382         clang_version = clang_version_match.groups()[0]
 383         if compareVersions(clang_version, "3.9") < 0:
 384             error('clang version 3.9 or newer required.\n'
 385                   'Installed version:', clang_version)
 386     else:
 387         error('Unable to determine clang version.')
 388
 389     # clang has a few additional warnings that we disable, extraneous
 390     # parantheses are allowed due to Ruby's printing of the AST,
 391     # finally self assignments are allowed as the generated CPU code
 392     # is relying on this
 393     main.Append(CCFLAGS=['-Wno-parentheses',
 394                          '-Wno-self-assign',
 395                          # Some versions of libstdc++ (4.8?) seem to
 396                          # use struct hash and class hash
 397                          # interchangeably.
 398                          '-Wno-mismatched-tags',
 399                          ])
 400     if sys.platform != "darwin" and \
 401        compareVersions(clang_version, "10.0") >= 0:
 402         main.Append(CCFLAGS=['-Wno-c99-designator'])
 403
 404     if compareVersions(clang_version, "8.0") >= 0:
 405         main.Append(CCFLAGS=['-Wno-defaulted-function-deleted'])
 406
 407     main.Append(TCMALLOC_CCFLAGS=['-fno-builtin'])
 408
 409     # On Mac OS X/Darwin we need to also use libc++ (part of XCode) as
 410     # opposed to libstdc++, as the later is dated.
 411     if sys.platform == "darwin":
 412         main.Append(CXXFLAGS=['-stdlib=libc++'])
 413         main.Append(LIBS=['c++'])
 414
 415     # On FreeBSD we need libthr.
 416     if sys.platform.startswith('freebsd'):
 417         main.Append(LIBS=['thr'])
 418
 419 # Add sanitizers flags
 420 sanitizers=[]
 421 if GetOption('with_ubsan'):
 422     sanitizers.append('undefined')
 423 if GetOption('with_asan'):
 424     # Available for gcc >= 5 or llvm >= 3.1 both a requirement
 425     # by the build system
 426     sanitizers.append('address')
 427     suppressions_file = Dir('util').File('lsan-suppressions').get_abspath()
 428     suppressions_opt = 'suppressions=%s' % suppressions_file
 429     main['ENV']['LSAN_OPTIONS'] = ':'.join([suppressions_opt,
 430                                             'print_suppressions=0'])
 431     print()
 432     warning('To suppress false positive leaks, set the LSAN_OPTIONS '
 433             'environment variable to "%s" when running gem5' %
 434             suppressions_opt)
 435     warning('LSAN_OPTIONS=suppressions=%s' % suppressions_opt)
 436     print()
 437 if sanitizers:
 438     sanitizers = ','.join(sanitizers)
 439     if main['GCC'] or main['CLANG']:
 440         main.Append(CCFLAGS=['-fsanitize=%s' % sanitizers,
 441                              '-fno-omit-frame-pointer'],
 442                     LINKFLAGS='-fsanitize=%s' % sanitizers)
 443     else:
 444         warning("Don't know how to enable %s sanitizer(s) for your "
 445                 "compiler." % sanitizers)
 446
 447 # Set up common yacc/bison flags (needed for Ruby)
 448 main['YACCFLAGS'] = '-d'
 449 main['YACCHXXFILESUFFIX'] = '.hh'
 450
 451 # Do this after we save setting back, or else we'll tack on an
 452 # extra 'qdo' every time we run scons.
 453 if main['BATCH']:
 454     main['CC']     = main['BATCH_CMD'] + ' ' + main['CC']
 455     main['CXX']    = main['BATCH_CMD'] + ' ' + main['CXX']
 456     main['AS']     = main['BATCH_CMD'] + ' ' + main['AS']
 457     main['AR']     = main['BATCH_CMD'] + ' ' + main['AR']
 458     main['RANLIB'] = main['BATCH_CMD'] + ' ' + main['RANLIB']
 459
 460 if sys.platform == 'cygwin':
 461     # cygwin has some header file issues...
 462     main.Append(CCFLAGS=["-Wno-uninitialized"])
 463
 464
 465 have_pkg_config = readCommand(['pkg-config', '--version'], exception='')
 466
 467 # Check for the protobuf compiler
 468 try:
 469     main['HAVE_PROTOC'] = True
 470     protoc_version = readCommand([main['PROTOC'], '--version']).split()
 471
 472     # First two words should be "libprotoc x.y.z"
 473     if len(protoc_version) < 2 or protoc_version[0] != 'libprotoc':
 474         warning('Protocol buffer compiler (protoc) not found.\n'
 475                 'Please install protobuf-compiler for tracing support.')
 476         main['HAVE_PROTOC'] = False
 477     else:
 478         # Based on the availability of the compress stream wrappers,
 479         # require 2.1.0
 480         min_protoc_version = '2.1.0'
 481         if compareVersions(protoc_version[1], min_protoc_version) < 0:
 482             warning('protoc version', min_protoc_version,
 483                     'or newer required.\n'
 484                     'Installed version:', protoc_version[1])
 485             main['HAVE_PROTOC'] = False
 486         else:
 487             # Attempt to determine the appropriate include path and
 488             # library path using pkg-config, that means we also need to
 489             # check for pkg-config. Note that it is possible to use
 490             # protobuf without the involvement of pkg-config. Later on we
 491             # check go a library config check and at that point the test
 492             # will fail if libprotobuf cannot be found.
 493             if have_pkg_config:
 494                 try:
 495                     # Attempt to establish what linking flags to add for
 496                     # protobuf
 497                     # using pkg-config
 498                     main.ParseConfig(
 499                             'pkg-config --cflags --libs-only-L protobuf')
 500                 except:
 501                     warning('pkg-config could not get protobuf flags.')
 502 except Exception as e:
 503     warning('While checking protoc version:', str(e))
 504     main['HAVE_PROTOC'] = False
 505
 506
 507 # Cache build files in the supplied directory.
 508 if main['M5_BUILD_CACHE']:
 509     print('Using build cache located at', main['M5_BUILD_CACHE'])
 510     CacheDir(main['M5_BUILD_CACHE'])
 511
 512 if not GetOption('no_compress_debug'):
 513     if not conf.CheckCxxFlag('-gz'):
 514         warning("Can't enable object file debug section compression")
 515     if not conf.CheckLinkFlag('-gz'):
 516         warning("Can't enable executable debug section compression")
 517
 518 main['USE_PYTHON'] = not GetOption('without_python')
 519 if main['USE_PYTHON']:
 520     # Find Python include and library directories for embedding the
 521     # interpreter. We rely on python-config to resolve the appropriate
 522     # includes and linker flags. ParseConfig does not seem to understand
 523     # the more exotic linker flags such as -Xlinker and -export-dynamic so
 524     # we add them explicitly below. If you want to link in an alternate
 525     # version of python, see above for instructions on how to invoke
 526     # scons with the appropriate PATH set.
 527
 528     python_config = main.Detect(main['PYTHON_CONFIG'])
 529     if python_config is None:
 530         error("Can't find a suitable python-config, tried %s" % \
 531               main['PYTHON_CONFIG'])
 532
 533     print("Info: Using Python config: %s" % (python_config, ))
 534
 535     py_includes = readCommand([python_config, '--includes'],
 536                               exception='').split()
 537     py_includes = list(filter(
 538         lambda s: match(r'.*\/include\/.*',s), py_includes))
 539     # Strip the -I from the include folders before adding them to the
 540     # CPPPATH
 541     py_includes = list(map(
 542         lambda s: s[2:] if s.startswith('-I') else s, py_includes))
 543     main.Append(CPPPATH=py_includes)
 544
 545     # Read the linker flags and split them into libraries and other link
 546     # flags. The libraries are added later through the call the CheckLib.
 547     # Note: starting in Python 3.8 the --embed flag is required to get the
 548     # -lpython3.8 linker flag
 549     retcode, cmd_stdout = readCommandWithReturn(
 550         [python_config, '--ldflags', '--embed'], exception='')
 551     if retcode != 0:
 552         # If --embed isn't detected then we're running python <3.8
 553         retcode, cmd_stdout = readCommandWithReturn(
 554             [python_config, '--ldflags'], exception='')
 555
 556     # Checking retcode again
 557     if retcode != 0:
 558         error("Failing on python-config --ldflags command")
 559
 560     py_ld_flags = cmd_stdout.split()
 561
 562     py_libs = []
 563     for lib in py_ld_flags:
 564          if not lib.startswith('-l'):
 565              main.Append(LINKFLAGS=[lib])
 566          else:
 567              lib = lib[2:]
 568              if lib not in py_libs:
 569                  py_libs.append(lib)
 570
 571     # verify that this stuff works
 572     if not conf.CheckHeader('Python.h', '<>'):
 573         error("Check failed for Python.h header in",
 574                 ' '.join(py_includes), "\n"
 575               "Two possible reasons:\n"
 576               "1. Python headers are not installed (You can install the "
 577               "package python-dev on Ubuntu and RedHat)\n"
 578               "2. SCons is using a wrong C compiler. This can happen if "
 579               "CC has the wrong value.\n"
 580               "CC = %s" % main['CC'])
 581
 582     for lib in py_libs:
 583         if not conf.CheckLib(lib):
 584             error("Can't find library %s required by python." % lib)
 585
 586     main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
 587
 588     marshal_env = main.Clone()
 589
 590     # Bare minimum environment that only includes python
 591     marshal_env.Append(CCFLAGS='$MARSHAL_CCFLAGS_EXTRA')
 592     marshal_env.Append(LINKFLAGS='$MARSHAL_LDFLAGS_EXTRA')
 593
 594     py_version = conf.CheckPythonLib()
 595     if not py_version:
 596         error("Can't find a working Python installation")
 597
 598     # Found a working Python installation. Check if it meets minimum
 599     # requirements.
 600     if py_version[0] < 3 or \
 601     (py_version[0] == 3 and py_version[1] < 6):
 602         error('Python version too old. Version 3.6 or newer is required.')
 603     elif py_version[0] > 3:
 604         warning('Python version too new. Python 3 expected.')
 605
 606 # On Solaris you need to use libsocket for socket ops
 607 if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
 608    if not conf.CheckLibWithHeader('socket', 'sys/socket.h',
 609                                   'C++', 'accept(0,0,0);'):
 610        error("Can't find library with socket calls (e.g. accept()).")
 611
 612 # Check for zlib.  If the check passes, libz will be automatically
 613 # added to the LIBS environment variable.
 614 if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
 615     error('Did not find needed zlib compression library '
 616           'and/or zlib.h header file.\n'
 617           'Please install zlib and try again.')
 618
 619 # If we have the protobuf compiler, also make sure we have the
 620 # development libraries. If the check passes, libprotobuf will be
 621 # automatically added to the LIBS environment variable. After
 622 # this, we can use the HAVE_PROTOBUF flag to determine if we have
 623 # got both protoc and libprotobuf available.
 624 main['HAVE_PROTOBUF'] = main['HAVE_PROTOC'] and \
 625     conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
 626                             'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
 627
 628 # Valgrind gets much less confused if you tell it when you're using
 629 # alternative stacks.
 630 main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
 631
 632 # If we have the compiler but not the library, print another warning.
 633 if main['HAVE_PROTOC'] and not main['HAVE_PROTOBUF']:
 634     warning('Did not find protocol buffer library and/or headers.\n'
 635             'Please install libprotobuf-dev for tracing support.')
 636
 637 # Check for librt.
 638 have_posix_clock = \
 639     conf.CheckLibWithHeader(None, 'time.h', 'C',
 640                             'clock_nanosleep(0,0,NULL,NULL);') or \
 641     conf.CheckLibWithHeader('rt', 'time.h', 'C',
 642                             'clock_nanosleep(0,0,NULL,NULL);')
 643
 644 have_posix_timers = \
 645     conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
 646                             'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
 647
 648 if not GetOption('without_tcmalloc'):
 649     if conf.CheckLib('tcmalloc'):
 650         main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
 651     elif conf.CheckLib('tcmalloc_minimal'):
 652         main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
 653     else:
 654         warning("You can get a 12% performance improvement by "
 655                 "installing tcmalloc (libgoogle-perftools-dev package "
 656                 "on Ubuntu or RedHat).")
 657
 658
 659 # Detect back trace implementations. The last implementation in the
 660 # list will be used by default.
 661 backtrace_impls = [ "none" ]
 662
 663 backtrace_checker = 'char temp;' + \
 664     ' backtrace_symbols_fd((void*)&temp, 0, 0);'
 665 if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
 666     backtrace_impls.append("glibc")
 667 elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
 668                              backtrace_checker):
 669     # NetBSD and FreeBSD need libexecinfo.
 670     backtrace_impls.append("glibc")
 671     main.Append(LIBS=['execinfo'])
 672
 673 if backtrace_impls[-1] == "none":
 674     default_backtrace_impl = "none"
 675     warning("No suitable back trace implementation found.")
 676
 677 if not have_posix_clock:
 678     warning("Can't find library for POSIX clocks.")
 679
 680 # Check for <fenv.h> (C99 FP environment control)
 681 have_fenv = conf.CheckHeader('fenv.h', '<>')
 682 if not have_fenv:
 683     warning("Header file <fenv.h> not found.\n"
 684             "This host has no IEEE FP rounding mode control.")
 685
 686 # Check for <png.h> (libpng library needed if wanting to dump
 687 # frame buffer image in png format)
 688 have_png = conf.CheckHeader('png.h', '<>')
 689 if not have_png:
 690     warning("Header file <png.h> not found.\n"
 691             "This host has no libpng library.\n"
 692             "Disabling support for PNG framebuffers.")
 693
 694 # Check if we should enable KVM-based hardware virtualization. The API
 695 # we rely on exists since version 2.6.36 of the kernel, but somehow
 696 # the KVM_API_VERSION does not reflect the change. We test for one of
 697 # the types as a fall back.
 698 have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
 699 if not have_kvm:
 700     print("Info: Compatible header file <linux/kvm.h> not found, "
 701           "disabling KVM support.")
 702
 703 # Check if the TUN/TAP driver is available.
 704 have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
 705 if not have_tuntap:
 706     print("Info: Compatible header file <linux/if_tun.h> not found.")
 707
 708 # x86 needs support for xsave. We test for the structure here since we
 709 # won't be able to run new tests by the time we know which ISA we're
 710 # targeting.
 711 have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
 712                                     '#include <linux/kvm.h>') != 0
 713
 714 # Check if the requested target ISA is compatible with the host
 715 def is_isa_kvm_compatible(isa):
 716     try:
 717         import platform
 718         host_isa = platform.machine()
 719     except:
 720         warning("Failed to determine host ISA.")
 721         return False
 722
 723     if not have_posix_timers:
 724         warning("Can not enable KVM, host seems to lack support "
 725                 "for POSIX timers")
 726         return False
 727
 728     if isa == "arm":
 729         return host_isa in ( "armv7l", "aarch64" )
 730     elif isa == "x86":
 731         if host_isa != "x86_64":
 732             return False
 733
 734         if not have_kvm_xsave:
 735             warning("KVM on x86 requires xsave support in kernel headers.")
 736             return False
 737
 738         return True
 739     else:
 740         return False
 741
 742
 743 # Check if the exclude_host attribute is available. We want this to
 744 # get accurate instruction counts in KVM.
 745 main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
 746     'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
 747
 748 def check_hdf5():
 749     return \
 750         conf.CheckLibWithHeader('hdf5', 'hdf5.h', 'C',
 751                                 'H5Fcreate("", 0, 0, 0);') and \
 752         conf.CheckLibWithHeader('hdf5_cpp', 'H5Cpp.h', 'C++',
 753                                 'H5::H5File("", 0);')
 754
 755 def check_hdf5_pkg(name):
 756     print("Checking for %s using pkg-config..." % name, end="")
 757     if not have_pkg_config:
 758         print(" pkg-config not found")
 759         return False
 760
 761     try:
 762         main.ParseConfig('pkg-config --cflags-only-I --libs-only-L %s' % name)
 763         print(" yes")
 764         return True
 765     except:
 766         print(" no")
 767         return False
 768
 769 # Check if there is a pkg-config configuration for hdf5. If we find
 770 # it, setup the environment to enable linking and header inclusion. We
 771 # don't actually try to include any headers or link with hdf5 at this
 772 # stage.
 773 if not check_hdf5_pkg('hdf5-serial'):
 774     check_hdf5_pkg('hdf5')
 775
 776 # Check if the HDF5 libraries can be found. This check respects the
 777 # include path and library path provided by pkg-config. We perform
 778 # this check even if there isn't a pkg-config configuration for hdf5
 779 # since some installations don't use pkg-config.
 780 have_hdf5 = check_hdf5()
 781 if not have_hdf5:
 782     print("Warning: Couldn't find any HDF5 C++ libraries. Disabling")
 783     print("         HDF5 support.")
 784
 785 ######################################################################
 786 #
 787 # Finish the configuration
 788 #
 789 main = conf.Finish()
 790
 791 ######################################################################
 792 #
 793 # Collect all non-global variables
 794 #
 795
 796 # Define the universe of supported ISAs
 797 all_isa_list = [ ]
 798 all_gpu_isa_list = [ ]
 799 Export('all_isa_list')
 800 Export('all_gpu_isa_list')
 801
 802 class CpuModel(object):
 803     '''The CpuModel class encapsulates everything the ISA parser needs to
 804     know about a particular CPU model.'''
 805
 806     # Dict of available CPU model objects.  Accessible as CpuModel.dict.
 807     dict = {}
 808
 809     # Constructor.  Automatically adds models to CpuModel.dict.
 810     def __init__(self, name, default=False):
 811         self.name = name           # name of model
 812
 813         # This cpu is enabled by default
 814         self.default = default
 815
 816         # Add self to dict
 817         if name in CpuModel.dict:
 818             raise AttributeError("CpuModel '%s' already registered" % name)
 819         CpuModel.dict[name] = self
 820
 821 Export('CpuModel')
 822
 823 # Sticky variables get saved in the variables file so they persist from
 824 # one invocation to the next (unless overridden, in which case the new
 825 # value becomes sticky).
 826 sticky_vars = Variables(args=ARGUMENTS)
 827 Export('sticky_vars')
 828
 829 # Sticky variables that should be exported
 830 export_vars = []
 831 Export('export_vars')
 832
 833 # For Ruby
 834 all_protocols = []
 835 Export('all_protocols')
 836 protocol_dirs = []
 837 Export('protocol_dirs')
 838 slicc_includes = []
 839 Export('slicc_includes')
 840
 841 # Walk the tree and execute all SConsopts scripts that wil add to the
 842 # above variables
 843 if GetOption('verbose'):
 844     print("Reading SConsopts")
 845 for bdir in [ base_dir ] + extras_dir_list:
 846     if not isdir(bdir):
 847         error("Directory '%s' does not exist." % bdir)
 848     for root, dirs, files in os.walk(bdir):
 849         if 'SConsopts' in files:
 850             if GetOption('verbose'):
 851                 print("Reading", joinpath(root, 'SConsopts'))
 852             SConscript(joinpath(root, 'SConsopts'))
 853
 854 all_isa_list.sort()
 855 all_gpu_isa_list.sort()
 856
 857 sticky_vars.AddVariables(
 858     EnumVariable('TARGET_ISA', 'Target ISA', 'null', all_isa_list),
 859     EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'gcn3', all_gpu_isa_list),
 860     ListVariable('CPU_MODELS', 'CPU models',
 861                  sorted(n for n,m in CpuModel.dict.items() if m.default),
 862                  sorted(CpuModel.dict.keys())),
 863     BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
 864                  False),
 865     BoolVariable('USE_SSE2',
 866                  'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
 867                  False),
 868     BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
 869     BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
 870     BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
 871     BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
 872                  have_kvm),
 873     BoolVariable('USE_TUNTAP',
 874                  'Enable using a tap device to bridge to the host network',
 875                  have_tuntap),
 876     BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
 877     EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
 878                   all_protocols),
 879     EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
 880                  backtrace_impls[-1], backtrace_impls),
 881     ('NUMBER_BITS_PER_SET', 'Max elements in set (default 64)',
 882                  64),
 883     BoolVariable('USE_HDF5', 'Enable the HDF5 support', have_hdf5),
 884     )
 885
 886 # These variables get exported to #defines in config/*.hh (see src/SConscript).
 887 export_vars += ['USE_FENV', 'TARGET_ISA', 'TARGET_GPU_ISA',
 888                 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP', 'PROTOCOL',
 889                 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
 890                 'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG',
 891                 'NUMBER_BITS_PER_SET', 'USE_HDF5']
 892
 893 ###################################################
 894 #
 895 # Define a SCons builder for configuration flag headers.
 896 #
 897 ###################################################
 898
 899 # This function generates a config header file that #defines the
 900 # variable symbol to the current variable setting (0 or 1).  The source
 901 # operands are the name of the variable and a Value node containing the
 902 # value of the variable.
 903 def build_config_file(target, source, env):
 904     (variable, value) = [s.get_contents().decode('utf-8') for s in source]
 905     with open(str(target[0].abspath), 'w') as f:
 906         print('#define', variable, value, file=f)
 907     return None
 908
 909 # Combine the two functions into a scons Action object.
 910 config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
 911
 912 # The emitter munges the source & target node lists to reflect what
 913 # we're really doing.
 914 def config_emitter(target, source, env):
 915     # extract variable name from Builder arg
 916     variable = str(target[0])
 917     # True target is config header file
 918     target = Dir('config').File(variable.lower() + '.hh')
 919     val = env[variable]
 920     if isinstance(val, bool):
 921         # Force value to 0/1
 922         val = int(val)
 923     elif isinstance(val, str):
 924         val = '"' + val + '"'
 925
 926     # Sources are variable name & value (packaged in SCons Value nodes)
 927     return [target], [Value(variable), Value(val)]
 928
 929 config_builder = Builder(emitter=config_emitter, action=config_action)
 930
 931 main.Append(BUILDERS = { 'ConfigFile' : config_builder })
 932
 933 def add_local_rpath(env, *targets):
 934     '''Set up an RPATH for a library which lives in the build directory.
 935
 936     The construction environment variable BIN_RPATH_PREFIX should be set to
 937     the relative path of the build directory starting from the location of the
 938     binary.'''
 939     for target in targets:
 940         target = env.Entry(target)
 941         if not isinstance(target, SCons.Node.FS.Dir):
 942             target = target.dir
 943         relpath = os.path.relpath(target.abspath, env['BUILDDIR'])
 944         components = [
 945             '\\$$ORIGIN',
 946             '${BIN_RPATH_PREFIX}',
 947             relpath
 948         ]
 949         env.Append(RPATH=[env.Literal(os.path.join(*components))])
 950
 951 if sys.platform != "darwin":
 952     main.Append(LINKFLAGS=Split('-z origin'))
 953
 954 main.AddMethod(add_local_rpath, 'AddLocalRPATH')
 955
 956 # builds in ext are shared across all configs in the build root.
 957 ext_dir = Dir('#ext').abspath
 958 ext_build_dirs = []
 959 for root, dirs, files in os.walk(ext_dir):
 960     if 'SConscript' in files:
 961         build_dir = os.path.relpath(root, ext_dir)
 962         ext_build_dirs.append(build_dir)
 963         main.SConscript(joinpath(root, 'SConscript'),
 964                         variant_dir=joinpath(build_root, build_dir))
 965
 966 gdb_xml_dir = joinpath(ext_dir, 'gdb-xml')
 967 Export('gdb_xml_dir')
 968
 969 ###################################################
 970 #
 971 # This builder and wrapper method are used to set up a directory with
 972 # switching headers. Those are headers which are in a generic location and
 973 # that include more specific headers from a directory chosen at build time
 974 # based on the current build settings.
 975 #
 976 ###################################################
 977
 978 def build_switching_header(target, source, env):
 979     path = str(target[0])
 980     subdir = str(source[0])
 981     dp, fp = os.path.split(path)
 982     dp = os.path.relpath(os.path.realpath(dp),
 983                          os.path.realpath(env['BUILDDIR']))
 984     with open(path, 'w') as hdr:
 985         print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
 986
 987 switching_header_action = MakeAction(build_switching_header,
 988                                      Transform('GENERATE'))
 989
 990 switching_header_builder = Builder(action=switching_header_action,
 991                                    source_factory=Value,
 992                                    single_source=True)
 993
 994 main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
 995
 996 def switching_headers(self, headers, source):
 997     for header in headers:
 998         self.SwitchingHeader(header, source)
 999
1000 main.AddMethod(switching_headers, 'SwitchingHeaders')
1001
1002 ###################################################
1003 #
1004 # Define build environments for selected configurations.
1005 #
1006 ###################################################
1007
1008 for variant_path in variant_paths:
1009     if not GetOption('silent'):
1010         print("Building in", variant_path)
1011
1012     # Make a copy of the build-root environment to use for this config.
1013     env = main.Clone()
1014     env['BUILDDIR'] = variant_path
1015
1016     # variant_dir is the tail component of build path, and is used to
1017     # determine the build parameters (e.g., 'X86')
1018     (build_root, variant_dir) = splitpath(variant_path)
1019
1020     # Set env variables according to the build directory config.
1021     sticky_vars.files = []
1022     # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1023     # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1024     # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1025     current_vars_file = joinpath(build_root, 'variables', variant_dir)
1026     if isfile(current_vars_file):
1027         sticky_vars.files.append(current_vars_file)
1028         if not GetOption('silent'):
1029             print("Using saved variables file %s" % current_vars_file)
1030     elif variant_dir in ext_build_dirs:
1031         # Things in ext are built without a variant directory.
1032         continue
1033     else:
1034         # Build dir-specific variables file doesn't exist.
1035
1036         # Make sure the directory is there so we can create it later
1037         opt_dir = dirname(current_vars_file)
1038         if not isdir(opt_dir):
1039             mkdir(opt_dir)
1040
1041         # Get default build variables from source tree.  Variables are
1042         # normally determined by name of $VARIANT_DIR, but can be
1043         # overridden by '--default=' arg on command line.
1044         default = GetOption('default')
1045         opts_dir = Dir('#build_opts').abspath
1046         if default:
1047             default_vars_files = [joinpath(build_root, 'variables', default),
1048                                   joinpath(opts_dir, default)]
1049         else:
1050             default_vars_files = [joinpath(opts_dir, variant_dir)]
1051         existing_files = list(filter(isfile, default_vars_files))
1052         if existing_files:
1053             default_vars_file = existing_files[0]
1054             sticky_vars.files.append(default_vars_file)
1055             print("Variables file %s not found,\n  using defaults in %s"
1056                   % (current_vars_file, default_vars_file))
1057         else:
1058             error("Cannot find variables file %s or default file(s) %s"
1059                   % (current_vars_file, ' or '.join(default_vars_files)))
1060             Exit(1)
1061
1062     # Apply current variable settings to env
1063     sticky_vars.Update(env)
1064
1065     Help('''
1066 Build variables for {dir}:
1067 {help}
1068 '''.format(dir=variant_dir, help=sticky_vars.GenerateHelpText(env)),
1069          append=True)
1070
1071     # Process variable settings.
1072
1073     if not have_fenv and env['USE_FENV']:
1074         warning("<fenv.h> not available; forcing USE_FENV to False in",
1075                 variant_dir + ".")
1076         env['USE_FENV'] = False
1077
1078     if not env['USE_FENV']:
1079         warning("No IEEE FP rounding mode control in", variant_dir + ".\n"
1080                 "FP results may deviate slightly from other platforms.")
1081
1082     if not have_png and env['USE_PNG']:
1083         warning("<png.h> not available; forcing USE_PNG to False in",
1084                 variant_dir + ".")
1085         env['USE_PNG'] = False
1086
1087     if env['USE_PNG']:
1088         env.Append(LIBS=['png'])
1089
1090     if env['EFENCE']:
1091         env.Append(LIBS=['efence'])
1092
1093     if env['USE_KVM']:
1094         if not have_kvm:
1095             warning("Can not enable KVM, host seems to lack KVM support")
1096             env['USE_KVM'] = False
1097         elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1098             print("Info: KVM support disabled due to unsupported host and "
1099                   "target ISA combination")
1100             env['USE_KVM'] = False
1101
1102     if env['USE_TUNTAP']:
1103         if not have_tuntap:
1104             warning("Can't connect EtherTap with a tap device.")
1105             env['USE_TUNTAP'] = False
1106
1107     if env['BUILD_GPU']:
1108         env.Append(CPPDEFINES=['BUILD_GPU'])
1109
1110     # Warn about missing optional functionality
1111     if env['USE_KVM']:
1112         if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1113             warning("perf_event headers lack support for the exclude_host "
1114                     "attribute. KVM instruction counts will be inaccurate.")
1115
1116     # Save sticky variable settings back to current variables file
1117     sticky_vars.Save(current_vars_file, env)
1118
1119     if env['USE_SSE2']:
1120         env.Append(CCFLAGS=['-msse2'])
1121
1122     env.Append(CCFLAGS='$CCFLAGS_EXTRA')
1123     env.Append(LINKFLAGS='$LDFLAGS_EXTRA')
1124
1125     exports=['env']
1126     if main['USE_PYTHON']:
1127         exports.append('marshal_env')
1128
1129     # The src/SConscript file sets up the build rules in 'env' according
1130     # to the configured variables.  It returns a list of environments,
1131     # one for each variant build (debug, opt, etc.)
1132     SConscript('src/SConscript', variant_dir=variant_path, exports=exports)
1133
1134 atexit.register(summarize_warnings)