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