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-lto', action='store_true',
 112           help='Disable Link-Time Optimization for fast')
 113 AddOption('--force-lto', action='store_true',
 114           help='Use Link-Time Optimization instead of partial linking' +
 115                ' when the compiler doesn\'t support using them together.')
 116 AddOption('--verbose', action='store_true',
 117           help='Print full tool command lines')
 118 AddOption('--without-python', action='store_true',
 119           help='Build without Python configuration support')
 120 AddOption('--without-tcmalloc', action='store_true',
 121           help='Disable linking against tcmalloc')
 122 AddOption('--with-ubsan', action='store_true',
 123           help='Build with Undefined Behavior Sanitizer if available')
 124 AddOption('--with-asan', action='store_true',
 125           help='Build with Address Sanitizer if available')
 126 AddOption('--with-systemc-tests', action='store_true',
 127           help='Build systemc tests')
 128
 129 from gem5_scons import Transform, error, warning, summarize_warnings
 130
 131 if GetOption('no_lto') and GetOption('force_lto'):
 132     error('--no-lto and --force-lto are mutually exclusive')
 133
 134 ########################################################################
 135 #
 136 # Set up the main build environment.
 137 #
 138 ########################################################################
 139
 140 main = Environment(tools=['default', 'git'])
 141
 142 from gem5_scons.util import get_termcap
 143 termcap = get_termcap()
 144
 145 main_dict_keys = main.Dictionary().keys()
 146
 147 # Check that we have a C/C++ compiler
 148 if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
 149     error("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
 150
 151 ###################################################
 152 #
 153 # Figure out which configurations to set up based on the path(s) of
 154 # the target(s).
 155 #
 156 ###################################################
 157
 158 # Find default configuration & binary.
 159 Default(environ.get('M5_DEFAULT_BINARY', 'build/ARM/gem5.debug'))
 160
 161 # helper function: find last occurrence of element in list
 162 def rfind(l, elt, offs = -1):
 163     for i in range(len(l)+offs, 0, -1):
 164         if l[i] == elt:
 165             return i
 166     raise ValueError("element not found")
 167
 168 # Take a list of paths (or SCons Nodes) and return a list with all
 169 # paths made absolute and ~-expanded.  Paths will be interpreted
 170 # relative to the launch directory unless a different root is provided
 171 def makePathListAbsolute(path_list, root=GetLaunchDir()):
 172     return [abspath(joinpath(root, expanduser(str(p))))
 173             for p in path_list]
 174
 175 # Each target must have 'build' in the interior of the path; the
 176 # directory below this will determine the build parameters.  For
 177 # example, for target 'foo/bar/build/X86/arch/x86/blah.do' we
 178 # recognize that X86 specifies the configuration because it
 179 # follow 'build' in the build path.
 180
 181 # The funky assignment to "[:]" is needed to replace the list contents
 182 # in place rather than reassign the symbol to a new list, which
 183 # doesn't work (obviously!).
 184 BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
 185
 186 # Generate a list of the unique build roots and configs that the
 187 # collected targets reference.
 188 variant_paths = []
 189 build_root = None
 190 for t in BUILD_TARGETS:
 191     path_dirs = t.split('/')
 192     try:
 193         build_top = rfind(path_dirs, 'build', -2)
 194     except:
 195         error("No non-leaf 'build' dir found on target path.", t)
 196     this_build_root = joinpath('/',*path_dirs[:build_top+1])
 197     if not build_root:
 198         build_root = this_build_root
 199     else:
 200         if this_build_root != build_root:
 201             error("build targets not under same build root\n"
 202                   "  %s\n  %s" % (build_root, this_build_root))
 203     variant_path = joinpath('/',*path_dirs[:build_top+2])
 204     if variant_path not in variant_paths:
 205         variant_paths.append(variant_path)
 206
 207 # Make sure build_root exists (might not if this is the first build there)
 208 if not isdir(build_root):
 209     mkdir(build_root)
 210 main['BUILDROOT'] = build_root
 211
 212 Export('main')
 213
 214 main.SConsignFile(joinpath(build_root, "sconsign"))
 215
 216 # Default duplicate option is to use hard links, but this messes up
 217 # when you use emacs to edit a file in the target dir, as emacs moves
 218 # file to file~ then copies to file, breaking the link.  Symbolic
 219 # (soft) links work better.
 220 main.SetOption('duplicate', 'soft-copy')
 221
 222 #
 223 # Set up global sticky variables... these are common to an entire build
 224 # tree (not specific to a particular build like X86)
 225 #
 226
 227 global_vars_file = joinpath(build_root, 'variables.global')
 228
 229 global_vars = Variables(global_vars_file, args=ARGUMENTS)
 230
 231 global_vars.AddVariables(
 232     ('CC', 'C compiler', environ.get('CC', main['CC'])),
 233     ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
 234     ('CCFLAGS_EXTRA', 'Extra C and C++ compiler flags', ''),
 235     ('LDFLAGS_EXTRA', 'Extra linker flags', ''),
 236     ('MARSHAL_CCFLAGS_EXTRA', 'Extra C and C++ marshal compiler flags', ''),
 237     ('MARSHAL_LDFLAGS_EXTRA', 'Extra marshal linker flags', ''),
 238     ('PYTHON_CONFIG', 'Python config binary to use',
 239      [ 'python3-config', 'python-config']
 240     ),
 241     ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
 242     ('BATCH', 'Use batch pool for build and tests', False),
 243     ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
 244     ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
 245     ('EXTRAS', 'Add extra directories to the compilation', '')
 246     )
 247
 248 # Update main environment with values from ARGUMENTS & global_vars_file
 249 global_vars.Update(main)
 250 Help('''
 251 Global build variables:
 252 {help}
 253 '''.format(help=global_vars.GenerateHelpText(main)), append=True)
 254
 255 # Save sticky variable settings back to current variables file
 256 global_vars.Save(global_vars_file, main)
 257
 258 # Parse EXTRAS variable to build list of all directories where we're
 259 # look for sources etc.  This list is exported as extras_dir_list.
 260 base_dir = Dir('#src').abspath
 261 if main['EXTRAS']:
 262     extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
 263 else:
 264     extras_dir_list = []
 265
 266 Export('base_dir')
 267 Export('extras_dir_list')
 268
 269 # the ext directory should be on the #includes path
 270 main.Append(CPPPATH=[Dir('ext')])
 271
 272 # Add shared top-level headers
 273 main.Prepend(CPPPATH=Dir('include'))
 274
 275 if GetOption('verbose'):
 276     def MakeAction(action, string, *args, **kwargs):
 277         return Action(action, *args, **kwargs)
 278 else:
 279     MakeAction = Action
 280     main['CCCOMSTR']        = Transform("CC")
 281     main['CXXCOMSTR']       = Transform("CXX")
 282     main['ASCOMSTR']        = Transform("AS")
 283     main['ARCOMSTR']        = Transform("AR", 0)
 284     main['LINKCOMSTR']      = Transform("LINK", 0)
 285     main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
 286     main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
 287     main['M4COMSTR']        = Transform("M4")
 288     main['SHCCCOMSTR']      = Transform("SHCC")
 289     main['SHCXXCOMSTR']     = Transform("SHCXX")
 290 Export('MakeAction')
 291
 292 # Initialize the Link-Time Optimization (LTO) flags
 293 main['LTO_CCFLAGS'] = []
 294 main['LTO_LDFLAGS'] = []
 295
 296 # According to the readme, tcmalloc works best if the compiler doesn't
 297 # assume that we're using the builtin malloc and friends. These flags
 298 # are compiler-specific, so we need to set them after we detect which
 299 # compiler we're using.
 300 main['TCMALLOC_CCFLAGS'] = []
 301
 302 CXX_version = readCommand([main['CXX'],'--version'], exception=False)
 303 CXX_V = readCommand([main['CXX'],'-V'], exception=False)
 304
 305 main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
 306 main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
 307 if main['GCC'] + main['CLANG'] > 1:
 308     error('Two compilers enabled at once?')
 309
 310 # Set up default C++ compiler flags
 311 if main['GCC'] or main['CLANG']:
 312     # As gcc and clang share many flags, do the common parts here
 313     main.Append(CCFLAGS=['-pipe'])
 314     main.Append(CCFLAGS=['-fno-strict-aliasing'])
 315     # Enable -Wall and -Wextra and then disable the few warnings that
 316     # we consistently violate
 317     main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
 318                          '-Wno-sign-compare', '-Wno-unused-parameter'])
 319     # We always compile using C++14
 320     main.Append(CXXFLAGS=['-std=c++14'])
 321     if sys.platform.startswith('freebsd'):
 322         main.Append(CCFLAGS=['-I/usr/local/include'])
 323         main.Append(CXXFLAGS=['-I/usr/local/include'])
 324
 325     # On Mac OS X/Darwin the default linker doesn't support the
 326     # option --as-needed
 327     if sys.platform != "darwin":
 328         main.Append(LINKFLAGS='-Wl,--as-needed')
 329     main['FILTER_PSHLINKFLAGS'] = lambda x: str(x).replace(' -shared', '')
 330     main['PSHLINKFLAGS'] = main.subst('${FILTER_PSHLINKFLAGS(SHLINKFLAGS)}')
 331     if GetOption('gold_linker'):
 332         main.Append(LINKFLAGS='-fuse-ld=gold')
 333     main['PLINKFLAGS'] = main.get('LINKFLAGS')
 334     shared_partial_flags = ['-r', '-nostdlib']
 335     main.Append(PSHLINKFLAGS=shared_partial_flags)
 336     main.Append(PLINKFLAGS=shared_partial_flags)
 337
 338     # Treat warnings as errors but white list some warnings that we
 339     # want to allow (e.g., deprecation warnings).
 340     main.Append(CCFLAGS=['-Werror',
 341                          '-Wno-error=deprecated-declarations',
 342                          '-Wno-error=deprecated',
 343                         ])
 344 else:
 345     error('\n'.join((
 346           "Don't know what compiler options to use for your compiler.",
 347           "compiler: " + main['CXX'],
 348           "version: " + CXX_version.replace('\n', '<nl>') if
 349                 CXX_version else 'COMMAND NOT FOUND!',
 350           "If you're trying to use a compiler other than GCC",
 351           "or clang, there appears to be something wrong with your",
 352           "environment.",
 353           "",
 354           "If you are trying to use a compiler other than those listed",
 355           "above you will need to ease fix SConstruct and ",
 356           "src/SConscript to support that compiler.")))
 357
 358 if main['GCC']:
 359     gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
 360     if compareVersions(gcc_version, "5") < 0:
 361         error('gcc version 5 or newer required.\n'
 362               'Installed version:', gcc_version)
 363         Exit(1)
 364
 365     main['GCC_VERSION'] = gcc_version
 366
 367     # Incremental linking with LTO is currently broken in gcc versions
 368     # 4.9 and above. A version where everything works completely hasn't
 369     # yet been identified.
 370     #
 371     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548
 372     main['BROKEN_INCREMENTAL_LTO'] = True
 373
 374     if compareVersions(gcc_version, '6.0') >= 0:
 375         # gcc versions 6.0 and greater accept an -flinker-output flag which
 376         # selects what type of output the linker should generate. This is
 377         # necessary for incremental lto to work, but is also broken in
 378         # current versions of gcc. It may not be necessary in future
 379         # versions. We add it here since it might be, and as a reminder that
 380         # it exists. It's excluded if lto is being forced.
 381         #
 382         # https://gcc.gnu.org/gcc-6/changes.html
 383         # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html
 384         # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866
 385         if not GetOption('force_lto'):
 386             main.Append(PSHLINKFLAGS='-flinker-output=rel')
 387             main.Append(PLINKFLAGS='-flinker-output=rel')
 388
 389     disable_lto = GetOption('no_lto')
 390     if not disable_lto and main.get('BROKEN_INCREMENTAL_LTO', False) and \
 391             not GetOption('force_lto'):
 392         warning('Your compiler doesn\'t support incremental linking and lto '
 393                 'at the same time, so lto is being disabled. To force lto on '
 394                 'anyway, use the --force-lto option. That will disable '
 395                 'partial linking.')
 396         disable_lto = True
 397
 398     # Add the appropriate Link-Time Optimization (LTO) flags
 399     # unless LTO is explicitly turned off. Note that these flags
 400     # are only used by the fast target.
 401     if not disable_lto:
 402         # Pass the LTO flag when compiling to produce GIMPLE
 403         # output, we merely create the flags here and only append
 404         # them later
 405         main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
 406
 407         # Use the same amount of jobs for LTO as we are running
 408         # scons with
 409         main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
 410
 411     main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
 412                                   '-fno-builtin-realloc', '-fno-builtin-free'])
 413
 414 elif main['CLANG']:
 415     clang_version_re = re.compile(".* version (\d+\.\d+)")
 416     clang_version_match = clang_version_re.search(CXX_version)
 417     if (clang_version_match):
 418         clang_version = clang_version_match.groups()[0]
 419         if compareVersions(clang_version, "3.9") < 0:
 420             error('clang version 3.9 or newer required.\n'
 421                   'Installed version:', clang_version)
 422     else:
 423         error('Unable to determine clang version.')
 424
 425     # clang has a few additional warnings that we disable, extraneous
 426     # parantheses are allowed due to Ruby's printing of the AST,
 427     # finally self assignments are allowed as the generated CPU code
 428     # is relying on this
 429     main.Append(CCFLAGS=['-Wno-parentheses',
 430                          '-Wno-self-assign',
 431                          # Some versions of libstdc++ (4.8?) seem to
 432                          # use struct hash and class hash
 433                          # interchangeably.
 434                          '-Wno-mismatched-tags',
 435                          ])
 436     if sys.platform != "darwin" and \
 437        compareVersions(clang_version, "10.0") >= 0:
 438         main.Append(CCFLAGS=['-Wno-c99-designator'])
 439
 440     if compareVersions(clang_version, "8.0") >= 0:
 441         main.Append(CCFLAGS=['-Wno-defaulted-function-deleted'])
 442
 443     main.Append(TCMALLOC_CCFLAGS=['-fno-builtin'])
 444
 445     # On Mac OS X/Darwin we need to also use libc++ (part of XCode) as
 446     # opposed to libstdc++, as the later is dated.
 447     if sys.platform == "darwin":
 448         main.Append(CXXFLAGS=['-stdlib=libc++'])
 449         main.Append(LIBS=['c++'])
 450
 451     # On FreeBSD we need libthr.
 452     if sys.platform.startswith('freebsd'):
 453         main.Append(LIBS=['thr'])
 454
 455 # Add sanitizers flags
 456 sanitizers=[]
 457 if GetOption('with_ubsan'):
 458     sanitizers.append('undefined')
 459 if GetOption('with_asan'):
 460     # Available for gcc >= 5 or llvm >= 3.1 both a requirement
 461     # by the build system
 462     sanitizers.append('address')
 463     suppressions_file = Dir('util').File('lsan-suppressions').get_abspath()
 464     suppressions_opt = 'suppressions=%s' % suppressions_file
 465     main['ENV']['LSAN_OPTIONS'] = ':'.join([suppressions_opt,
 466                                             'print_suppressions=0'])
 467     print()
 468     warning('To suppress false positive leaks, set the LSAN_OPTIONS '
 469             'environment variable to "%s" when running gem5' %
 470             suppressions_opt)
 471     warning('LSAN_OPTIONS=suppressions=%s' % suppressions_opt)
 472     print()
 473 if sanitizers:
 474     sanitizers = ','.join(sanitizers)
 475     if main['GCC'] or main['CLANG']:
 476         main.Append(CCFLAGS=['-fsanitize=%s' % sanitizers,
 477                              '-fno-omit-frame-pointer'],
 478                     LINKFLAGS='-fsanitize=%s' % sanitizers)
 479     else:
 480         warning("Don't know how to enable %s sanitizer(s) for your "
 481                 "compiler." % sanitizers)
 482
 483 # Set up common yacc/bison flags (needed for Ruby)
 484 main['YACCFLAGS'] = '-d'
 485 main['YACCHXXFILESUFFIX'] = '.hh'
 486
 487 # Do this after we save setting back, or else we'll tack on an
 488 # extra 'qdo' every time we run scons.
 489 if main['BATCH']:
 490     main['CC']     = main['BATCH_CMD'] + ' ' + main['CC']
 491     main['CXX']    = main['BATCH_CMD'] + ' ' + main['CXX']
 492     main['AS']     = main['BATCH_CMD'] + ' ' + main['AS']
 493     main['AR']     = main['BATCH_CMD'] + ' ' + main['AR']
 494     main['RANLIB'] = main['BATCH_CMD'] + ' ' + main['RANLIB']
 495
 496 if sys.platform == 'cygwin':
 497     # cygwin has some header file issues...
 498     main.Append(CCFLAGS=["-Wno-uninitialized"])
 499
 500
 501 have_pkg_config = readCommand(['pkg-config', '--version'], exception='')
 502
 503 # Check for the protobuf compiler
 504 try:
 505     main['HAVE_PROTOC'] = True
 506     protoc_version = readCommand([main['PROTOC'], '--version']).split()
 507
 508     # First two words should be "libprotoc x.y.z"
 509     if len(protoc_version) < 2 or protoc_version[0] != 'libprotoc':
 510         warning('Protocol buffer compiler (protoc) not found.\n'
 511                 'Please install protobuf-compiler for tracing support.')
 512         main['HAVE_PROTOC'] = False
 513     else:
 514         # Based on the availability of the compress stream wrappers,
 515         # require 2.1.0
 516         min_protoc_version = '2.1.0'
 517         if compareVersions(protoc_version[1], min_protoc_version) < 0:
 518             warning('protoc version', min_protoc_version,
 519                     'or newer required.\n'
 520                     'Installed version:', protoc_version[1])
 521             main['HAVE_PROTOC'] = False
 522         else:
 523             # Attempt to determine the appropriate include path and
 524             # library path using pkg-config, that means we also need to
 525             # check for pkg-config. Note that it is possible to use
 526             # protobuf without the involvement of pkg-config. Later on we
 527             # check go a library config check and at that point the test
 528             # will fail if libprotobuf cannot be found.
 529             if have_pkg_config:
 530                 try:
 531                     # Attempt to establish what linking flags to add for
 532                     # protobuf
 533                     # using pkg-config
 534                     main.ParseConfig(
 535                             'pkg-config --cflags --libs-only-L protobuf')
 536                 except:
 537                     warning('pkg-config could not get protobuf flags.')
 538 except Exception as e:
 539     warning('While checking protoc version:', str(e))
 540     main['HAVE_PROTOC'] = False
 541
 542 # Check for 'timeout' from GNU coreutils. If present, regressions will
 543 # be run with a time limit. We require version 8.13 since we rely on
 544 # support for the '--foreground' option.
 545 if sys.platform.startswith('freebsd'):
 546     timeout_lines = readCommand(['gtimeout', '--version'],
 547                                 exception='').splitlines()
 548 else:
 549     timeout_lines = readCommand(['timeout', '--version'],
 550                                 exception='').splitlines()
 551 # Get the first line and tokenize it
 552 timeout_version = timeout_lines[0].split() if timeout_lines else []
 553 main['TIMEOUT'] =  timeout_version and \
 554     compareVersions(timeout_version[-1], '8.13') >= 0
 555
 556 # Add a custom Check function to test for structure members.
 557 def CheckMember(context, include, decl, member, include_quotes="<>"):
 558     context.Message("Checking for member %s in %s..." %
 559                     (member, decl))
 560     text = """
 561 #include %(header)s
 562 int main(){
 563   %(decl)s test;
 564   (void)test.%(member)s;
 565   return 0;
 566 };
 567 """ % { "header" : include_quotes[0] + include + include_quotes[1],
 568         "decl" : decl,
 569         "member" : member,
 570         }
 571
 572     ret = context.TryCompile(text, extension=".cc")
 573     context.Result(ret)
 574     return ret
 575
 576 def CheckPythonLib(context):
 577     context.Message('Checking Python version... ')
 578     ret = context.TryRun(r"""
 579 #include <pybind11/embed.h>
 580
 581 int
 582 main(int argc, char **argv) {
 583     pybind11::scoped_interpreter guard{};
 584     pybind11::exec(
 585         "import sys\n"
 586         "vi = sys.version_info\n"
 587         "sys.stdout.write('%i.%i.%i' % (vi.major, vi.minor, vi.micro));\n");
 588     return 0;
 589 }
 590     """, extension=".cc")
 591     context.Result(ret[1] if ret[0] == 1 else 0)
 592     if ret[0] == 0:
 593         return None
 594     else:
 595         return tuple(map(int, ret[1].split(".")))
 596
 597 # Platform-specific configuration.  Note again that we assume that all
 598 # builds under a given build root run on the same host platform.
 599 conf = Configure(main,
 600                  conf_dir = joinpath(build_root, '.scons_config'),
 601                  log_file = joinpath(build_root, 'scons_config.log'),
 602                  custom_tests = {
 603         'CheckMember' : CheckMember,
 604         'CheckPythonLib' : CheckPythonLib,
 605         })
 606
 607 # Check if we should compile a 64 bit binary on Mac OS X/Darwin
 608 try:
 609     import platform
 610     uname = platform.uname()
 611     if uname[0] == 'Darwin' and compareVersions(uname[2], '9.0.0') >= 0:
 612         if int(readCommand('sysctl -n hw.cpu64bit_capable')[0]):
 613             main.Append(CCFLAGS=['-arch', 'x86_64'])
 614             main.Append(CFLAGS=['-arch', 'x86_64'])
 615             main.Append(LINKFLAGS=['-arch', 'x86_64'])
 616             main.Append(ASFLAGS=['-arch', 'x86_64'])
 617 except:
 618     pass
 619
 620 # Recent versions of scons substitute a "Null" object for Configure()
 621 # when configuration isn't necessary, e.g., if the "--help" option is
 622 # present.  Unfortuantely this Null object always returns false,
 623 # breaking all our configuration checks.  We replace it with our own
 624 # more optimistic null object that returns True instead.
 625 if not conf:
 626     def NullCheck(*args, **kwargs):
 627         return True
 628
 629     class NullConf:
 630         def __init__(self, env):
 631             self.env = env
 632         def Finish(self):
 633             return self.env
 634         def __getattr__(self, mname):
 635             return NullCheck
 636
 637     conf = NullConf(main)
 638
 639 # Cache build files in the supplied directory.
 640 if main['M5_BUILD_CACHE']:
 641     print('Using build cache located at', main['M5_BUILD_CACHE'])
 642     CacheDir(main['M5_BUILD_CACHE'])
 643
 644 main['USE_PYTHON'] = not GetOption('without_python')
 645 if main['USE_PYTHON']:
 646     # Find Python include and library directories for embedding the
 647     # interpreter. We rely on python-config to resolve the appropriate
 648     # includes and linker flags. ParseConfig does not seem to understand
 649     # the more exotic linker flags such as -Xlinker and -export-dynamic so
 650     # we add them explicitly below. If you want to link in an alternate
 651     # version of python, see above for instructions on how to invoke
 652     # scons with the appropriate PATH set.
 653
 654     python_config = main.Detect(main['PYTHON_CONFIG'])
 655     if python_config is None:
 656         error("Can't find a suitable python-config, tried %s" % \
 657               main['PYTHON_CONFIG'])
 658
 659     print("Info: Using Python config: %s" % (python_config, ))
 660
 661     py_includes = readCommand([python_config, '--includes'],
 662                               exception='').split()
 663     py_includes = list(filter(
 664         lambda s: match(r'.*\/include\/.*',s), py_includes))
 665     # Strip the -I from the include folders before adding them to the
 666     # CPPPATH
 667     py_includes = list(map(
 668         lambda s: s[2:] if s.startswith('-I') else s, py_includes))
 669     main.Append(CPPPATH=py_includes)
 670
 671     # Read the linker flags and split them into libraries and other link
 672     # flags. The libraries are added later through the call the CheckLib.
 673     # Note: starting in Python 3.8 the --embed flag is required to get the
 674     # -lpython3.8 linker flag
 675     retcode, cmd_stdout = readCommandWithReturn(
 676         [python_config, '--ldflags', '--embed'], exception='')
 677     if retcode != 0:
 678         # If --embed isn't detected then we're running python <3.8
 679         retcode, cmd_stdout = readCommandWithReturn(
 680             [python_config, '--ldflags'], exception='')
 681
 682     # Checking retcode again
 683     if retcode != 0:
 684         error("Failing on python-config --ldflags command")
 685
 686     py_ld_flags = cmd_stdout.split()
 687
 688     py_libs = []
 689     for lib in py_ld_flags:
 690          if not lib.startswith('-l'):
 691              main.Append(LINKFLAGS=[lib])
 692          else:
 693              lib = lib[2:]
 694              if lib not in py_libs:
 695                  py_libs.append(lib)
 696
 697     # verify that this stuff works
 698     if not conf.CheckHeader('Python.h', '<>'):
 699         error("Check failed for Python.h header in",
 700                 ' '.join(py_includes), "\n"
 701               "Two possible reasons:\n"
 702               "1. Python headers are not installed (You can install the "
 703               "package python-dev on Ubuntu and RedHat)\n"
 704               "2. SCons is using a wrong C compiler. This can happen if "
 705               "CC has the wrong value.\n"
 706               "CC = %s" % main['CC'])
 707
 708     for lib in py_libs:
 709         if not conf.CheckLib(lib):
 710             error("Can't find library %s required by python." % lib)
 711
 712 main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
 713 # Bare minimum environment that only includes python
 714 marshal_env = main.Clone()
 715 marshal_env.Append(CCFLAGS='$MARSHAL_CCFLAGS_EXTRA')
 716 marshal_env.Append(LINKFLAGS='$MARSHAL_LDFLAGS_EXTRA')
 717 py_version = conf.CheckPythonLib()
 718 if not py_version:
 719     error("Can't find a working Python installation")
 720
 721 # Found a working Python installation. Check if it meets minimum
 722 # requirements.
 723 if py_version[0] < 3 or \
 724    (py_version[0] == 3 and py_version[1] < 6):
 725     error('Python version too old. Version 3.6 or newer is required.')
 726 elif py_version[0] > 3:
 727     warning('Python version too new. Python 3 expected.')
 728
 729 # On Solaris you need to use libsocket for socket ops
 730 if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
 731    if not conf.CheckLibWithHeader('socket', 'sys/socket.h',
 732                                   'C++', 'accept(0,0,0);'):
 733        error("Can't find library with socket calls (e.g. accept()).")
 734
 735 # Check for zlib.  If the check passes, libz will be automatically
 736 # added to the LIBS environment variable.
 737 if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
 738     error('Did not find needed zlib compression library '
 739           'and/or zlib.h header file.\n'
 740           'Please install zlib and try again.')
 741
 742 # If we have the protobuf compiler, also make sure we have the
 743 # development libraries. If the check passes, libprotobuf will be
 744 # automatically added to the LIBS environment variable. After
 745 # this, we can use the HAVE_PROTOBUF flag to determine if we have
 746 # got both protoc and libprotobuf available.
 747 main['HAVE_PROTOBUF'] = main['HAVE_PROTOC'] and \
 748     conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
 749                             'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
 750
 751 # Valgrind gets much less confused if you tell it when you're using
 752 # alternative stacks.
 753 main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
 754
 755 # If we have the compiler but not the library, print another warning.
 756 if main['HAVE_PROTOC'] and not main['HAVE_PROTOBUF']:
 757     warning('Did not find protocol buffer library and/or headers.\n'
 758             'Please install libprotobuf-dev for tracing support.')
 759
 760 # Check for librt.
 761 have_posix_clock = \
 762     conf.CheckLibWithHeader(None, 'time.h', 'C',
 763                             'clock_nanosleep(0,0,NULL,NULL);') or \
 764     conf.CheckLibWithHeader('rt', 'time.h', 'C',
 765                             'clock_nanosleep(0,0,NULL,NULL);')
 766
 767 have_posix_timers = \
 768     conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
 769                             'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
 770
 771 if not GetOption('without_tcmalloc'):
 772     if conf.CheckLib('tcmalloc'):
 773         main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
 774     elif conf.CheckLib('tcmalloc_minimal'):
 775         main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
 776     else:
 777         warning("You can get a 12% performance improvement by "
 778                 "installing tcmalloc (libgoogle-perftools-dev package "
 779                 "on Ubuntu or RedHat).")
 780
 781
 782 # Detect back trace implementations. The last implementation in the
 783 # list will be used by default.
 784 backtrace_impls = [ "none" ]
 785
 786 backtrace_checker = 'char temp;' + \
 787     ' backtrace_symbols_fd((void*)&temp, 0, 0);'
 788 if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
 789     backtrace_impls.append("glibc")
 790 elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
 791                              backtrace_checker):
 792     # NetBSD and FreeBSD need libexecinfo.
 793     backtrace_impls.append("glibc")
 794     main.Append(LIBS=['execinfo'])
 795
 796 if backtrace_impls[-1] == "none":
 797     default_backtrace_impl = "none"
 798     warning("No suitable back trace implementation found.")
 799
 800 if not have_posix_clock:
 801     warning("Can't find library for POSIX clocks.")
 802
 803 # Check for <fenv.h> (C99 FP environment control)
 804 have_fenv = conf.CheckHeader('fenv.h', '<>')
 805 if not have_fenv:
 806     warning("Header file <fenv.h> not found.\n"
 807             "This host has no IEEE FP rounding mode control.")
 808
 809 # Check for <png.h> (libpng library needed if wanting to dump
 810 # frame buffer image in png format)
 811 have_png = conf.CheckHeader('png.h', '<>')
 812 if not have_png:
 813     warning("Header file <png.h> not found.\n"
 814             "This host has no libpng library.\n"
 815             "Disabling support for PNG framebuffers.")
 816
 817 # Check if we should enable KVM-based hardware virtualization. The API
 818 # we rely on exists since version 2.6.36 of the kernel, but somehow
 819 # the KVM_API_VERSION does not reflect the change. We test for one of
 820 # the types as a fall back.
 821 have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
 822 if not have_kvm:
 823     print("Info: Compatible header file <linux/kvm.h> not found, "
 824           "disabling KVM support.")
 825
 826 # Check if the TUN/TAP driver is available.
 827 have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
 828 if not have_tuntap:
 829     print("Info: Compatible header file <linux/if_tun.h> not found.")
 830
 831 # x86 needs support for xsave. We test for the structure here since we
 832 # won't be able to run new tests by the time we know which ISA we're
 833 # targeting.
 834 have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
 835                                     '#include <linux/kvm.h>') != 0
 836
 837 # Check if the requested target ISA is compatible with the host
 838 def is_isa_kvm_compatible(isa):
 839     try:
 840         import platform
 841         host_isa = platform.machine()
 842     except:
 843         warning("Failed to determine host ISA.")
 844         return False
 845
 846     if not have_posix_timers:
 847         warning("Can not enable KVM, host seems to lack support "
 848                 "for POSIX timers")
 849         return False
 850
 851     if isa == "arm":
 852         return host_isa in ( "armv7l", "aarch64" )
 853     elif isa == "x86":
 854         if host_isa != "x86_64":
 855             return False
 856
 857         if not have_kvm_xsave:
 858             warning("KVM on x86 requires xsave support in kernel headers.")
 859             return False
 860
 861         return True
 862     else:
 863         return False
 864
 865
 866 # Check if the exclude_host attribute is available. We want this to
 867 # get accurate instruction counts in KVM.
 868 main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
 869     'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
 870
 871 def check_hdf5():
 872     return \
 873         conf.CheckLibWithHeader('hdf5', 'hdf5.h', 'C',
 874                                 'H5Fcreate("", 0, 0, 0);') and \
 875         conf.CheckLibWithHeader('hdf5_cpp', 'H5Cpp.h', 'C++',
 876                                 'H5::H5File("", 0);')
 877
 878 def check_hdf5_pkg(name):
 879     print("Checking for %s using pkg-config..." % name, end="")
 880     if not have_pkg_config:
 881         print(" pkg-config not found")
 882         return False
 883
 884     try:
 885         main.ParseConfig('pkg-config --cflags-only-I --libs-only-L %s' % name)
 886         print(" yes")
 887         return True
 888     except:
 889         print(" no")
 890         return False
 891
 892 # Check if there is a pkg-config configuration for hdf5. If we find
 893 # it, setup the environment to enable linking and header inclusion. We
 894 # don't actually try to include any headers or link with hdf5 at this
 895 # stage.
 896 if not check_hdf5_pkg('hdf5-serial'):
 897     check_hdf5_pkg('hdf5')
 898
 899 # Check if the HDF5 libraries can be found. This check respects the
 900 # include path and library path provided by pkg-config. We perform
 901 # this check even if there isn't a pkg-config configuration for hdf5
 902 # since some installations don't use pkg-config.
 903 have_hdf5 = check_hdf5()
 904 if not have_hdf5:
 905     print("Warning: Couldn't find any HDF5 C++ libraries. Disabling")
 906     print("         HDF5 support.")
 907
 908 ######################################################################
 909 #
 910 # Finish the configuration
 911 #
 912 main = conf.Finish()
 913
 914 ######################################################################
 915 #
 916 # Collect all non-global variables
 917 #
 918
 919 # Define the universe of supported ISAs
 920 all_isa_list = [ ]
 921 all_gpu_isa_list = [ ]
 922 Export('all_isa_list')
 923 Export('all_gpu_isa_list')
 924
 925 class CpuModel(object):
 926     '''The CpuModel class encapsulates everything the ISA parser needs to
 927     know about a particular CPU model.'''
 928
 929     # Dict of available CPU model objects.  Accessible as CpuModel.dict.
 930     dict = {}
 931
 932     # Constructor.  Automatically adds models to CpuModel.dict.
 933     def __init__(self, name, default=False):
 934         self.name = name           # name of model
 935
 936         # This cpu is enabled by default
 937         self.default = default
 938
 939         # Add self to dict
 940         if name in CpuModel.dict:
 941             raise AttributeError("CpuModel '%s' already registered" % name)
 942         CpuModel.dict[name] = self
 943
 944 Export('CpuModel')
 945
 946 # Sticky variables get saved in the variables file so they persist from
 947 # one invocation to the next (unless overridden, in which case the new
 948 # value becomes sticky).
 949 sticky_vars = Variables(args=ARGUMENTS)
 950 Export('sticky_vars')
 951
 952 # Sticky variables that should be exported
 953 export_vars = []
 954 Export('export_vars')
 955
 956 # For Ruby
 957 all_protocols = []
 958 Export('all_protocols')
 959 protocol_dirs = []
 960 Export('protocol_dirs')
 961 slicc_includes = []
 962 Export('slicc_includes')
 963
 964 # Walk the tree and execute all SConsopts scripts that wil add to the
 965 # above variables
 966 if GetOption('verbose'):
 967     print("Reading SConsopts")
 968 for bdir in [ base_dir ] + extras_dir_list:
 969     if not isdir(bdir):
 970         error("Directory '%s' does not exist." % bdir)
 971     for root, dirs, files in os.walk(bdir):
 972         if 'SConsopts' in files:
 973             if GetOption('verbose'):
 974                 print("Reading", joinpath(root, 'SConsopts'))
 975             SConscript(joinpath(root, 'SConsopts'))
 976
 977 all_isa_list.sort()
 978 all_gpu_isa_list.sort()
 979
 980 sticky_vars.AddVariables(
 981     EnumVariable('TARGET_ISA', 'Target ISA', 'null', all_isa_list),
 982     EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'gcn3', all_gpu_isa_list),
 983     ListVariable('CPU_MODELS', 'CPU models',
 984                  sorted(n for n,m in CpuModel.dict.items() if m.default),
 985                  sorted(CpuModel.dict.keys())),
 986     BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
 987                  False),
 988     BoolVariable('USE_SSE2',
 989                  'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
 990                  False),
 991     BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
 992     BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
 993     BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
 994     BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
 995                  have_kvm),
 996     BoolVariable('USE_TUNTAP',
 997                  'Enable using a tap device to bridge to the host network',
 998                  have_tuntap),
 999     BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
1000     EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
1001                   all_protocols),
1002     EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
1003                  backtrace_impls[-1], backtrace_impls),
1004     ('NUMBER_BITS_PER_SET', 'Max elements in set (default 64)',
1005                  64),
1006     BoolVariable('USE_HDF5', 'Enable the HDF5 support', have_hdf5),
1007     )
1008
1009 # These variables get exported to #defines in config/*.hh (see src/SConscript).
1010 export_vars += ['USE_FENV', 'TARGET_ISA', 'TARGET_GPU_ISA',
1011                 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP', 'PROTOCOL',
1012                 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
1013                 'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG',
1014                 'NUMBER_BITS_PER_SET', 'USE_HDF5']
1015
1016 ###################################################
1017 #
1018 # Define a SCons builder for configuration flag headers.
1019 #
1020 ###################################################
1021
1022 # This function generates a config header file that #defines the
1023 # variable symbol to the current variable setting (0 or 1).  The source
1024 # operands are the name of the variable and a Value node containing the
1025 # value of the variable.
1026 def build_config_file(target, source, env):
1027     (variable, value) = [s.get_contents().decode('utf-8') for s in source]
1028     with open(str(target[0].abspath), 'w') as f:
1029         print('#define', variable, value, file=f)
1030     return None
1031
1032 # Combine the two functions into a scons Action object.
1033 config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1034
1035 # The emitter munges the source & target node lists to reflect what
1036 # we're really doing.
1037 def config_emitter(target, source, env):
1038     # extract variable name from Builder arg
1039     variable = str(target[0])
1040     # True target is config header file
1041     target = Dir('config').File(variable.lower() + '.hh')
1042     val = env[variable]
1043     if isinstance(val, bool):
1044         # Force value to 0/1
1045         val = int(val)
1046     elif isinstance(val, str):
1047         val = '"' + val + '"'
1048
1049     # Sources are variable name & value (packaged in SCons Value nodes)
1050     return [target], [Value(variable), Value(val)]
1051
1052 config_builder = Builder(emitter=config_emitter, action=config_action)
1053
1054 main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1055
1056 ###################################################
1057 #
1058 # Builders for static and shared partially linked object files.
1059 #
1060 ###################################################
1061
1062 partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1063                                  src_suffix='$OBJSUFFIX',
1064                                  src_builder=['StaticObject', 'Object'],
1065                                  LINKFLAGS='$PLINKFLAGS',
1066                                  LIBS='')
1067
1068 def partial_shared_emitter(target, source, env):
1069     for tgt in target:
1070         tgt.attributes.shared = 1
1071     return (target, source)
1072 partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1073                                  emitter=partial_shared_emitter,
1074                                  src_suffix='$SHOBJSUFFIX',
1075                                  src_builder='SharedObject',
1076                                  SHLINKFLAGS='$PSHLINKFLAGS',
1077                                  LIBS='')
1078
1079 main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1080                          'PartialStatic' : partial_static_builder })
1081
1082 def add_local_rpath(env, *targets):
1083     '''Set up an RPATH for a library which lives in the build directory.
1084
1085     The construction environment variable BIN_RPATH_PREFIX should be set to
1086     the relative path of the build directory starting from the location of the
1087     binary.'''
1088     for target in targets:
1089         target = env.Entry(target)
1090         if not isinstance(target, SCons.Node.FS.Dir):
1091             target = target.dir
1092         relpath = os.path.relpath(target.abspath, env['BUILDDIR'])
1093         components = [
1094             '\\$$ORIGIN',
1095             '${BIN_RPATH_PREFIX}',
1096             relpath
1097         ]
1098         env.Append(RPATH=[env.Literal(os.path.join(*components))])
1099
1100 if sys.platform != "darwin":
1101     main.Append(LINKFLAGS=Split('-z origin'))
1102
1103 main.AddMethod(add_local_rpath, 'AddLocalRPATH')
1104
1105 # builds in ext are shared across all configs in the build root.
1106 ext_dir = Dir('#ext').abspath
1107 ext_build_dirs = []
1108 for root, dirs, files in os.walk(ext_dir):
1109     if 'SConscript' in files:
1110         build_dir = os.path.relpath(root, ext_dir)
1111         ext_build_dirs.append(build_dir)
1112         main.SConscript(joinpath(root, 'SConscript'),
1113                         variant_dir=joinpath(build_root, build_dir))
1114
1115 gdb_xml_dir = joinpath(ext_dir, 'gdb-xml')
1116 Export('gdb_xml_dir')
1117
1118 ###################################################
1119 #
1120 # This builder and wrapper method are used to set up a directory with
1121 # switching headers. Those are headers which are in a generic location and
1122 # that include more specific headers from a directory chosen at build time
1123 # based on the current build settings.
1124 #
1125 ###################################################
1126
1127 def build_switching_header(target, source, env):
1128     path = str(target[0])
1129     subdir = str(source[0])
1130     dp, fp = os.path.split(path)
1131     dp = os.path.relpath(os.path.realpath(dp),
1132                          os.path.realpath(env['BUILDDIR']))
1133     with open(path, 'w') as hdr:
1134         print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1135
1136 switching_header_action = MakeAction(build_switching_header,
1137                                      Transform('GENERATE'))
1138
1139 switching_header_builder = Builder(action=switching_header_action,
1140                                    source_factory=Value,
1141                                    single_source=True)
1142
1143 main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1144
1145 def switching_headers(self, headers, source):
1146     for header in headers:
1147         self.SwitchingHeader(header, source)
1148
1149 main.AddMethod(switching_headers, 'SwitchingHeaders')
1150
1151 ###################################################
1152 #
1153 # Define build environments for selected configurations.
1154 #
1155 ###################################################
1156
1157 for variant_path in variant_paths:
1158     if not GetOption('silent'):
1159         print("Building in", variant_path)
1160
1161     # Make a copy of the build-root environment to use for this config.
1162     env = main.Clone()
1163     env['BUILDDIR'] = variant_path
1164
1165     # variant_dir is the tail component of build path, and is used to
1166     # determine the build parameters (e.g., 'X86')
1167     (build_root, variant_dir) = splitpath(variant_path)
1168
1169     # Set env variables according to the build directory config.
1170     sticky_vars.files = []
1171     # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1172     # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1173     # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1174     current_vars_file = joinpath(build_root, 'variables', variant_dir)
1175     if isfile(current_vars_file):
1176         sticky_vars.files.append(current_vars_file)
1177         if not GetOption('silent'):
1178             print("Using saved variables file %s" % current_vars_file)
1179     elif variant_dir in ext_build_dirs:
1180         # Things in ext are built without a variant directory.
1181         continue
1182     else:
1183         # Build dir-specific variables file doesn't exist.
1184
1185         # Make sure the directory is there so we can create it later
1186         opt_dir = dirname(current_vars_file)
1187         if not isdir(opt_dir):
1188             mkdir(opt_dir)
1189
1190         # Get default build variables from source tree.  Variables are
1191         # normally determined by name of $VARIANT_DIR, but can be
1192         # overridden by '--default=' arg on command line.
1193         default = GetOption('default')
1194         opts_dir = Dir('#build_opts').abspath
1195         if default:
1196             default_vars_files = [joinpath(build_root, 'variables', default),
1197                                   joinpath(opts_dir, default)]
1198         else:
1199             default_vars_files = [joinpath(opts_dir, variant_dir)]
1200         existing_files = list(filter(isfile, default_vars_files))
1201         if existing_files:
1202             default_vars_file = existing_files[0]
1203             sticky_vars.files.append(default_vars_file)
1204             print("Variables file %s not found,\n  using defaults in %s"
1205                   % (current_vars_file, default_vars_file))
1206         else:
1207             error("Cannot find variables file %s or default file(s) %s"
1208                   % (current_vars_file, ' or '.join(default_vars_files)))
1209             Exit(1)
1210
1211     # Apply current variable settings to env
1212     sticky_vars.Update(env)
1213
1214     Help('''
1215 Build variables for {dir}:
1216 {help}
1217 '''.format(dir=variant_dir, help=sticky_vars.GenerateHelpText(env)),
1218          append=True)
1219
1220     # Process variable settings.
1221
1222     if not have_fenv and env['USE_FENV']:
1223         warning("<fenv.h> not available; forcing USE_FENV to False in",
1224                 variant_dir + ".")
1225         env['USE_FENV'] = False
1226
1227     if not env['USE_FENV']:
1228         warning("No IEEE FP rounding mode control in", variant_dir + ".\n"
1229                 "FP results may deviate slightly from other platforms.")
1230
1231     if not have_png and env['USE_PNG']:
1232         warning("<png.h> not available; forcing USE_PNG to False in",
1233                 variant_dir + ".")
1234         env['USE_PNG'] = False
1235
1236     if env['USE_PNG']:
1237         env.Append(LIBS=['png'])
1238
1239     if env['EFENCE']:
1240         env.Append(LIBS=['efence'])
1241
1242     if env['USE_KVM']:
1243         if not have_kvm:
1244             warning("Can not enable KVM, host seems to lack KVM support")
1245             env['USE_KVM'] = False
1246         elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1247             print("Info: KVM support disabled due to unsupported host and "
1248                   "target ISA combination")
1249             env['USE_KVM'] = False
1250
1251     if env['USE_TUNTAP']:
1252         if not have_tuntap:
1253             warning("Can't connect EtherTap with a tap device.")
1254             env['USE_TUNTAP'] = False
1255
1256     if env['BUILD_GPU']:
1257         env.Append(CPPDEFINES=['BUILD_GPU'])
1258
1259     # Warn about missing optional functionality
1260     if env['USE_KVM']:
1261         if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1262             warning("perf_event headers lack support for the exclude_host "
1263                     "attribute. KVM instruction counts will be inaccurate.")
1264
1265     # Save sticky variable settings back to current variables file
1266     sticky_vars.Save(current_vars_file, env)
1267
1268     if env['USE_SSE2']:
1269         env.Append(CCFLAGS=['-msse2'])
1270
1271     env.Append(CCFLAGS='$CCFLAGS_EXTRA')
1272     env.Append(LINKFLAGS='$LDFLAGS_EXTRA')
1273
1274     # The src/SConscript file sets up the build rules in 'env' according
1275     # to the configured variables.  It returns a list of environments,
1276     # one for each variant build (debug, opt, etc.)
1277     SConscript('src/SConscript', variant_dir=variant_path,
1278                exports=['env', 'marshal_env'])
1279
1280 atexit.register(summarize_warnings)