SConstruct revision 12688:8d2a4af53baa
1# -*- mode:python -*-
2
3# Copyright (c) 2013, 2015-2017 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# Authors: Steve Reinhardt
44#          Nathan Binkert
45
46###################################################
47#
48# SCons top-level build description (SConstruct) file.
49#
50# While in this directory ('gem5'), just type 'scons' to build the default
51# configuration (see below), or type 'scons build/<CONFIG>/<binary>'
52# to build some other configuration (e.g., 'build/ALPHA/gem5.opt' for
53# the optimized full-system version).
54#
55# You can build gem5 in a different directory as long as there is a
56# 'build/<CONFIG>' somewhere along the target path.  The build system
57# expects that all configs under the same build directory are being
58# built for the same host system.
59#
60# Examples:
61#
62#   The following two commands are equivalent.  The '-u' option tells
63#   scons to search up the directory tree for this SConstruct file.
64#   % cd <path-to-src>/gem5 ; scons build/ALPHA/gem5.debug
65#   % cd <path-to-src>/gem5/build/ALPHA; scons -u gem5.debug
66#
67#   The following two commands are equivalent and demonstrate building
68#   in a directory outside of the source tree.  The '-C' option tells
69#   scons to chdir to the specified directory to find this SConstruct
70#   file.
71#   % cd <path-to-src>/gem5 ; scons /local/foo/build/ALPHA/gem5.debug
72#   % cd /local/foo/build/ALPHA; scons -C <path-to-src>/gem5 gem5.debug
73#
74# You can use 'scons -H' to print scons options.  If you're in this
75# 'gem5' directory (or use -u or -C to tell scons where to find this
76# file), you can use 'scons -h' to print all the gem5-specific build
77# options as well.
78#
79###################################################
80
81from __future__ import print_function
82
83# Global Python includes
84import itertools
85import os
86import re
87import shutil
88import subprocess
89import sys
90
91from os import mkdir, environ
92from os.path import abspath, basename, dirname, expanduser, normpath
93from os.path import exists,  isdir, isfile
94from os.path import join as joinpath, split as splitpath
95
96# SCons includes
97import SCons
98import SCons.Node
99
100from m5.util import compareVersions, readCommand
101
102help_texts = {
103    "options" : "",
104    "global_vars" : "",
105    "local_vars" : ""
106}
107
108Export("help_texts")
109
110
111# There's a bug in scons in that (1) by default, the help texts from
112# AddOption() are supposed to be displayed when you type 'scons -h'
113# and (2) you can override the help displayed by 'scons -h' using the
114# Help() function, but these two features are incompatible: once
115# you've overridden the help text using Help(), there's no way to get
116# at the help texts from AddOptions.  See:
117#     http://scons.tigris.org/issues/show_bug.cgi?id=2356
118#     http://scons.tigris.org/issues/show_bug.cgi?id=2611
119# This hack lets us extract the help text from AddOptions and
120# re-inject it via Help().  Ideally someday this bug will be fixed and
121# we can just use AddOption directly.
122def AddLocalOption(*args, **kwargs):
123    col_width = 30
124
125    help = "  " + ", ".join(args)
126    if "help" in kwargs:
127        length = len(help)
128        if length >= col_width:
129            help += "\n" + " " * col_width
130        else:
131            help += " " * (col_width - length)
132        help += kwargs["help"]
133    help_texts["options"] += help + "\n"
134
135    AddOption(*args, **kwargs)
136
137AddLocalOption('--colors', dest='use_colors', action='store_true',
138               help="Add color to abbreviated scons output")
139AddLocalOption('--no-colors', dest='use_colors', action='store_false',
140               help="Don't add color to abbreviated scons output")
141AddLocalOption('--with-cxx-config', dest='with_cxx_config',
142               action='store_true',
143               help="Build with support for C++-based configuration")
144AddLocalOption('--default', dest='default', type='string', action='store',
145               help='Override which build_opts file to use for defaults')
146AddLocalOption('--ignore-style', dest='ignore_style', action='store_true',
147               help='Disable style checking hooks')
148AddLocalOption('--no-lto', dest='no_lto', action='store_true',
149               help='Disable Link-Time Optimization for fast')
150AddLocalOption('--force-lto', dest='force_lto', action='store_true',
151               help='Use Link-Time Optimization instead of partial linking' +
152                    ' when the compiler doesn\'t support using them together.')
153AddLocalOption('--update-ref', dest='update_ref', action='store_true',
154               help='Update test reference outputs')
155AddLocalOption('--verbose', dest='verbose', action='store_true',
156               help='Print full tool command lines')
157AddLocalOption('--without-python', dest='without_python',
158               action='store_true',
159               help='Build without Python configuration support')
160AddLocalOption('--without-tcmalloc', dest='without_tcmalloc',
161               action='store_true',
162               help='Disable linking against tcmalloc')
163AddLocalOption('--with-ubsan', dest='with_ubsan', action='store_true',
164               help='Build with Undefined Behavior Sanitizer if available')
165AddLocalOption('--with-asan', dest='with_asan', action='store_true',
166               help='Build with Address Sanitizer if available')
167
168if GetOption('no_lto') and GetOption('force_lto'):
169    print('--no-lto and --force-lto are mutually exclusive')
170    Exit(1)
171
172########################################################################
173#
174# Set up the main build environment.
175#
176########################################################################
177
178main = Environment()
179
180from gem5_scons import Transform
181from gem5_scons.util import get_termcap
182termcap = get_termcap()
183
184main_dict_keys = main.Dictionary().keys()
185
186# Check that we have a C/C++ compiler
187if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
188    print("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
189    Exit(1)
190
191###################################################
192#
193# Figure out which configurations to set up based on the path(s) of
194# the target(s).
195#
196###################################################
197
198# Find default configuration & binary.
199Default(environ.get('M5_DEFAULT_BINARY', 'build/ALPHA/gem5.debug'))
200
201# helper function: find last occurrence of element in list
202def rfind(l, elt, offs = -1):
203    for i in range(len(l)+offs, 0, -1):
204        if l[i] == elt:
205            return i
206    raise ValueError, "element not found"
207
208# Take a list of paths (or SCons Nodes) and return a list with all
209# paths made absolute and ~-expanded.  Paths will be interpreted
210# relative to the launch directory unless a different root is provided
211def makePathListAbsolute(path_list, root=GetLaunchDir()):
212    return [abspath(joinpath(root, expanduser(str(p))))
213            for p in path_list]
214
215# Each target must have 'build' in the interior of the path; the
216# directory below this will determine the build parameters.  For
217# example, for target 'foo/bar/build/ALPHA_SE/arch/alpha/blah.do' we
218# recognize that ALPHA_SE specifies the configuration because it
219# follow 'build' in the build path.
220
221# The funky assignment to "[:]" is needed to replace the list contents
222# in place rather than reassign the symbol to a new list, which
223# doesn't work (obviously!).
224BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
225
226# Generate a list of the unique build roots and configs that the
227# collected targets reference.
228variant_paths = []
229build_root = None
230for t in BUILD_TARGETS:
231    path_dirs = t.split('/')
232    try:
233        build_top = rfind(path_dirs, 'build', -2)
234    except:
235        print("Error: no non-leaf 'build' dir found on target path", t)
236        Exit(1)
237    this_build_root = joinpath('/',*path_dirs[:build_top+1])
238    if not build_root:
239        build_root = this_build_root
240    else:
241        if this_build_root != build_root:
242            print("Error: build targets not under same build root\n"
243                  "  %s\n  %s" % (build_root, this_build_root))
244            Exit(1)
245    variant_path = joinpath('/',*path_dirs[:build_top+2])
246    if variant_path not in variant_paths:
247        variant_paths.append(variant_path)
248
249# Make sure build_root exists (might not if this is the first build there)
250if not isdir(build_root):
251    mkdir(build_root)
252main['BUILDROOT'] = build_root
253
254Export('main')
255
256main.SConsignFile(joinpath(build_root, "sconsign"))
257
258# Default duplicate option is to use hard links, but this messes up
259# when you use emacs to edit a file in the target dir, as emacs moves
260# file to file~ then copies to file, breaking the link.  Symbolic
261# (soft) links work better.
262main.SetOption('duplicate', 'soft-copy')
263
264#
265# Set up global sticky variables... these are common to an entire build
266# tree (not specific to a particular build like ALPHA_SE)
267#
268
269global_vars_file = joinpath(build_root, 'variables.global')
270
271global_vars = Variables(global_vars_file, args=ARGUMENTS)
272
273global_vars.AddVariables(
274    ('CC', 'C compiler', environ.get('CC', main['CC'])),
275    ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
276    ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
277    ('BATCH', 'Use batch pool for build and tests', False),
278    ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
279    ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
280    ('EXTRAS', 'Add extra directories to the compilation', '')
281    )
282
283# Update main environment with values from ARGUMENTS & global_vars_file
284global_vars.Update(main)
285help_texts["global_vars"] += global_vars.GenerateHelpText(main)
286
287# Save sticky variable settings back to current variables file
288global_vars.Save(global_vars_file, main)
289
290# Parse EXTRAS variable to build list of all directories where we're
291# look for sources etc.  This list is exported as extras_dir_list.
292base_dir = main.srcdir.abspath
293if main['EXTRAS']:
294    extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
295else:
296    extras_dir_list = []
297
298Export('base_dir')
299Export('extras_dir_list')
300
301# the ext directory should be on the #includes path
302main.Append(CPPPATH=[Dir('ext')])
303
304# Add shared top-level headers
305main.Prepend(CPPPATH=Dir('include'))
306
307if GetOption('verbose'):
308    def MakeAction(action, string, *args, **kwargs):
309        return Action(action, *args, **kwargs)
310else:
311    MakeAction = Action
312    main['CCCOMSTR']        = Transform("CC")
313    main['CXXCOMSTR']       = Transform("CXX")
314    main['ASCOMSTR']        = Transform("AS")
315    main['ARCOMSTR']        = Transform("AR", 0)
316    main['LINKCOMSTR']      = Transform("LINK", 0)
317    main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
318    main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
319    main['M4COMSTR']        = Transform("M4")
320    main['SHCCCOMSTR']      = Transform("SHCC")
321    main['SHCXXCOMSTR']     = Transform("SHCXX")
322Export('MakeAction')
323
324# Initialize the Link-Time Optimization (LTO) flags
325main['LTO_CCFLAGS'] = []
326main['LTO_LDFLAGS'] = []
327
328# According to the readme, tcmalloc works best if the compiler doesn't
329# assume that we're using the builtin malloc and friends. These flags
330# are compiler-specific, so we need to set them after we detect which
331# compiler we're using.
332main['TCMALLOC_CCFLAGS'] = []
333
334CXX_version = readCommand([main['CXX'],'--version'], exception=False)
335CXX_V = readCommand([main['CXX'],'-V'], exception=False)
336
337main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
338main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
339if main['GCC'] + main['CLANG'] > 1:
340    print('Error: How can we have two at the same time?')
341    Exit(1)
342
343# Set up default C++ compiler flags
344if main['GCC'] or main['CLANG']:
345    # As gcc and clang share many flags, do the common parts here
346    main.Append(CCFLAGS=['-pipe'])
347    main.Append(CCFLAGS=['-fno-strict-aliasing'])
348    # Enable -Wall and -Wextra and then disable the few warnings that
349    # we consistently violate
350    main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
351                         '-Wno-sign-compare', '-Wno-unused-parameter'])
352    # We always compile using C++11
353    main.Append(CXXFLAGS=['-std=c++11'])
354    if sys.platform.startswith('freebsd'):
355        main.Append(CCFLAGS=['-I/usr/local/include'])
356        main.Append(CXXFLAGS=['-I/usr/local/include'])
357
358    main['FILTER_PSHLINKFLAGS'] = lambda x: str(x).replace(' -shared', '')
359    main['PSHLINKFLAGS'] = main.subst('${FILTER_PSHLINKFLAGS(SHLINKFLAGS)}')
360    main['PLINKFLAGS'] = main.subst('${LINKFLAGS}')
361    shared_partial_flags = ['-r', '-nostdlib']
362    main.Append(PSHLINKFLAGS=shared_partial_flags)
363    main.Append(PLINKFLAGS=shared_partial_flags)
364
365    # Treat warnings as errors but white list some warnings that we
366    # want to allow (e.g., deprecation warnings).
367    main.Append(CCFLAGS=['-Werror',
368                         '-Wno-error=deprecated-declarations',
369                         '-Wno-error=deprecated',
370                        ])
371else:
372    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
373    print("Don't know what compiler options to use for your compiler.")
374    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
375    print(termcap.Yellow + '       version:' + termcap.Normal, end = ' ')
376    if not CXX_version:
377        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
378              termcap.Normal)
379    else:
380        print(CXX_version.replace('\n', '<nl>'))
381    print("       If you're trying to use a compiler other than GCC")
382    print("       or clang, there appears to be something wrong with your")
383    print("       environment.")
384    print("       ")
385    print("       If you are trying to use a compiler other than those listed")
386    print("       above you will need to ease fix SConstruct and ")
387    print("       src/SConscript to support that compiler.")
388    Exit(1)
389
390if main['GCC']:
391    # Check for a supported version of gcc. >= 4.8 is chosen for its
392    # level of c++11 support. See
393    # http://gcc.gnu.org/projects/cxx0x.html for details.
394    gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
395    if compareVersions(gcc_version, "4.8") < 0:
396        print('Error: gcc version 4.8 or newer required.')
397        print('       Installed version: ', gcc_version)
398        Exit(1)
399
400    main['GCC_VERSION'] = gcc_version
401
402    if compareVersions(gcc_version, '4.9') >= 0:
403        # Incremental linking with LTO is currently broken in gcc versions
404        # 4.9 and above. A version where everything works completely hasn't
405        # yet been identified.
406        #
407        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548
408        main['BROKEN_INCREMENTAL_LTO'] = True
409    if compareVersions(gcc_version, '6.0') >= 0:
410        # gcc versions 6.0 and greater accept an -flinker-output flag which
411        # selects what type of output the linker should generate. This is
412        # necessary for incremental lto to work, but is also broken in
413        # current versions of gcc. It may not be necessary in future
414        # versions. We add it here since it might be, and as a reminder that
415        # it exists. It's excluded if lto is being forced.
416        #
417        # https://gcc.gnu.org/gcc-6/changes.html
418        # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html
419        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866
420        if not GetOption('force_lto'):
421            main.Append(PSHLINKFLAGS='-flinker-output=rel')
422            main.Append(PLINKFLAGS='-flinker-output=rel')
423
424    # gcc from version 4.8 and above generates "rep; ret" instructions
425    # to avoid performance penalties on certain AMD chips. Older
426    # assemblers detect this as an error, "Error: expecting string
427    # instruction after `rep'"
428    as_version_raw = readCommand([main['AS'], '-v', '/dev/null',
429                                  '-o', '/dev/null'],
430                                 exception=False).split()
431
432    # version strings may contain extra distro-specific
433    # qualifiers, so play it safe and keep only what comes before
434    # the first hyphen
435    as_version = as_version_raw[-1].split('-')[0] if as_version_raw else None
436
437    if not as_version or compareVersions(as_version, "2.23") < 0:
438        print(termcap.Yellow + termcap.Bold +
439            'Warning: This combination of gcc and binutils have' +
440            ' known incompatibilities.\n' +
441            '         If you encounter build problems, please update ' +
442            'binutils to 2.23.' +
443            termcap.Normal)
444
445    # Make sure we warn if the user has requested to compile with the
446    # Undefined Benahvior Sanitizer and this version of gcc does not
447    # support it.
448    if GetOption('with_ubsan') and \
449            compareVersions(gcc_version, '4.9') < 0:
450        print(termcap.Yellow + termcap.Bold +
451            'Warning: UBSan is only supported using gcc 4.9 and later.' +
452            termcap.Normal)
453
454    disable_lto = GetOption('no_lto')
455    if not disable_lto and main.get('BROKEN_INCREMENTAL_LTO', False) and \
456            not GetOption('force_lto'):
457        print(termcap.Yellow + termcap.Bold +
458            'Warning: Your compiler doesn\'t support incremental linking' +
459            ' and lto at the same time, so lto is being disabled. To force' +
460            ' lto on anyway, use the --force-lto option. That will disable' +
461            ' partial linking.' +
462            termcap.Normal)
463        disable_lto = True
464
465    # Add the appropriate Link-Time Optimization (LTO) flags
466    # unless LTO is explicitly turned off. Note that these flags
467    # are only used by the fast target.
468    if not disable_lto:
469        # Pass the LTO flag when compiling to produce GIMPLE
470        # output, we merely create the flags here and only append
471        # them later
472        main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
473
474        # Use the same amount of jobs for LTO as we are running
475        # scons with
476        main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
477
478    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
479                                  '-fno-builtin-realloc', '-fno-builtin-free'])
480
481    # The address sanitizer is available for gcc >= 4.8
482    if GetOption('with_asan'):
483        if GetOption('with_ubsan') and \
484                compareVersions(main['GCC_VERSION'], '4.9') >= 0:
485            main.Append(CCFLAGS=['-fsanitize=address,undefined',
486                                 '-fno-omit-frame-pointer'],
487                       LINKFLAGS='-fsanitize=address,undefined')
488        else:
489            main.Append(CCFLAGS=['-fsanitize=address',
490                                 '-fno-omit-frame-pointer'],
491                       LINKFLAGS='-fsanitize=address')
492    # Only gcc >= 4.9 supports UBSan, so check both the version
493    # and the command-line option before adding the compiler and
494    # linker flags.
495    elif GetOption('with_ubsan') and \
496            compareVersions(main['GCC_VERSION'], '4.9') >= 0:
497        main.Append(CCFLAGS='-fsanitize=undefined')
498        main.Append(LINKFLAGS='-fsanitize=undefined')
499
500elif main['CLANG']:
501    # Check for a supported version of clang, >= 3.1 is needed to
502    # support similar features as gcc 4.8. See
503    # http://clang.llvm.org/cxx_status.html for details
504    clang_version_re = re.compile(".* version (\d+\.\d+)")
505    clang_version_match = clang_version_re.search(CXX_version)
506    if (clang_version_match):
507        clang_version = clang_version_match.groups()[0]
508        if compareVersions(clang_version, "3.1") < 0:
509            print('Error: clang version 3.1 or newer required.')
510            print('       Installed version:', clang_version)
511            Exit(1)
512    else:
513        print('Error: Unable to determine clang version.')
514        Exit(1)
515
516    # clang has a few additional warnings that we disable, extraneous
517    # parantheses are allowed due to Ruby's printing of the AST,
518    # finally self assignments are allowed as the generated CPU code
519    # is relying on this
520    main.Append(CCFLAGS=['-Wno-parentheses',
521                         '-Wno-self-assign',
522                         # Some versions of libstdc++ (4.8?) seem to
523                         # use struct hash and class hash
524                         # interchangeably.
525                         '-Wno-mismatched-tags',
526                         ])
527
528    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin'])
529
530    # On Mac OS X/Darwin we need to also use libc++ (part of XCode) as
531    # opposed to libstdc++, as the later is dated.
532    if sys.platform == "darwin":
533        main.Append(CXXFLAGS=['-stdlib=libc++'])
534        main.Append(LIBS=['c++'])
535
536    # On FreeBSD we need libthr.
537    if sys.platform.startswith('freebsd'):
538        main.Append(LIBS=['thr'])
539
540    # We require clang >= 3.1, so there is no need to check any
541    # versions here.
542    if GetOption('with_ubsan'):
543        if GetOption('with_asan'):
544            env.Append(CCFLAGS=['-fsanitize=address,undefined',
545                                '-fno-omit-frame-pointer'],
546                       LINKFLAGS='-fsanitize=address,undefined')
547        else:
548            env.Append(CCFLAGS='-fsanitize=undefined',
549                       LINKFLAGS='-fsanitize=undefined')
550
551    elif GetOption('with_asan'):
552        env.Append(CCFLAGS=['-fsanitize=address',
553                            '-fno-omit-frame-pointer'],
554                   LINKFLAGS='-fsanitize=address')
555
556else:
557    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
558    print("Don't know what compiler options to use for your compiler.")
559    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
560    print(termcap.Yellow + '       version:' + termcap.Normal, end=' ')
561    if not CXX_version:
562        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
563              termcap.Normal)
564    else:
565        print(CXX_version.replace('\n', '<nl>'))
566    print("       If you're trying to use a compiler other than GCC")
567    print("       or clang, there appears to be something wrong with your")
568    print("       environment.")
569    print("       ")
570    print("       If you are trying to use a compiler other than those listed")
571    print("       above you will need to ease fix SConstruct and ")
572    print("       src/SConscript to support that compiler.")
573    Exit(1)
574
575# Set up common yacc/bison flags (needed for Ruby)
576main['YACCFLAGS'] = '-d'
577main['YACCHXXFILESUFFIX'] = '.hh'
578
579# Do this after we save setting back, or else we'll tack on an
580# extra 'qdo' every time we run scons.
581if main['BATCH']:
582    main['CC']     = main['BATCH_CMD'] + ' ' + main['CC']
583    main['CXX']    = main['BATCH_CMD'] + ' ' + main['CXX']
584    main['AS']     = main['BATCH_CMD'] + ' ' + main['AS']
585    main['AR']     = main['BATCH_CMD'] + ' ' + main['AR']
586    main['RANLIB'] = main['BATCH_CMD'] + ' ' + main['RANLIB']
587
588if sys.platform == 'cygwin':
589    # cygwin has some header file issues...
590    main.Append(CCFLAGS=["-Wno-uninitialized"])
591
592# Check for the protobuf compiler
593protoc_version = readCommand([main['PROTOC'], '--version'],
594                             exception='').split()
595
596# First two words should be "libprotoc x.y.z"
597if len(protoc_version) < 2 or protoc_version[0] != 'libprotoc':
598    print(termcap.Yellow + termcap.Bold +
599        'Warning: Protocol buffer compiler (protoc) not found.\n' +
600        '         Please install protobuf-compiler for tracing support.' +
601        termcap.Normal)
602    main['PROTOC'] = False
603else:
604    # Based on the availability of the compress stream wrappers,
605    # require 2.1.0
606    min_protoc_version = '2.1.0'
607    if compareVersions(protoc_version[1], min_protoc_version) < 0:
608        print(termcap.Yellow + termcap.Bold +
609            'Warning: protoc version', min_protoc_version,
610            'or newer required.\n' +
611            '         Installed version:', protoc_version[1],
612            termcap.Normal)
613        main['PROTOC'] = False
614    else:
615        # Attempt to determine the appropriate include path and
616        # library path using pkg-config, that means we also need to
617        # check for pkg-config. Note that it is possible to use
618        # protobuf without the involvement of pkg-config. Later on we
619        # check go a library config check and at that point the test
620        # will fail if libprotobuf cannot be found.
621        if readCommand(['pkg-config', '--version'], exception=''):
622            try:
623                # Attempt to establish what linking flags to add for protobuf
624                # using pkg-config
625                main.ParseConfig('pkg-config --cflags --libs-only-L protobuf')
626            except:
627                print(termcap.Yellow + termcap.Bold +
628                    'Warning: pkg-config could not get protobuf flags.' +
629                    termcap.Normal)
630
631
632# Check for 'timeout' from GNU coreutils. If present, regressions will
633# be run with a time limit. We require version 8.13 since we rely on
634# support for the '--foreground' option.
635if sys.platform.startswith('freebsd'):
636    timeout_lines = readCommand(['gtimeout', '--version'],
637                                exception='').splitlines()
638else:
639    timeout_lines = readCommand(['timeout', '--version'],
640                                exception='').splitlines()
641# Get the first line and tokenize it
642timeout_version = timeout_lines[0].split() if timeout_lines else []
643main['TIMEOUT'] =  timeout_version and \
644    compareVersions(timeout_version[-1], '8.13') >= 0
645
646# Add a custom Check function to test for structure members.
647def CheckMember(context, include, decl, member, include_quotes="<>"):
648    context.Message("Checking for member %s in %s..." %
649                    (member, decl))
650    text = """
651#include %(header)s
652int main(){
653  %(decl)s test;
654  (void)test.%(member)s;
655  return 0;
656};
657""" % { "header" : include_quotes[0] + include + include_quotes[1],
658        "decl" : decl,
659        "member" : member,
660        }
661
662    ret = context.TryCompile(text, extension=".cc")
663    context.Result(ret)
664    return ret
665
666# Platform-specific configuration.  Note again that we assume that all
667# builds under a given build root run on the same host platform.
668conf = Configure(main,
669                 conf_dir = joinpath(build_root, '.scons_config'),
670                 log_file = joinpath(build_root, 'scons_config.log'),
671                 custom_tests = {
672        'CheckMember' : CheckMember,
673        })
674
675# Check if we should compile a 64 bit binary on Mac OS X/Darwin
676try:
677    import platform
678    uname = platform.uname()
679    if uname[0] == 'Darwin' and compareVersions(uname[2], '9.0.0') >= 0:
680        if int(readCommand('sysctl -n hw.cpu64bit_capable')[0]):
681            main.Append(CCFLAGS=['-arch', 'x86_64'])
682            main.Append(CFLAGS=['-arch', 'x86_64'])
683            main.Append(LINKFLAGS=['-arch', 'x86_64'])
684            main.Append(ASFLAGS=['-arch', 'x86_64'])
685except:
686    pass
687
688# Recent versions of scons substitute a "Null" object for Configure()
689# when configuration isn't necessary, e.g., if the "--help" option is
690# present.  Unfortuantely this Null object always returns false,
691# breaking all our configuration checks.  We replace it with our own
692# more optimistic null object that returns True instead.
693if not conf:
694    def NullCheck(*args, **kwargs):
695        return True
696
697    class NullConf:
698        def __init__(self, env):
699            self.env = env
700        def Finish(self):
701            return self.env
702        def __getattr__(self, mname):
703            return NullCheck
704
705    conf = NullConf(main)
706
707# Cache build files in the supplied directory.
708if main['M5_BUILD_CACHE']:
709    print('Using build cache located at', main['M5_BUILD_CACHE'])
710    CacheDir(main['M5_BUILD_CACHE'])
711
712main['USE_PYTHON'] = not GetOption('without_python')
713if main['USE_PYTHON']:
714    # Find Python include and library directories for embedding the
715    # interpreter. We rely on python-config to resolve the appropriate
716    # includes and linker flags. ParseConfig does not seem to understand
717    # the more exotic linker flags such as -Xlinker and -export-dynamic so
718    # we add them explicitly below. If you want to link in an alternate
719    # version of python, see above for instructions on how to invoke
720    # scons with the appropriate PATH set.
721    #
722    # First we check if python2-config exists, else we use python-config
723    python_config = readCommand(['which', 'python2-config'],
724                                exception='').strip()
725    if not os.path.exists(python_config):
726        python_config = readCommand(['which', 'python-config'],
727                                    exception='').strip()
728    py_includes = readCommand([python_config, '--includes'],
729                              exception='').split()
730    # Strip the -I from the include folders before adding them to the
731    # CPPPATH
732    main.Append(CPPPATH=map(lambda inc: inc[2:], py_includes))
733
734    # Read the linker flags and split them into libraries and other link
735    # flags. The libraries are added later through the call the CheckLib.
736    py_ld_flags = readCommand([python_config, '--ldflags'],
737        exception='').split()
738    py_libs = []
739    for lib in py_ld_flags:
740         if not lib.startswith('-l'):
741             main.Append(LINKFLAGS=[lib])
742         else:
743             lib = lib[2:]
744             if lib not in py_libs:
745                 py_libs.append(lib)
746
747    # verify that this stuff works
748    if not conf.CheckHeader('Python.h', '<>'):
749        print("Error: can't find Python.h header in", py_includes)
750        print("Install Python headers (package python-dev on " +
751              "Ubuntu and RedHat)")
752        Exit(1)
753
754    for lib in py_libs:
755        if not conf.CheckLib(lib):
756            print("Error: can't find library %s required by python" % lib)
757            Exit(1)
758
759# On Solaris you need to use libsocket for socket ops
760if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
761   if not conf.CheckLibWithHeader('socket', 'sys/socket.h', 'C++', 'accept(0,0,0);'):
762       print("Can't find library with socket calls (e.g. accept())")
763       Exit(1)
764
765# Check for zlib.  If the check passes, libz will be automatically
766# added to the LIBS environment variable.
767if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
768    print('Error: did not find needed zlib compression library '
769          'and/or zlib.h header file.')
770    print('       Please install zlib and try again.')
771    Exit(1)
772
773# If we have the protobuf compiler, also make sure we have the
774# development libraries. If the check passes, libprotobuf will be
775# automatically added to the LIBS environment variable. After
776# this, we can use the HAVE_PROTOBUF flag to determine if we have
777# got both protoc and libprotobuf available.
778main['HAVE_PROTOBUF'] = main['PROTOC'] and \
779    conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
780                            'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
781
782# If we have the compiler but not the library, print another warning.
783if main['PROTOC'] and not main['HAVE_PROTOBUF']:
784    print(termcap.Yellow + termcap.Bold +
785        'Warning: did not find protocol buffer library and/or headers.\n' +
786    '       Please install libprotobuf-dev for tracing support.' +
787    termcap.Normal)
788
789# Check for librt.
790have_posix_clock = \
791    conf.CheckLibWithHeader(None, 'time.h', 'C',
792                            'clock_nanosleep(0,0,NULL,NULL);') or \
793    conf.CheckLibWithHeader('rt', 'time.h', 'C',
794                            'clock_nanosleep(0,0,NULL,NULL);')
795
796have_posix_timers = \
797    conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
798                            'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
799
800if not GetOption('without_tcmalloc'):
801    if conf.CheckLib('tcmalloc'):
802        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
803    elif conf.CheckLib('tcmalloc_minimal'):
804        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
805    else:
806        print(termcap.Yellow + termcap.Bold +
807              "You can get a 12% performance improvement by "
808              "installing tcmalloc (libgoogle-perftools-dev package "
809              "on Ubuntu or RedHat)." + termcap.Normal)
810
811
812# Detect back trace implementations. The last implementation in the
813# list will be used by default.
814backtrace_impls = [ "none" ]
815
816backtrace_checker = 'char temp;' + \
817    ' backtrace_symbols_fd((void*)&temp, 0, 0);'
818if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
819    backtrace_impls.append("glibc")
820elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
821                             backtrace_checker):
822    # NetBSD and FreeBSD need libexecinfo.
823    backtrace_impls.append("glibc")
824    main.Append(LIBS=['execinfo'])
825
826if backtrace_impls[-1] == "none":
827    default_backtrace_impl = "none"
828    print(termcap.Yellow + termcap.Bold +
829        "No suitable back trace implementation found." +
830        termcap.Normal)
831
832if not have_posix_clock:
833    print("Can't find library for POSIX clocks.")
834
835# Check for <fenv.h> (C99 FP environment control)
836have_fenv = conf.CheckHeader('fenv.h', '<>')
837if not have_fenv:
838    print("Warning: Header file <fenv.h> not found.")
839    print("         This host has no IEEE FP rounding mode control.")
840
841# Check for <png.h> (libpng library needed if wanting to dump
842# frame buffer image in png format)
843have_png = conf.CheckHeader('png.h', '<>')
844if not have_png:
845    print("Warning: Header file <png.h> not found.")
846    print("         This host has no libpng library.")
847    print("         Disabling support for PNG framebuffers.")
848
849# Check if we should enable KVM-based hardware virtualization. The API
850# we rely on exists since version 2.6.36 of the kernel, but somehow
851# the KVM_API_VERSION does not reflect the change. We test for one of
852# the types as a fall back.
853have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
854if not have_kvm:
855    print("Info: Compatible header file <linux/kvm.h> not found, "
856          "disabling KVM support.")
857
858# Check if the TUN/TAP driver is available.
859have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
860if not have_tuntap:
861    print("Info: Compatible header file <linux/if_tun.h> not found.")
862
863# x86 needs support for xsave. We test for the structure here since we
864# won't be able to run new tests by the time we know which ISA we're
865# targeting.
866have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
867                                    '#include <linux/kvm.h>') != 0
868
869# Check if the requested target ISA is compatible with the host
870def is_isa_kvm_compatible(isa):
871    try:
872        import platform
873        host_isa = platform.machine()
874    except:
875        print("Warning: Failed to determine host ISA.")
876        return False
877
878    if not have_posix_timers:
879        print("Warning: Can not enable KVM, host seems to lack support "
880              "for POSIX timers")
881        return False
882
883    if isa == "arm":
884        return host_isa in ( "armv7l", "aarch64" )
885    elif isa == "x86":
886        if host_isa != "x86_64":
887            return False
888
889        if not have_kvm_xsave:
890            print("KVM on x86 requires xsave support in kernel headers.")
891            return False
892
893        return True
894    else:
895        return False
896
897
898# Check if the exclude_host attribute is available. We want this to
899# get accurate instruction counts in KVM.
900main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
901    'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
902
903
904######################################################################
905#
906# Finish the configuration
907#
908main = conf.Finish()
909
910######################################################################
911#
912# Collect all non-global variables
913#
914
915# Define the universe of supported ISAs
916all_isa_list = [ ]
917all_gpu_isa_list = [ ]
918Export('all_isa_list')
919Export('all_gpu_isa_list')
920
921class CpuModel(object):
922    '''The CpuModel class encapsulates everything the ISA parser needs to
923    know about a particular CPU model.'''
924
925    # Dict of available CPU model objects.  Accessible as CpuModel.dict.
926    dict = {}
927
928    # Constructor.  Automatically adds models to CpuModel.dict.
929    def __init__(self, name, default=False):
930        self.name = name           # name of model
931
932        # This cpu is enabled by default
933        self.default = default
934
935        # Add self to dict
936        if name in CpuModel.dict:
937            raise AttributeError, "CpuModel '%s' already registered" % name
938        CpuModel.dict[name] = self
939
940Export('CpuModel')
941
942# Sticky variables get saved in the variables file so they persist from
943# one invocation to the next (unless overridden, in which case the new
944# value becomes sticky).
945sticky_vars = Variables(args=ARGUMENTS)
946Export('sticky_vars')
947
948# Sticky variables that should be exported
949export_vars = []
950Export('export_vars')
951
952# For Ruby
953all_protocols = []
954Export('all_protocols')
955protocol_dirs = []
956Export('protocol_dirs')
957slicc_includes = []
958Export('slicc_includes')
959
960# Walk the tree and execute all SConsopts scripts that wil add to the
961# above variables
962if GetOption('verbose'):
963    print("Reading SConsopts")
964for bdir in [ base_dir ] + extras_dir_list:
965    if not isdir(bdir):
966        print("Error: directory '%s' does not exist" % bdir)
967        Exit(1)
968    for root, dirs, files in os.walk(bdir):
969        if 'SConsopts' in files:
970            if GetOption('verbose'):
971                print("Reading", joinpath(root, 'SConsopts'))
972            SConscript(joinpath(root, 'SConsopts'))
973
974all_isa_list.sort()
975all_gpu_isa_list.sort()
976
977sticky_vars.AddVariables(
978    EnumVariable('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
979    EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'hsail', all_gpu_isa_list),
980    ListVariable('CPU_MODELS', 'CPU models',
981                 sorted(n for n,m in CpuModel.dict.iteritems() if m.default),
982                 sorted(CpuModel.dict.keys())),
983    BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
984                 False),
985    BoolVariable('SS_COMPATIBLE_FP',
986                 'Make floating-point results compatible with SimpleScalar',
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('CP_ANNOTATE', 'Enable critical path annotation capability',
995                 False),
996    BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
997                 have_kvm),
998    BoolVariable('USE_TUNTAP',
999                 'Enable using a tap device to bridge to the host network',
1000                 have_tuntap),
1001    BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
1002    EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
1003                  all_protocols),
1004    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
1005                 backtrace_impls[-1], backtrace_impls)
1006    )
1007
1008# These variables get exported to #defines in config/*.hh (see src/SConscript).
1009export_vars += ['USE_FENV', 'SS_COMPATIBLE_FP', 'TARGET_ISA', 'TARGET_GPU_ISA',
1010                'CP_ANNOTATE', 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP',
1011                'PROTOCOL', 'HAVE_PROTOBUF', 'HAVE_PERF_ATTR_EXCLUDE_HOST',
1012                'USE_PNG']
1013
1014###################################################
1015#
1016# Define a SCons builder for configuration flag headers.
1017#
1018###################################################
1019
1020# This function generates a config header file that #defines the
1021# variable symbol to the current variable setting (0 or 1).  The source
1022# operands are the name of the variable and a Value node containing the
1023# value of the variable.
1024def build_config_file(target, source, env):
1025    (variable, value) = [s.get_contents() for s in source]
1026    f = file(str(target[0]), 'w')
1027    print('#define', variable, value, file=f)
1028    f.close()
1029    return None
1030
1031# Combine the two functions into a scons Action object.
1032config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1033
1034# The emitter munges the source & target node lists to reflect what
1035# we're really doing.
1036def config_emitter(target, source, env):
1037    # extract variable name from Builder arg
1038    variable = str(target[0])
1039    # True target is config header file
1040    target = joinpath('config', variable.lower() + '.hh')
1041    val = env[variable]
1042    if isinstance(val, bool):
1043        # Force value to 0/1
1044        val = int(val)
1045    elif isinstance(val, str):
1046        val = '"' + val + '"'
1047
1048    # Sources are variable name & value (packaged in SCons Value nodes)
1049    return ([target], [Value(variable), Value(val)])
1050
1051config_builder = Builder(emitter = config_emitter, action = config_action)
1052
1053main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1054
1055###################################################
1056#
1057# Builders for static and shared partially linked object files.
1058#
1059###################################################
1060
1061partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1062                                 src_suffix='$OBJSUFFIX',
1063                                 src_builder=['StaticObject', 'Object'],
1064                                 LINKFLAGS='$PLINKFLAGS',
1065                                 LIBS='')
1066
1067def partial_shared_emitter(target, source, env):
1068    for tgt in target:
1069        tgt.attributes.shared = 1
1070    return (target, source)
1071partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1072                                 emitter=partial_shared_emitter,
1073                                 src_suffix='$SHOBJSUFFIX',
1074                                 src_builder='SharedObject',
1075                                 SHLINKFLAGS='$PSHLINKFLAGS',
1076                                 LIBS='')
1077
1078main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1079                         'PartialStatic' : partial_static_builder })
1080
1081# builds in ext are shared across all configs in the build root.
1082ext_dir = abspath(joinpath(str(main.root), 'ext'))
1083ext_build_dirs = []
1084for root, dirs, files in os.walk(ext_dir):
1085    if 'SConscript' in files:
1086        build_dir = os.path.relpath(root, ext_dir)
1087        ext_build_dirs.append(build_dir)
1088        main.SConscript(joinpath(root, 'SConscript'),
1089                        variant_dir=joinpath(build_root, build_dir))
1090
1091main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
1092
1093###################################################
1094#
1095# This builder and wrapper method are used to set up a directory with
1096# switching headers. Those are headers which are in a generic location and
1097# that include more specific headers from a directory chosen at build time
1098# based on the current build settings.
1099#
1100###################################################
1101
1102def build_switching_header(target, source, env):
1103    path = str(target[0])
1104    subdir = str(source[0])
1105    dp, fp = os.path.split(path)
1106    dp = os.path.relpath(os.path.realpath(dp),
1107                         os.path.realpath(env['BUILDDIR']))
1108    with open(path, 'w') as hdr:
1109        print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1110
1111switching_header_action = MakeAction(build_switching_header,
1112                                     Transform('GENERATE'))
1113
1114switching_header_builder = Builder(action=switching_header_action,
1115                                   source_factory=Value,
1116                                   single_source=True)
1117
1118main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1119
1120def switching_headers(self, headers, source):
1121    for header in headers:
1122        self.SwitchingHeader(header, source)
1123
1124main.AddMethod(switching_headers, 'SwitchingHeaders')
1125
1126###################################################
1127#
1128# Define build environments for selected configurations.
1129#
1130###################################################
1131
1132for variant_path in variant_paths:
1133    if not GetOption('silent'):
1134        print("Building in", variant_path)
1135
1136    # Make a copy of the build-root environment to use for this config.
1137    env = main.Clone()
1138    env['BUILDDIR'] = variant_path
1139
1140    # variant_dir is the tail component of build path, and is used to
1141    # determine the build parameters (e.g., 'ALPHA_SE')
1142    (build_root, variant_dir) = splitpath(variant_path)
1143
1144    # Set env variables according to the build directory config.
1145    sticky_vars.files = []
1146    # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1147    # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1148    # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1149    current_vars_file = joinpath(build_root, 'variables', variant_dir)
1150    if isfile(current_vars_file):
1151        sticky_vars.files.append(current_vars_file)
1152        if not GetOption('silent'):
1153            print("Using saved variables file %s" % current_vars_file)
1154    elif variant_dir in ext_build_dirs:
1155        # Things in ext are built without a variant directory.
1156        continue
1157    else:
1158        # Build dir-specific variables file doesn't exist.
1159
1160        # Make sure the directory is there so we can create it later
1161        opt_dir = dirname(current_vars_file)
1162        if not isdir(opt_dir):
1163            mkdir(opt_dir)
1164
1165        # Get default build variables from source tree.  Variables are
1166        # normally determined by name of $VARIANT_DIR, but can be
1167        # overridden by '--default=' arg on command line.
1168        default = GetOption('default')
1169        opts_dir = joinpath(main.root.abspath, 'build_opts')
1170        if default:
1171            default_vars_files = [joinpath(build_root, 'variables', default),
1172                                  joinpath(opts_dir, default)]
1173        else:
1174            default_vars_files = [joinpath(opts_dir, variant_dir)]
1175        existing_files = filter(isfile, default_vars_files)
1176        if existing_files:
1177            default_vars_file = existing_files[0]
1178            sticky_vars.files.append(default_vars_file)
1179            print("Variables file %s not found,\n  using defaults in %s"
1180                  % (current_vars_file, default_vars_file))
1181        else:
1182            print("Error: cannot find variables file %s or "
1183                  "default file(s) %s"
1184                  % (current_vars_file, ' or '.join(default_vars_files)))
1185            Exit(1)
1186
1187    # Apply current variable settings to env
1188    sticky_vars.Update(env)
1189
1190    help_texts["local_vars"] += \
1191        "Build variables for %s:\n" % variant_dir \
1192                 + sticky_vars.GenerateHelpText(env)
1193
1194    # Process variable settings.
1195
1196    if not have_fenv and env['USE_FENV']:
1197        print("Warning: <fenv.h> not available; "
1198              "forcing USE_FENV to False in", variant_dir + ".")
1199        env['USE_FENV'] = False
1200
1201    if not env['USE_FENV']:
1202        print("Warning: No IEEE FP rounding mode control in",
1203              variant_dir + ".")
1204        print("         FP results may deviate slightly from other platforms.")
1205
1206    if not have_png and env['USE_PNG']:
1207        print("Warning: <png.h> not available; "
1208              "forcing USE_PNG to False in", variant_dir + ".")
1209        env['USE_PNG'] = False
1210
1211    if env['USE_PNG']:
1212        env.Append(LIBS=['png'])
1213
1214    if env['EFENCE']:
1215        env.Append(LIBS=['efence'])
1216
1217    if env['USE_KVM']:
1218        if not have_kvm:
1219            print("Warning: Can not enable KVM, host seems to "
1220                  "lack KVM support")
1221            env['USE_KVM'] = False
1222        elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1223            print("Info: KVM support disabled due to unsupported host and "
1224                  "target ISA combination")
1225            env['USE_KVM'] = False
1226
1227    if env['USE_TUNTAP']:
1228        if not have_tuntap:
1229            print("Warning: Can't connect EtherTap with a tap device.")
1230            env['USE_TUNTAP'] = False
1231
1232    if env['BUILD_GPU']:
1233        env.Append(CPPDEFINES=['BUILD_GPU'])
1234
1235    # Warn about missing optional functionality
1236    if env['USE_KVM']:
1237        if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1238            print("Warning: perf_event headers lack support for the "
1239                  "exclude_host attribute. KVM instruction counts will "
1240                  "be inaccurate.")
1241
1242    # Save sticky variable settings back to current variables file
1243    sticky_vars.Save(current_vars_file, env)
1244
1245    if env['USE_SSE2']:
1246        env.Append(CCFLAGS=['-msse2'])
1247
1248    # The src/SConscript file sets up the build rules in 'env' according
1249    # to the configured variables.  It returns a list of environments,
1250    # one for each variant build (debug, opt, etc.)
1251    SConscript('src/SConscript', variant_dir = variant_path, exports = 'env')
1252
1253# base help text
1254Help('''
1255Usage: scons [scons options] [build variables] [target(s)]
1256
1257Extra scons options:
1258%(options)s
1259
1260Global build variables:
1261%(global_vars)s
1262
1263%(local_vars)s
1264''' % help_texts)
1265