SConstruct revision 12920
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: Check failed for Python.h header in", py_includes)
750        print("Two possible reasons:")
751        print("1. Python headers are not installed (You can install the "
752              "package python-dev on Ubuntu and RedHat)")
753        print("2. SCons is using a wrong C compiler. This can happen if "
754              "CC has the wrong value.")
755        print("CC = %s" % main['CC'])
756        Exit(1)
757
758    for lib in py_libs:
759        if not conf.CheckLib(lib):
760            print("Error: can't find library %s required by python" % lib)
761            Exit(1)
762
763# On Solaris you need to use libsocket for socket ops
764if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
765   if not conf.CheckLibWithHeader('socket', 'sys/socket.h', 'C++', 'accept(0,0,0);'):
766       print("Can't find library with socket calls (e.g. accept())")
767       Exit(1)
768
769# Check for zlib.  If the check passes, libz will be automatically
770# added to the LIBS environment variable.
771if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
772    print('Error: did not find needed zlib compression library '
773          'and/or zlib.h header file.')
774    print('       Please install zlib and try again.')
775    Exit(1)
776
777# If we have the protobuf compiler, also make sure we have the
778# development libraries. If the check passes, libprotobuf will be
779# automatically added to the LIBS environment variable. After
780# this, we can use the HAVE_PROTOBUF flag to determine if we have
781# got both protoc and libprotobuf available.
782main['HAVE_PROTOBUF'] = main['PROTOC'] and \
783    conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
784                            'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
785
786# Valgrind gets much less confused if you tell it when you're using
787# alternative stacks.
788main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
789
790# If we have the compiler but not the library, print another warning.
791if main['PROTOC'] and not main['HAVE_PROTOBUF']:
792    print(termcap.Yellow + termcap.Bold +
793        'Warning: did not find protocol buffer library and/or headers.\n' +
794    '       Please install libprotobuf-dev for tracing support.' +
795    termcap.Normal)
796
797# Check for librt.
798have_posix_clock = \
799    conf.CheckLibWithHeader(None, 'time.h', 'C',
800                            'clock_nanosleep(0,0,NULL,NULL);') or \
801    conf.CheckLibWithHeader('rt', 'time.h', 'C',
802                            'clock_nanosleep(0,0,NULL,NULL);')
803
804have_posix_timers = \
805    conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
806                            'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
807
808if not GetOption('without_tcmalloc'):
809    if conf.CheckLib('tcmalloc'):
810        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
811    elif conf.CheckLib('tcmalloc_minimal'):
812        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
813    else:
814        print(termcap.Yellow + termcap.Bold +
815              "You can get a 12% performance improvement by "
816              "installing tcmalloc (libgoogle-perftools-dev package "
817              "on Ubuntu or RedHat)." + termcap.Normal)
818
819
820# Detect back trace implementations. The last implementation in the
821# list will be used by default.
822backtrace_impls = [ "none" ]
823
824backtrace_checker = 'char temp;' + \
825    ' backtrace_symbols_fd((void*)&temp, 0, 0);'
826if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
827    backtrace_impls.append("glibc")
828elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
829                             backtrace_checker):
830    # NetBSD and FreeBSD need libexecinfo.
831    backtrace_impls.append("glibc")
832    main.Append(LIBS=['execinfo'])
833
834if backtrace_impls[-1] == "none":
835    default_backtrace_impl = "none"
836    print(termcap.Yellow + termcap.Bold +
837        "No suitable back trace implementation found." +
838        termcap.Normal)
839
840if not have_posix_clock:
841    print("Can't find library for POSIX clocks.")
842
843# Check for <fenv.h> (C99 FP environment control)
844have_fenv = conf.CheckHeader('fenv.h', '<>')
845if not have_fenv:
846    print("Warning: Header file <fenv.h> not found.")
847    print("         This host has no IEEE FP rounding mode control.")
848
849# Check for <png.h> (libpng library needed if wanting to dump
850# frame buffer image in png format)
851have_png = conf.CheckHeader('png.h', '<>')
852if not have_png:
853    print("Warning: Header file <png.h> not found.")
854    print("         This host has no libpng library.")
855    print("         Disabling support for PNG framebuffers.")
856
857# Check if we should enable KVM-based hardware virtualization. The API
858# we rely on exists since version 2.6.36 of the kernel, but somehow
859# the KVM_API_VERSION does not reflect the change. We test for one of
860# the types as a fall back.
861have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
862if not have_kvm:
863    print("Info: Compatible header file <linux/kvm.h> not found, "
864          "disabling KVM support.")
865
866# Check if the TUN/TAP driver is available.
867have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
868if not have_tuntap:
869    print("Info: Compatible header file <linux/if_tun.h> not found.")
870
871# x86 needs support for xsave. We test for the structure here since we
872# won't be able to run new tests by the time we know which ISA we're
873# targeting.
874have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
875                                    '#include <linux/kvm.h>') != 0
876
877# Check if the requested target ISA is compatible with the host
878def is_isa_kvm_compatible(isa):
879    try:
880        import platform
881        host_isa = platform.machine()
882    except:
883        print("Warning: Failed to determine host ISA.")
884        return False
885
886    if not have_posix_timers:
887        print("Warning: Can not enable KVM, host seems to lack support "
888              "for POSIX timers")
889        return False
890
891    if isa == "arm":
892        return host_isa in ( "armv7l", "aarch64" )
893    elif isa == "x86":
894        if host_isa != "x86_64":
895            return False
896
897        if not have_kvm_xsave:
898            print("KVM on x86 requires xsave support in kernel headers.")
899            return False
900
901        return True
902    else:
903        return False
904
905
906# Check if the exclude_host attribute is available. We want this to
907# get accurate instruction counts in KVM.
908main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
909    'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
910
911
912######################################################################
913#
914# Finish the configuration
915#
916main = conf.Finish()
917
918######################################################################
919#
920# Collect all non-global variables
921#
922
923# Define the universe of supported ISAs
924all_isa_list = [ ]
925all_gpu_isa_list = [ ]
926Export('all_isa_list')
927Export('all_gpu_isa_list')
928
929class CpuModel(object):
930    '''The CpuModel class encapsulates everything the ISA parser needs to
931    know about a particular CPU model.'''
932
933    # Dict of available CPU model objects.  Accessible as CpuModel.dict.
934    dict = {}
935
936    # Constructor.  Automatically adds models to CpuModel.dict.
937    def __init__(self, name, default=False):
938        self.name = name           # name of model
939
940        # This cpu is enabled by default
941        self.default = default
942
943        # Add self to dict
944        if name in CpuModel.dict:
945            raise AttributeError, "CpuModel '%s' already registered" % name
946        CpuModel.dict[name] = self
947
948Export('CpuModel')
949
950# Sticky variables get saved in the variables file so they persist from
951# one invocation to the next (unless overridden, in which case the new
952# value becomes sticky).
953sticky_vars = Variables(args=ARGUMENTS)
954Export('sticky_vars')
955
956# Sticky variables that should be exported
957export_vars = []
958Export('export_vars')
959
960# For Ruby
961all_protocols = []
962Export('all_protocols')
963protocol_dirs = []
964Export('protocol_dirs')
965slicc_includes = []
966Export('slicc_includes')
967
968# Walk the tree and execute all SConsopts scripts that wil add to the
969# above variables
970if GetOption('verbose'):
971    print("Reading SConsopts")
972for bdir in [ base_dir ] + extras_dir_list:
973    if not isdir(bdir):
974        print("Error: directory '%s' does not exist" % bdir)
975        Exit(1)
976    for root, dirs, files in os.walk(bdir):
977        if 'SConsopts' in files:
978            if GetOption('verbose'):
979                print("Reading", joinpath(root, 'SConsopts'))
980            SConscript(joinpath(root, 'SConsopts'))
981
982all_isa_list.sort()
983all_gpu_isa_list.sort()
984
985sticky_vars.AddVariables(
986    EnumVariable('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
987    EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'hsail', all_gpu_isa_list),
988    ListVariable('CPU_MODELS', 'CPU models',
989                 sorted(n for n,m in CpuModel.dict.iteritems() if m.default),
990                 sorted(CpuModel.dict.keys())),
991    BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
992                 False),
993    BoolVariable('SS_COMPATIBLE_FP',
994                 'Make floating-point results compatible with SimpleScalar',
995                 False),
996    BoolVariable('USE_SSE2',
997                 'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
998                 False),
999    BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
1000    BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
1001    BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
1002    BoolVariable('CP_ANNOTATE', 'Enable critical path annotation capability',
1003                 False),
1004    BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
1005                 have_kvm),
1006    BoolVariable('USE_TUNTAP',
1007                 'Enable using a tap device to bridge to the host network',
1008                 have_tuntap),
1009    BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
1010    EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
1011                  all_protocols),
1012    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
1013                 backtrace_impls[-1], backtrace_impls)
1014    )
1015
1016# These variables get exported to #defines in config/*.hh (see src/SConscript).
1017export_vars += ['USE_FENV', 'SS_COMPATIBLE_FP', 'TARGET_ISA', 'TARGET_GPU_ISA',
1018                'CP_ANNOTATE', 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP',
1019                'PROTOCOL', 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
1020                'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG']
1021
1022###################################################
1023#
1024# Define a SCons builder for configuration flag headers.
1025#
1026###################################################
1027
1028# This function generates a config header file that #defines the
1029# variable symbol to the current variable setting (0 or 1).  The source
1030# operands are the name of the variable and a Value node containing the
1031# value of the variable.
1032def build_config_file(target, source, env):
1033    (variable, value) = [s.get_contents() for s in source]
1034    f = file(str(target[0]), 'w')
1035    print('#define', variable, value, file=f)
1036    f.close()
1037    return None
1038
1039# Combine the two functions into a scons Action object.
1040config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1041
1042# The emitter munges the source & target node lists to reflect what
1043# we're really doing.
1044def config_emitter(target, source, env):
1045    # extract variable name from Builder arg
1046    variable = str(target[0])
1047    # True target is config header file
1048    target = joinpath('config', variable.lower() + '.hh')
1049    val = env[variable]
1050    if isinstance(val, bool):
1051        # Force value to 0/1
1052        val = int(val)
1053    elif isinstance(val, str):
1054        val = '"' + val + '"'
1055
1056    # Sources are variable name & value (packaged in SCons Value nodes)
1057    return ([target], [Value(variable), Value(val)])
1058
1059config_builder = Builder(emitter = config_emitter, action = config_action)
1060
1061main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1062
1063###################################################
1064#
1065# Builders for static and shared partially linked object files.
1066#
1067###################################################
1068
1069partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1070                                 src_suffix='$OBJSUFFIX',
1071                                 src_builder=['StaticObject', 'Object'],
1072                                 LINKFLAGS='$PLINKFLAGS',
1073                                 LIBS='')
1074
1075def partial_shared_emitter(target, source, env):
1076    for tgt in target:
1077        tgt.attributes.shared = 1
1078    return (target, source)
1079partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1080                                 emitter=partial_shared_emitter,
1081                                 src_suffix='$SHOBJSUFFIX',
1082                                 src_builder='SharedObject',
1083                                 SHLINKFLAGS='$PSHLINKFLAGS',
1084                                 LIBS='')
1085
1086main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1087                         'PartialStatic' : partial_static_builder })
1088
1089# builds in ext are shared across all configs in the build root.
1090ext_dir = abspath(joinpath(str(main.root), 'ext'))
1091ext_build_dirs = []
1092for root, dirs, files in os.walk(ext_dir):
1093    if 'SConscript' in files:
1094        build_dir = os.path.relpath(root, ext_dir)
1095        ext_build_dirs.append(build_dir)
1096        main.SConscript(joinpath(root, 'SConscript'),
1097                        variant_dir=joinpath(build_root, build_dir))
1098
1099main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
1100
1101###################################################
1102#
1103# This builder and wrapper method are used to set up a directory with
1104# switching headers. Those are headers which are in a generic location and
1105# that include more specific headers from a directory chosen at build time
1106# based on the current build settings.
1107#
1108###################################################
1109
1110def build_switching_header(target, source, env):
1111    path = str(target[0])
1112    subdir = str(source[0])
1113    dp, fp = os.path.split(path)
1114    dp = os.path.relpath(os.path.realpath(dp),
1115                         os.path.realpath(env['BUILDDIR']))
1116    with open(path, 'w') as hdr:
1117        print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1118
1119switching_header_action = MakeAction(build_switching_header,
1120                                     Transform('GENERATE'))
1121
1122switching_header_builder = Builder(action=switching_header_action,
1123                                   source_factory=Value,
1124                                   single_source=True)
1125
1126main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1127
1128def switching_headers(self, headers, source):
1129    for header in headers:
1130        self.SwitchingHeader(header, source)
1131
1132main.AddMethod(switching_headers, 'SwitchingHeaders')
1133
1134###################################################
1135#
1136# Define build environments for selected configurations.
1137#
1138###################################################
1139
1140for variant_path in variant_paths:
1141    if not GetOption('silent'):
1142        print("Building in", variant_path)
1143
1144    # Make a copy of the build-root environment to use for this config.
1145    env = main.Clone()
1146    env['BUILDDIR'] = variant_path
1147
1148    # variant_dir is the tail component of build path, and is used to
1149    # determine the build parameters (e.g., 'ALPHA_SE')
1150    (build_root, variant_dir) = splitpath(variant_path)
1151
1152    # Set env variables according to the build directory config.
1153    sticky_vars.files = []
1154    # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1155    # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1156    # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1157    current_vars_file = joinpath(build_root, 'variables', variant_dir)
1158    if isfile(current_vars_file):
1159        sticky_vars.files.append(current_vars_file)
1160        if not GetOption('silent'):
1161            print("Using saved variables file %s" % current_vars_file)
1162    elif variant_dir in ext_build_dirs:
1163        # Things in ext are built without a variant directory.
1164        continue
1165    else:
1166        # Build dir-specific variables file doesn't exist.
1167
1168        # Make sure the directory is there so we can create it later
1169        opt_dir = dirname(current_vars_file)
1170        if not isdir(opt_dir):
1171            mkdir(opt_dir)
1172
1173        # Get default build variables from source tree.  Variables are
1174        # normally determined by name of $VARIANT_DIR, but can be
1175        # overridden by '--default=' arg on command line.
1176        default = GetOption('default')
1177        opts_dir = joinpath(main.root.abspath, 'build_opts')
1178        if default:
1179            default_vars_files = [joinpath(build_root, 'variables', default),
1180                                  joinpath(opts_dir, default)]
1181        else:
1182            default_vars_files = [joinpath(opts_dir, variant_dir)]
1183        existing_files = filter(isfile, default_vars_files)
1184        if existing_files:
1185            default_vars_file = existing_files[0]
1186            sticky_vars.files.append(default_vars_file)
1187            print("Variables file %s not found,\n  using defaults in %s"
1188                  % (current_vars_file, default_vars_file))
1189        else:
1190            print("Error: cannot find variables file %s or "
1191                  "default file(s) %s"
1192                  % (current_vars_file, ' or '.join(default_vars_files)))
1193            Exit(1)
1194
1195    # Apply current variable settings to env
1196    sticky_vars.Update(env)
1197
1198    help_texts["local_vars"] += \
1199        "Build variables for %s:\n" % variant_dir \
1200                 + sticky_vars.GenerateHelpText(env)
1201
1202    # Process variable settings.
1203
1204    if not have_fenv and env['USE_FENV']:
1205        print("Warning: <fenv.h> not available; "
1206              "forcing USE_FENV to False in", variant_dir + ".")
1207        env['USE_FENV'] = False
1208
1209    if not env['USE_FENV']:
1210        print("Warning: No IEEE FP rounding mode control in",
1211              variant_dir + ".")
1212        print("         FP results may deviate slightly from other platforms.")
1213
1214    if not have_png and env['USE_PNG']:
1215        print("Warning: <png.h> not available; "
1216              "forcing USE_PNG to False in", variant_dir + ".")
1217        env['USE_PNG'] = False
1218
1219    if env['USE_PNG']:
1220        env.Append(LIBS=['png'])
1221
1222    if env['EFENCE']:
1223        env.Append(LIBS=['efence'])
1224
1225    if env['USE_KVM']:
1226        if not have_kvm:
1227            print("Warning: Can not enable KVM, host seems to "
1228                  "lack KVM support")
1229            env['USE_KVM'] = False
1230        elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1231            print("Info: KVM support disabled due to unsupported host and "
1232                  "target ISA combination")
1233            env['USE_KVM'] = False
1234
1235    if env['USE_TUNTAP']:
1236        if not have_tuntap:
1237            print("Warning: Can't connect EtherTap with a tap device.")
1238            env['USE_TUNTAP'] = False
1239
1240    if env['BUILD_GPU']:
1241        env.Append(CPPDEFINES=['BUILD_GPU'])
1242
1243    # Warn about missing optional functionality
1244    if env['USE_KVM']:
1245        if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1246            print("Warning: perf_event headers lack support for the "
1247                  "exclude_host attribute. KVM instruction counts will "
1248                  "be inaccurate.")
1249
1250    # Save sticky variable settings back to current variables file
1251    sticky_vars.Save(current_vars_file, env)
1252
1253    if env['USE_SSE2']:
1254        env.Append(CCFLAGS=['-msse2'])
1255
1256    # The src/SConscript file sets up the build rules in 'env' according
1257    # to the configured variables.  It returns a list of environments,
1258    # one for each variant build (debug, opt, etc.)
1259    SConscript('src/SConscript', variant_dir = variant_path, exports = 'env')
1260
1261# base help text
1262Help('''
1263Usage: scons [scons options] [build variables] [target(s)]
1264
1265Extra scons options:
1266%(options)s
1267
1268Global build variables:
1269%(global_vars)s
1270
1271%(local_vars)s
1272''' % help_texts)
1273