SConstruct revision 13715
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
95from re import match
96
97# SCons includes
98import SCons
99import SCons.Node
100
101from m5.util import compareVersions, readCommand
102
103help_texts = {
104    "options" : "",
105    "global_vars" : "",
106    "local_vars" : ""
107}
108
109Export("help_texts")
110
111
112# There's a bug in scons in that (1) by default, the help texts from
113# AddOption() are supposed to be displayed when you type 'scons -h'
114# and (2) you can override the help displayed by 'scons -h' using the
115# Help() function, but these two features are incompatible: once
116# you've overridden the help text using Help(), there's no way to get
117# at the help texts from AddOptions.  See:
118#     http://scons.tigris.org/issues/show_bug.cgi?id=2356
119#     http://scons.tigris.org/issues/show_bug.cgi?id=2611
120# This hack lets us extract the help text from AddOptions and
121# re-inject it via Help().  Ideally someday this bug will be fixed and
122# we can just use AddOption directly.
123def AddLocalOption(*args, **kwargs):
124    col_width = 30
125
126    help = "  " + ", ".join(args)
127    if "help" in kwargs:
128        length = len(help)
129        if length >= col_width:
130            help += "\n" + " " * col_width
131        else:
132            help += " " * (col_width - length)
133        help += kwargs["help"]
134    help_texts["options"] += help + "\n"
135
136    AddOption(*args, **kwargs)
137
138AddLocalOption('--colors', dest='use_colors', action='store_true',
139               help="Add color to abbreviated scons output")
140AddLocalOption('--no-colors', dest='use_colors', action='store_false',
141               help="Don't add color to abbreviated scons output")
142AddLocalOption('--with-cxx-config', dest='with_cxx_config',
143               action='store_true',
144               help="Build with support for C++-based configuration")
145AddLocalOption('--default', dest='default', type='string', action='store',
146               help='Override which build_opts file to use for defaults')
147AddLocalOption('--ignore-style', dest='ignore_style', action='store_true',
148               help='Disable style checking hooks')
149AddLocalOption('--gold-linker', dest='gold_linker', action='store_true',
150               help='Use the gold linker')
151AddLocalOption('--no-lto', dest='no_lto', action='store_true',
152               help='Disable Link-Time Optimization for fast')
153AddLocalOption('--force-lto', dest='force_lto', action='store_true',
154               help='Use Link-Time Optimization instead of partial linking' +
155                    ' when the compiler doesn\'t support using them together.')
156AddLocalOption('--update-ref', dest='update_ref', action='store_true',
157               help='Update test reference outputs')
158AddLocalOption('--verbose', dest='verbose', action='store_true',
159               help='Print full tool command lines')
160AddLocalOption('--without-python', dest='without_python',
161               action='store_true',
162               help='Build without Python configuration support')
163AddLocalOption('--without-tcmalloc', dest='without_tcmalloc',
164               action='store_true',
165               help='Disable linking against tcmalloc')
166AddLocalOption('--with-ubsan', dest='with_ubsan', action='store_true',
167               help='Build with Undefined Behavior Sanitizer if available')
168AddLocalOption('--with-asan', dest='with_asan', action='store_true',
169               help='Build with Address Sanitizer if available')
170
171if GetOption('no_lto') and GetOption('force_lto'):
172    print('--no-lto and --force-lto are mutually exclusive')
173    Exit(1)
174
175########################################################################
176#
177# Set up the main build environment.
178#
179########################################################################
180
181main = Environment()
182
183from gem5_scons import Transform
184from gem5_scons.util import get_termcap
185termcap = get_termcap()
186
187main_dict_keys = main.Dictionary().keys()
188
189# Check that we have a C/C++ compiler
190if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
191    print("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
192    Exit(1)
193
194###################################################
195#
196# Figure out which configurations to set up based on the path(s) of
197# the target(s).
198#
199###################################################
200
201# Find default configuration & binary.
202Default(environ.get('M5_DEFAULT_BINARY', 'build/ALPHA/gem5.debug'))
203
204# helper function: find last occurrence of element in list
205def rfind(l, elt, offs = -1):
206    for i in range(len(l)+offs, 0, -1):
207        if l[i] == elt:
208            return i
209    raise ValueError, "element not found"
210
211# Take a list of paths (or SCons Nodes) and return a list with all
212# paths made absolute and ~-expanded.  Paths will be interpreted
213# relative to the launch directory unless a different root is provided
214def makePathListAbsolute(path_list, root=GetLaunchDir()):
215    return [abspath(joinpath(root, expanduser(str(p))))
216            for p in path_list]
217
218def find_first_prog(prog_names):
219    """Find the absolute path to the first existing binary in prog_names"""
220
221    if not isinstance(prog_names, (list, tuple)):
222        prog_names = [ prog_names ]
223
224    for p in prog_names:
225        p = main.WhereIs(p)
226        if p is not None:
227            return p
228
229    return None
230
231# Each target must have 'build' in the interior of the path; the
232# directory below this will determine the build parameters.  For
233# example, for target 'foo/bar/build/ALPHA_SE/arch/alpha/blah.do' we
234# recognize that ALPHA_SE specifies the configuration because it
235# follow 'build' in the build path.
236
237# The funky assignment to "[:]" is needed to replace the list contents
238# in place rather than reassign the symbol to a new list, which
239# doesn't work (obviously!).
240BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
241
242# Generate a list of the unique build roots and configs that the
243# collected targets reference.
244variant_paths = []
245build_root = None
246for t in BUILD_TARGETS:
247    path_dirs = t.split('/')
248    try:
249        build_top = rfind(path_dirs, 'build', -2)
250    except:
251        print("Error: no non-leaf 'build' dir found on target path", t)
252        Exit(1)
253    this_build_root = joinpath('/',*path_dirs[:build_top+1])
254    if not build_root:
255        build_root = this_build_root
256    else:
257        if this_build_root != build_root:
258            print("Error: build targets not under same build root\n"
259                  "  %s\n  %s" % (build_root, this_build_root))
260            Exit(1)
261    variant_path = joinpath('/',*path_dirs[:build_top+2])
262    if variant_path not in variant_paths:
263        variant_paths.append(variant_path)
264
265# Make sure build_root exists (might not if this is the first build there)
266if not isdir(build_root):
267    mkdir(build_root)
268main['BUILDROOT'] = build_root
269
270Export('main')
271
272main.SConsignFile(joinpath(build_root, "sconsign"))
273
274# Default duplicate option is to use hard links, but this messes up
275# when you use emacs to edit a file in the target dir, as emacs moves
276# file to file~ then copies to file, breaking the link.  Symbolic
277# (soft) links work better.
278main.SetOption('duplicate', 'soft-copy')
279
280#
281# Set up global sticky variables... these are common to an entire build
282# tree (not specific to a particular build like ALPHA_SE)
283#
284
285global_vars_file = joinpath(build_root, 'variables.global')
286
287global_vars = Variables(global_vars_file, args=ARGUMENTS)
288
289global_vars.AddVariables(
290    ('CC', 'C compiler', environ.get('CC', main['CC'])),
291    ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
292    ('PYTHON_CONFIG', 'Python config binary to use',
293     [ 'python2.7-config', 'python-config' ]),
294    ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
295    ('BATCH', 'Use batch pool for build and tests', False),
296    ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
297    ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
298    ('EXTRAS', 'Add extra directories to the compilation', '')
299    )
300
301# Update main environment with values from ARGUMENTS & global_vars_file
302global_vars.Update(main)
303help_texts["global_vars"] += global_vars.GenerateHelpText(main)
304
305# Save sticky variable settings back to current variables file
306global_vars.Save(global_vars_file, main)
307
308# Parse EXTRAS variable to build list of all directories where we're
309# look for sources etc.  This list is exported as extras_dir_list.
310base_dir = main.srcdir.abspath
311if main['EXTRAS']:
312    extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
313else:
314    extras_dir_list = []
315
316Export('base_dir')
317Export('extras_dir_list')
318
319# the ext directory should be on the #includes path
320main.Append(CPPPATH=[Dir('ext')])
321
322# Add shared top-level headers
323main.Prepend(CPPPATH=Dir('include'))
324
325if GetOption('verbose'):
326    def MakeAction(action, string, *args, **kwargs):
327        return Action(action, *args, **kwargs)
328else:
329    MakeAction = Action
330    main['CCCOMSTR']        = Transform("CC")
331    main['CXXCOMSTR']       = Transform("CXX")
332    main['ASCOMSTR']        = Transform("AS")
333    main['ARCOMSTR']        = Transform("AR", 0)
334    main['LINKCOMSTR']      = Transform("LINK", 0)
335    main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
336    main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
337    main['M4COMSTR']        = Transform("M4")
338    main['SHCCCOMSTR']      = Transform("SHCC")
339    main['SHCXXCOMSTR']     = Transform("SHCXX")
340Export('MakeAction')
341
342# Initialize the Link-Time Optimization (LTO) flags
343main['LTO_CCFLAGS'] = []
344main['LTO_LDFLAGS'] = []
345
346# According to the readme, tcmalloc works best if the compiler doesn't
347# assume that we're using the builtin malloc and friends. These flags
348# are compiler-specific, so we need to set them after we detect which
349# compiler we're using.
350main['TCMALLOC_CCFLAGS'] = []
351
352CXX_version = readCommand([main['CXX'],'--version'], exception=False)
353CXX_V = readCommand([main['CXX'],'-V'], exception=False)
354
355main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
356main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
357if main['GCC'] + main['CLANG'] > 1:
358    print('Error: How can we have two at the same time?')
359    Exit(1)
360
361# Set up default C++ compiler flags
362if main['GCC'] or main['CLANG']:
363    # As gcc and clang share many flags, do the common parts here
364    main.Append(CCFLAGS=['-pipe'])
365    main.Append(CCFLAGS=['-fno-strict-aliasing'])
366    # Enable -Wall and -Wextra and then disable the few warnings that
367    # we consistently violate
368    main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
369                         '-Wno-sign-compare', '-Wno-unused-parameter'])
370    # We always compile using C++11
371    main.Append(CXXFLAGS=['-std=c++11'])
372    if sys.platform.startswith('freebsd'):
373        main.Append(CCFLAGS=['-I/usr/local/include'])
374        main.Append(CXXFLAGS=['-I/usr/local/include'])
375
376    main['FILTER_PSHLINKFLAGS'] = lambda x: str(x).replace(' -shared', '')
377    main['PSHLINKFLAGS'] = main.subst('${FILTER_PSHLINKFLAGS(SHLINKFLAGS)}')
378    if GetOption('gold_linker'):
379        main.Append(LINKFLAGS='-fuse-ld=gold')
380    main['PLINKFLAGS'] = main.subst('${LINKFLAGS}')
381    shared_partial_flags = ['-r', '-nostdlib']
382    main.Append(PSHLINKFLAGS=shared_partial_flags)
383    main.Append(PLINKFLAGS=shared_partial_flags)
384
385    # Treat warnings as errors but white list some warnings that we
386    # want to allow (e.g., deprecation warnings).
387    main.Append(CCFLAGS=['-Werror',
388                         '-Wno-error=deprecated-declarations',
389                         '-Wno-error=deprecated',
390                        ])
391else:
392    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
393    print("Don't know what compiler options to use for your compiler.")
394    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
395    print(termcap.Yellow + '       version:' + termcap.Normal, end = ' ')
396    if not CXX_version:
397        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
398              termcap.Normal)
399    else:
400        print(CXX_version.replace('\n', '<nl>'))
401    print("       If you're trying to use a compiler other than GCC")
402    print("       or clang, there appears to be something wrong with your")
403    print("       environment.")
404    print("       ")
405    print("       If you are trying to use a compiler other than those listed")
406    print("       above you will need to ease fix SConstruct and ")
407    print("       src/SConscript to support that compiler.")
408    Exit(1)
409
410if main['GCC']:
411    # Check for a supported version of gcc. >= 4.8 is chosen for its
412    # level of c++11 support. See
413    # http://gcc.gnu.org/projects/cxx0x.html for details.
414    gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
415    if compareVersions(gcc_version, "4.8") < 0:
416        print('Error: gcc version 4.8 or newer required.')
417        print('       Installed version: ', gcc_version)
418        Exit(1)
419
420    main['GCC_VERSION'] = gcc_version
421
422    if compareVersions(gcc_version, '4.9') >= 0:
423        # Incremental linking with LTO is currently broken in gcc versions
424        # 4.9 and above. A version where everything works completely hasn't
425        # yet been identified.
426        #
427        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548
428        main['BROKEN_INCREMENTAL_LTO'] = True
429    if compareVersions(gcc_version, '6.0') >= 0:
430        # gcc versions 6.0 and greater accept an -flinker-output flag which
431        # selects what type of output the linker should generate. This is
432        # necessary for incremental lto to work, but is also broken in
433        # current versions of gcc. It may not be necessary in future
434        # versions. We add it here since it might be, and as a reminder that
435        # it exists. It's excluded if lto is being forced.
436        #
437        # https://gcc.gnu.org/gcc-6/changes.html
438        # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html
439        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866
440        if not GetOption('force_lto'):
441            main.Append(PSHLINKFLAGS='-flinker-output=rel')
442            main.Append(PLINKFLAGS='-flinker-output=rel')
443
444    # Make sure we warn if the user has requested to compile with the
445    # Undefined Benahvior Sanitizer and this version of gcc does not
446    # support it.
447    if GetOption('with_ubsan') and \
448            compareVersions(gcc_version, '4.9') < 0:
449        print(termcap.Yellow + termcap.Bold +
450            'Warning: UBSan is only supported using gcc 4.9 and later.' +
451            termcap.Normal)
452
453    disable_lto = GetOption('no_lto')
454    if not disable_lto and main.get('BROKEN_INCREMENTAL_LTO', False) and \
455            not GetOption('force_lto'):
456        print(termcap.Yellow + termcap.Bold +
457            'Warning: Your compiler doesn\'t support incremental linking' +
458            ' and lto at the same time, so lto is being disabled. To force' +
459            ' lto on anyway, use the --force-lto option. That will disable' +
460            ' partial linking.' +
461            termcap.Normal)
462        disable_lto = True
463
464    # Add the appropriate Link-Time Optimization (LTO) flags
465    # unless LTO is explicitly turned off. Note that these flags
466    # are only used by the fast target.
467    if not disable_lto:
468        # Pass the LTO flag when compiling to produce GIMPLE
469        # output, we merely create the flags here and only append
470        # them later
471        main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
472
473        # Use the same amount of jobs for LTO as we are running
474        # scons with
475        main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
476
477    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
478                                  '-fno-builtin-realloc', '-fno-builtin-free'])
479
480    # The address sanitizer is available for gcc >= 4.8
481    if GetOption('with_asan'):
482        if GetOption('with_ubsan') and \
483                compareVersions(main['GCC_VERSION'], '4.9') >= 0:
484            main.Append(CCFLAGS=['-fsanitize=address,undefined',
485                                 '-fno-omit-frame-pointer'],
486                        LINKFLAGS='-fsanitize=address,undefined')
487        else:
488            main.Append(CCFLAGS=['-fsanitize=address',
489                                 '-fno-omit-frame-pointer'],
490                        LINKFLAGS='-fsanitize=address')
491    # Only gcc >= 4.9 supports UBSan, so check both the version
492    # and the command-line option before adding the compiler and
493    # linker flags.
494    elif GetOption('with_ubsan') and \
495            compareVersions(main['GCC_VERSION'], '4.9') >= 0:
496        main.Append(CCFLAGS='-fsanitize=undefined')
497        main.Append(LINKFLAGS='-fsanitize=undefined')
498
499elif main['CLANG']:
500    # Check for a supported version of clang, >= 3.1 is needed to
501    # support similar features as gcc 4.8. See
502    # http://clang.llvm.org/cxx_status.html for details
503    clang_version_re = re.compile(".* version (\d+\.\d+)")
504    clang_version_match = clang_version_re.search(CXX_version)
505    if (clang_version_match):
506        clang_version = clang_version_match.groups()[0]
507        if compareVersions(clang_version, "3.1") < 0:
508            print('Error: clang version 3.1 or newer required.')
509            print('       Installed version:', clang_version)
510            Exit(1)
511    else:
512        print('Error: Unable to determine clang version.')
513        Exit(1)
514
515    # clang has a few additional warnings that we disable, extraneous
516    # parantheses are allowed due to Ruby's printing of the AST,
517    # finally self assignments are allowed as the generated CPU code
518    # is relying on this
519    main.Append(CCFLAGS=['-Wno-parentheses',
520                         '-Wno-self-assign',
521                         # Some versions of libstdc++ (4.8?) seem to
522                         # use struct hash and class hash
523                         # interchangeably.
524                         '-Wno-mismatched-tags',
525                         ])
526
527    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin'])
528
529    # On Mac OS X/Darwin we need to also use libc++ (part of XCode) as
530    # opposed to libstdc++, as the later is dated.
531    if sys.platform == "darwin":
532        main.Append(CXXFLAGS=['-stdlib=libc++'])
533        main.Append(LIBS=['c++'])
534
535    # On FreeBSD we need libthr.
536    if sys.platform.startswith('freebsd'):
537        main.Append(LIBS=['thr'])
538
539    # We require clang >= 3.1, so there is no need to check any
540    # versions here.
541    if GetOption('with_ubsan'):
542        if GetOption('with_asan'):
543            main.Append(CCFLAGS=['-fsanitize=address,undefined',
544                                 '-fno-omit-frame-pointer'],
545                       LINKFLAGS='-fsanitize=address,undefined')
546        else:
547            main.Append(CCFLAGS='-fsanitize=undefined',
548                        LINKFLAGS='-fsanitize=undefined')
549
550    elif GetOption('with_asan'):
551        main.Append(CCFLAGS=['-fsanitize=address',
552                             '-fno-omit-frame-pointer'],
553                   LINKFLAGS='-fsanitize=address')
554
555else:
556    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
557    print("Don't know what compiler options to use for your compiler.")
558    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
559    print(termcap.Yellow + '       version:' + termcap.Normal, end=' ')
560    if not CXX_version:
561        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
562              termcap.Normal)
563    else:
564        print(CXX_version.replace('\n', '<nl>'))
565    print("       If you're trying to use a compiler other than GCC")
566    print("       or clang, there appears to be something wrong with your")
567    print("       environment.")
568    print("       ")
569    print("       If you are trying to use a compiler other than those listed")
570    print("       above you will need to ease fix SConstruct and ")
571    print("       src/SConscript to support that compiler.")
572    Exit(1)
573
574# Set up common yacc/bison flags (needed for Ruby)
575main['YACCFLAGS'] = '-d'
576main['YACCHXXFILESUFFIX'] = '.hh'
577
578# Do this after we save setting back, or else we'll tack on an
579# extra 'qdo' every time we run scons.
580if main['BATCH']:
581    main['CC']     = main['BATCH_CMD'] + ' ' + main['CC']
582    main['CXX']    = main['BATCH_CMD'] + ' ' + main['CXX']
583    main['AS']     = main['BATCH_CMD'] + ' ' + main['AS']
584    main['AR']     = main['BATCH_CMD'] + ' ' + main['AR']
585    main['RANLIB'] = main['BATCH_CMD'] + ' ' + main['RANLIB']
586
587if sys.platform == 'cygwin':
588    # cygwin has some header file issues...
589    main.Append(CCFLAGS=["-Wno-uninitialized"])
590
591# Check for the protobuf compiler
592protoc_version = readCommand([main['PROTOC'], '--version'],
593                             exception='').split()
594
595# First two words should be "libprotoc x.y.z"
596if len(protoc_version) < 2 or protoc_version[0] != 'libprotoc':
597    print(termcap.Yellow + termcap.Bold +
598        'Warning: Protocol buffer compiler (protoc) not found.\n' +
599        '         Please install protobuf-compiler for tracing support.' +
600        termcap.Normal)
601    main['PROTOC'] = False
602else:
603    # Based on the availability of the compress stream wrappers,
604    # require 2.1.0
605    min_protoc_version = '2.1.0'
606    if compareVersions(protoc_version[1], min_protoc_version) < 0:
607        print(termcap.Yellow + termcap.Bold +
608            'Warning: protoc version', min_protoc_version,
609            'or newer required.\n' +
610            '         Installed version:', protoc_version[1],
611            termcap.Normal)
612        main['PROTOC'] = False
613    else:
614        # Attempt to determine the appropriate include path and
615        # library path using pkg-config, that means we also need to
616        # check for pkg-config. Note that it is possible to use
617        # protobuf without the involvement of pkg-config. Later on we
618        # check go a library config check and at that point the test
619        # will fail if libprotobuf cannot be found.
620        if readCommand(['pkg-config', '--version'], exception=''):
621            try:
622                # Attempt to establish what linking flags to add for protobuf
623                # using pkg-config
624                main.ParseConfig('pkg-config --cflags --libs-only-L protobuf')
625            except:
626                print(termcap.Yellow + termcap.Bold +
627                    'Warning: pkg-config could not get protobuf flags.' +
628                    termcap.Normal)
629
630
631# Check for 'timeout' from GNU coreutils. If present, regressions will
632# be run with a time limit. We require version 8.13 since we rely on
633# support for the '--foreground' option.
634if sys.platform.startswith('freebsd'):
635    timeout_lines = readCommand(['gtimeout', '--version'],
636                                exception='').splitlines()
637else:
638    timeout_lines = readCommand(['timeout', '--version'],
639                                exception='').splitlines()
640# Get the first line and tokenize it
641timeout_version = timeout_lines[0].split() if timeout_lines else []
642main['TIMEOUT'] =  timeout_version and \
643    compareVersions(timeout_version[-1], '8.13') >= 0
644
645# Add a custom Check function to test for structure members.
646def CheckMember(context, include, decl, member, include_quotes="<>"):
647    context.Message("Checking for member %s in %s..." %
648                    (member, decl))
649    text = """
650#include %(header)s
651int main(){
652  %(decl)s test;
653  (void)test.%(member)s;
654  return 0;
655};
656""" % { "header" : include_quotes[0] + include + include_quotes[1],
657        "decl" : decl,
658        "member" : member,
659        }
660
661    ret = context.TryCompile(text, extension=".cc")
662    context.Result(ret)
663    return ret
664
665# Platform-specific configuration.  Note again that we assume that all
666# builds under a given build root run on the same host platform.
667conf = Configure(main,
668                 conf_dir = joinpath(build_root, '.scons_config'),
669                 log_file = joinpath(build_root, 'scons_config.log'),
670                 custom_tests = {
671        'CheckMember' : CheckMember,
672        })
673
674# Check if we should compile a 64 bit binary on Mac OS X/Darwin
675try:
676    import platform
677    uname = platform.uname()
678    if uname[0] == 'Darwin' and compareVersions(uname[2], '9.0.0') >= 0:
679        if int(readCommand('sysctl -n hw.cpu64bit_capable')[0]):
680            main.Append(CCFLAGS=['-arch', 'x86_64'])
681            main.Append(CFLAGS=['-arch', 'x86_64'])
682            main.Append(LINKFLAGS=['-arch', 'x86_64'])
683            main.Append(ASFLAGS=['-arch', 'x86_64'])
684except:
685    pass
686
687# Recent versions of scons substitute a "Null" object for Configure()
688# when configuration isn't necessary, e.g., if the "--help" option is
689# present.  Unfortuantely this Null object always returns false,
690# breaking all our configuration checks.  We replace it with our own
691# more optimistic null object that returns True instead.
692if not conf:
693    def NullCheck(*args, **kwargs):
694        return True
695
696    class NullConf:
697        def __init__(self, env):
698            self.env = env
699        def Finish(self):
700            return self.env
701        def __getattr__(self, mname):
702            return NullCheck
703
704    conf = NullConf(main)
705
706# Cache build files in the supplied directory.
707if main['M5_BUILD_CACHE']:
708    print('Using build cache located at', main['M5_BUILD_CACHE'])
709    CacheDir(main['M5_BUILD_CACHE'])
710
711main['USE_PYTHON'] = not GetOption('without_python')
712if main['USE_PYTHON']:
713    # Find Python include and library directories for embedding the
714    # interpreter. We rely on python-config to resolve the appropriate
715    # includes and linker flags. ParseConfig does not seem to understand
716    # the more exotic linker flags such as -Xlinker and -export-dynamic so
717    # we add them explicitly below. If you want to link in an alternate
718    # version of python, see above for instructions on how to invoke
719    # scons with the appropriate PATH set.
720
721    python_config = find_first_prog(main['PYTHON_CONFIG'])
722    if python_config is None:
723        print("Error: can't find a suitable python-config, tried %s" % \
724              main['PYTHON_CONFIG'])
725        Exit(1)
726
727    print("Info: Using Python config: %s" % (python_config, ))
728    py_includes = readCommand([python_config, '--includes'],
729                              exception='').split()
730    py_includes = filter(lambda s: match(r'.*\/include\/.*',s), py_includes)
731    # Strip the -I from the include folders before adding them to the
732    # CPPPATH
733    py_includes = map(lambda s: s[2:] if s.startswith('-I') else s, py_includes)
734    main.Append(CPPPATH=py_includes)
735
736    # Read the linker flags and split them into libraries and other link
737    # flags. The libraries are added later through the call the CheckLib.
738    py_ld_flags = readCommand([python_config, '--ldflags'],
739        exception='').split()
740    py_libs = []
741    for lib in py_ld_flags:
742         if not lib.startswith('-l'):
743             main.Append(LINKFLAGS=[lib])
744         else:
745             lib = lib[2:]
746             if lib not in py_libs:
747                 py_libs.append(lib)
748
749    # verify that this stuff works
750    if not conf.CheckHeader('Python.h', '<>'):
751        print("Error: Check failed for Python.h header in", py_includes)
752        print("Two possible reasons:")
753        print("1. Python headers are not installed (You can install the "
754              "package python-dev on Ubuntu and RedHat)")
755        print("2. SCons is using a wrong C compiler. This can happen if "
756              "CC has the wrong value.")
757        print("CC = %s" % main['CC'])
758        Exit(1)
759
760    for lib in py_libs:
761        if not conf.CheckLib(lib):
762            print("Error: can't find library %s required by python" % lib)
763            Exit(1)
764
765# On Solaris you need to use libsocket for socket ops
766if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
767   if not conf.CheckLibWithHeader('socket', 'sys/socket.h', 'C++', 'accept(0,0,0);'):
768       print("Can't find library with socket calls (e.g. accept())")
769       Exit(1)
770
771# Check for zlib.  If the check passes, libz will be automatically
772# added to the LIBS environment variable.
773if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
774    print('Error: did not find needed zlib compression library '
775          'and/or zlib.h header file.')
776    print('       Please install zlib and try again.')
777    Exit(1)
778
779# If we have the protobuf compiler, also make sure we have the
780# development libraries. If the check passes, libprotobuf will be
781# automatically added to the LIBS environment variable. After
782# this, we can use the HAVE_PROTOBUF flag to determine if we have
783# got both protoc and libprotobuf available.
784main['HAVE_PROTOBUF'] = main['PROTOC'] and \
785    conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
786                            'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
787
788# Valgrind gets much less confused if you tell it when you're using
789# alternative stacks.
790main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
791
792# If we have the compiler but not the library, print another warning.
793if main['PROTOC'] and not main['HAVE_PROTOBUF']:
794    print(termcap.Yellow + termcap.Bold +
795        'Warning: did not find protocol buffer library and/or headers.\n' +
796    '       Please install libprotobuf-dev for tracing support.' +
797    termcap.Normal)
798
799# Check for librt.
800have_posix_clock = \
801    conf.CheckLibWithHeader(None, 'time.h', 'C',
802                            'clock_nanosleep(0,0,NULL,NULL);') or \
803    conf.CheckLibWithHeader('rt', 'time.h', 'C',
804                            'clock_nanosleep(0,0,NULL,NULL);')
805
806have_posix_timers = \
807    conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
808                            'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
809
810if not GetOption('without_tcmalloc'):
811    if conf.CheckLib('tcmalloc'):
812        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
813    elif conf.CheckLib('tcmalloc_minimal'):
814        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
815    else:
816        print(termcap.Yellow + termcap.Bold +
817              "You can get a 12% performance improvement by "
818              "installing tcmalloc (libgoogle-perftools-dev package "
819              "on Ubuntu or RedHat)." + termcap.Normal)
820
821
822# Detect back trace implementations. The last implementation in the
823# list will be used by default.
824backtrace_impls = [ "none" ]
825
826backtrace_checker = 'char temp;' + \
827    ' backtrace_symbols_fd((void*)&temp, 0, 0);'
828if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
829    backtrace_impls.append("glibc")
830elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
831                             backtrace_checker):
832    # NetBSD and FreeBSD need libexecinfo.
833    backtrace_impls.append("glibc")
834    main.Append(LIBS=['execinfo'])
835
836if backtrace_impls[-1] == "none":
837    default_backtrace_impl = "none"
838    print(termcap.Yellow + termcap.Bold +
839        "No suitable back trace implementation found." +
840        termcap.Normal)
841
842if not have_posix_clock:
843    print("Can't find library for POSIX clocks.")
844
845# Check for <fenv.h> (C99 FP environment control)
846have_fenv = conf.CheckHeader('fenv.h', '<>')
847if not have_fenv:
848    print("Warning: Header file <fenv.h> not found.")
849    print("         This host has no IEEE FP rounding mode control.")
850
851# Check for <png.h> (libpng library needed if wanting to dump
852# frame buffer image in png format)
853have_png = conf.CheckHeader('png.h', '<>')
854if not have_png:
855    print("Warning: Header file <png.h> not found.")
856    print("         This host has no libpng library.")
857    print("         Disabling support for PNG framebuffers.")
858
859# Check if we should enable KVM-based hardware virtualization. The API
860# we rely on exists since version 2.6.36 of the kernel, but somehow
861# the KVM_API_VERSION does not reflect the change. We test for one of
862# the types as a fall back.
863have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
864if not have_kvm:
865    print("Info: Compatible header file <linux/kvm.h> not found, "
866          "disabling KVM support.")
867
868# Check if the TUN/TAP driver is available.
869have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
870if not have_tuntap:
871    print("Info: Compatible header file <linux/if_tun.h> not found.")
872
873# x86 needs support for xsave. We test for the structure here since we
874# won't be able to run new tests by the time we know which ISA we're
875# targeting.
876have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
877                                    '#include <linux/kvm.h>') != 0
878
879# Check if the requested target ISA is compatible with the host
880def is_isa_kvm_compatible(isa):
881    try:
882        import platform
883        host_isa = platform.machine()
884    except:
885        print("Warning: Failed to determine host ISA.")
886        return False
887
888    if not have_posix_timers:
889        print("Warning: Can not enable KVM, host seems to lack support "
890              "for POSIX timers")
891        return False
892
893    if isa == "arm":
894        return host_isa in ( "armv7l", "aarch64" )
895    elif isa == "x86":
896        if host_isa != "x86_64":
897            return False
898
899        if not have_kvm_xsave:
900            print("KVM on x86 requires xsave support in kernel headers.")
901            return False
902
903        return True
904    else:
905        return False
906
907
908# Check if the exclude_host attribute is available. We want this to
909# get accurate instruction counts in KVM.
910main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
911    'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
912
913
914######################################################################
915#
916# Finish the configuration
917#
918main = conf.Finish()
919
920######################################################################
921#
922# Collect all non-global variables
923#
924
925# Define the universe of supported ISAs
926all_isa_list = [ ]
927all_gpu_isa_list = [ ]
928Export('all_isa_list')
929Export('all_gpu_isa_list')
930
931class CpuModel(object):
932    '''The CpuModel class encapsulates everything the ISA parser needs to
933    know about a particular CPU model.'''
934
935    # Dict of available CPU model objects.  Accessible as CpuModel.dict.
936    dict = {}
937
938    # Constructor.  Automatically adds models to CpuModel.dict.
939    def __init__(self, name, default=False):
940        self.name = name           # name of model
941
942        # This cpu is enabled by default
943        self.default = default
944
945        # Add self to dict
946        if name in CpuModel.dict:
947            raise AttributeError, "CpuModel '%s' already registered" % name
948        CpuModel.dict[name] = self
949
950Export('CpuModel')
951
952# Sticky variables get saved in the variables file so they persist from
953# one invocation to the next (unless overridden, in which case the new
954# value becomes sticky).
955sticky_vars = Variables(args=ARGUMENTS)
956Export('sticky_vars')
957
958# Sticky variables that should be exported
959export_vars = []
960Export('export_vars')
961
962# For Ruby
963all_protocols = []
964Export('all_protocols')
965protocol_dirs = []
966Export('protocol_dirs')
967slicc_includes = []
968Export('slicc_includes')
969
970# Walk the tree and execute all SConsopts scripts that wil add to the
971# above variables
972if GetOption('verbose'):
973    print("Reading SConsopts")
974for bdir in [ base_dir ] + extras_dir_list:
975    if not isdir(bdir):
976        print("Error: directory '%s' does not exist" % bdir)
977        Exit(1)
978    for root, dirs, files in os.walk(bdir):
979        if 'SConsopts' in files:
980            if GetOption('verbose'):
981                print("Reading", joinpath(root, 'SConsopts'))
982            SConscript(joinpath(root, 'SConsopts'))
983
984all_isa_list.sort()
985all_gpu_isa_list.sort()
986
987sticky_vars.AddVariables(
988    EnumVariable('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
989    EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'hsail', all_gpu_isa_list),
990    ListVariable('CPU_MODELS', 'CPU models',
991                 sorted(n for n,m in CpuModel.dict.iteritems() if m.default),
992                 sorted(CpuModel.dict.keys())),
993    BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
994                 False),
995    BoolVariable('SS_COMPATIBLE_FP',
996                 'Make floating-point results compatible with SimpleScalar',
997                 False),
998    BoolVariable('USE_SSE2',
999                 'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
1000                 False),
1001    BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
1002    BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
1003    BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
1004    BoolVariable('CP_ANNOTATE', 'Enable critical path annotation capability',
1005                 False),
1006    BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
1007                 have_kvm),
1008    BoolVariable('USE_TUNTAP',
1009                 'Enable using a tap device to bridge to the host network',
1010                 have_tuntap),
1011    BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
1012    EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
1013                  all_protocols),
1014    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
1015                 backtrace_impls[-1], backtrace_impls)
1016    )
1017
1018# These variables get exported to #defines in config/*.hh (see src/SConscript).
1019export_vars += ['USE_FENV', 'SS_COMPATIBLE_FP', 'TARGET_ISA', 'TARGET_GPU_ISA',
1020                'CP_ANNOTATE', 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP',
1021                'PROTOCOL', 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
1022                'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG']
1023
1024###################################################
1025#
1026# Define a SCons builder for configuration flag headers.
1027#
1028###################################################
1029
1030# This function generates a config header file that #defines the
1031# variable symbol to the current variable setting (0 or 1).  The source
1032# operands are the name of the variable and a Value node containing the
1033# value of the variable.
1034def build_config_file(target, source, env):
1035    (variable, value) = [s.get_contents() for s in source]
1036    f = file(str(target[0]), 'w')
1037    print('#define', variable, value, file=f)
1038    f.close()
1039    return None
1040
1041# Combine the two functions into a scons Action object.
1042config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1043
1044# The emitter munges the source & target node lists to reflect what
1045# we're really doing.
1046def config_emitter(target, source, env):
1047    # extract variable name from Builder arg
1048    variable = str(target[0])
1049    # True target is config header file
1050    target = joinpath('config', variable.lower() + '.hh')
1051    val = env[variable]
1052    if isinstance(val, bool):
1053        # Force value to 0/1
1054        val = int(val)
1055    elif isinstance(val, str):
1056        val = '"' + val + '"'
1057
1058    # Sources are variable name & value (packaged in SCons Value nodes)
1059    return ([target], [Value(variable), Value(val)])
1060
1061config_builder = Builder(emitter = config_emitter, action = config_action)
1062
1063main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1064
1065###################################################
1066#
1067# Builders for static and shared partially linked object files.
1068#
1069###################################################
1070
1071partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1072                                 src_suffix='$OBJSUFFIX',
1073                                 src_builder=['StaticObject', 'Object'],
1074                                 LINKFLAGS='$PLINKFLAGS',
1075                                 LIBS='')
1076
1077def partial_shared_emitter(target, source, env):
1078    for tgt in target:
1079        tgt.attributes.shared = 1
1080    return (target, source)
1081partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1082                                 emitter=partial_shared_emitter,
1083                                 src_suffix='$SHOBJSUFFIX',
1084                                 src_builder='SharedObject',
1085                                 SHLINKFLAGS='$PSHLINKFLAGS',
1086                                 LIBS='')
1087
1088main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1089                         'PartialStatic' : partial_static_builder })
1090
1091def add_local_rpath(env, *targets):
1092    '''Set up an RPATH for a library which lives in the build directory.
1093
1094    The construction environment variable BIN_RPATH_PREFIX should be set to
1095    the relative path of the build directory starting from the location of the
1096    binary.'''
1097    for target in targets:
1098        target = env.Entry(target)
1099        if not target.isdir():
1100            target = target.dir
1101        relpath = os.path.relpath(target.abspath, env['BUILDDIR'])
1102        components = [
1103            '\\$$ORIGIN',
1104            '${BIN_RPATH_PREFIX}',
1105            relpath
1106        ]
1107        env.Append(RPATH=[env.Literal(os.path.join(*components))])
1108
1109if sys.platform != "darwin":
1110    main.Append(LINKFLAGS=Split('-z origin'))
1111
1112main.AddMethod(add_local_rpath, 'AddLocalRPATH')
1113
1114# builds in ext are shared across all configs in the build root.
1115ext_dir = abspath(joinpath(str(main.root), 'ext'))
1116ext_build_dirs = []
1117for root, dirs, files in os.walk(ext_dir):
1118    if 'SConscript' in files:
1119        build_dir = os.path.relpath(root, ext_dir)
1120        ext_build_dirs.append(build_dir)
1121        main.SConscript(joinpath(root, 'SConscript'),
1122                        variant_dir=joinpath(build_root, build_dir))
1123
1124gdb_xml_dir = joinpath(ext_dir, 'gdb-xml')
1125Export('gdb_xml_dir')
1126
1127main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
1128
1129###################################################
1130#
1131# This builder and wrapper method are used to set up a directory with
1132# switching headers. Those are headers which are in a generic location and
1133# that include more specific headers from a directory chosen at build time
1134# based on the current build settings.
1135#
1136###################################################
1137
1138def build_switching_header(target, source, env):
1139    path = str(target[0])
1140    subdir = str(source[0])
1141    dp, fp = os.path.split(path)
1142    dp = os.path.relpath(os.path.realpath(dp),
1143                         os.path.realpath(env['BUILDDIR']))
1144    with open(path, 'w') as hdr:
1145        print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1146
1147switching_header_action = MakeAction(build_switching_header,
1148                                     Transform('GENERATE'))
1149
1150switching_header_builder = Builder(action=switching_header_action,
1151                                   source_factory=Value,
1152                                   single_source=True)
1153
1154main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1155
1156def switching_headers(self, headers, source):
1157    for header in headers:
1158        self.SwitchingHeader(header, source)
1159
1160main.AddMethod(switching_headers, 'SwitchingHeaders')
1161
1162###################################################
1163#
1164# Define build environments for selected configurations.
1165#
1166###################################################
1167
1168for variant_path in variant_paths:
1169    if not GetOption('silent'):
1170        print("Building in", variant_path)
1171
1172    # Make a copy of the build-root environment to use for this config.
1173    env = main.Clone()
1174    env['BUILDDIR'] = variant_path
1175
1176    # variant_dir is the tail component of build path, and is used to
1177    # determine the build parameters (e.g., 'ALPHA_SE')
1178    (build_root, variant_dir) = splitpath(variant_path)
1179
1180    # Set env variables according to the build directory config.
1181    sticky_vars.files = []
1182    # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1183    # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1184    # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1185    current_vars_file = joinpath(build_root, 'variables', variant_dir)
1186    if isfile(current_vars_file):
1187        sticky_vars.files.append(current_vars_file)
1188        if not GetOption('silent'):
1189            print("Using saved variables file %s" % current_vars_file)
1190    elif variant_dir in ext_build_dirs:
1191        # Things in ext are built without a variant directory.
1192        continue
1193    else:
1194        # Build dir-specific variables file doesn't exist.
1195
1196        # Make sure the directory is there so we can create it later
1197        opt_dir = dirname(current_vars_file)
1198        if not isdir(opt_dir):
1199            mkdir(opt_dir)
1200
1201        # Get default build variables from source tree.  Variables are
1202        # normally determined by name of $VARIANT_DIR, but can be
1203        # overridden by '--default=' arg on command line.
1204        default = GetOption('default')
1205        opts_dir = joinpath(main.root.abspath, 'build_opts')
1206        if default:
1207            default_vars_files = [joinpath(build_root, 'variables', default),
1208                                  joinpath(opts_dir, default)]
1209        else:
1210            default_vars_files = [joinpath(opts_dir, variant_dir)]
1211        existing_files = filter(isfile, default_vars_files)
1212        if existing_files:
1213            default_vars_file = existing_files[0]
1214            sticky_vars.files.append(default_vars_file)
1215            print("Variables file %s not found,\n  using defaults in %s"
1216                  % (current_vars_file, default_vars_file))
1217        else:
1218            print("Error: cannot find variables file %s or "
1219                  "default file(s) %s"
1220                  % (current_vars_file, ' or '.join(default_vars_files)))
1221            Exit(1)
1222
1223    # Apply current variable settings to env
1224    sticky_vars.Update(env)
1225
1226    help_texts["local_vars"] += \
1227        "Build variables for %s:\n" % variant_dir \
1228                 + sticky_vars.GenerateHelpText(env)
1229
1230    # Process variable settings.
1231
1232    if not have_fenv and env['USE_FENV']:
1233        print("Warning: <fenv.h> not available; "
1234              "forcing USE_FENV to False in", variant_dir + ".")
1235        env['USE_FENV'] = False
1236
1237    if not env['USE_FENV']:
1238        print("Warning: No IEEE FP rounding mode control in",
1239              variant_dir + ".")
1240        print("         FP results may deviate slightly from other platforms.")
1241
1242    if not have_png and env['USE_PNG']:
1243        print("Warning: <png.h> not available; "
1244              "forcing USE_PNG to False in", variant_dir + ".")
1245        env['USE_PNG'] = False
1246
1247    if env['USE_PNG']:
1248        env.Append(LIBS=['png'])
1249
1250    if env['EFENCE']:
1251        env.Append(LIBS=['efence'])
1252
1253    if env['USE_KVM']:
1254        if not have_kvm:
1255            print("Warning: Can not enable KVM, host seems to "
1256                  "lack KVM support")
1257            env['USE_KVM'] = False
1258        elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1259            print("Info: KVM support disabled due to unsupported host and "
1260                  "target ISA combination")
1261            env['USE_KVM'] = False
1262
1263    if env['USE_TUNTAP']:
1264        if not have_tuntap:
1265            print("Warning: Can't connect EtherTap with a tap device.")
1266            env['USE_TUNTAP'] = False
1267
1268    if env['BUILD_GPU']:
1269        env.Append(CPPDEFINES=['BUILD_GPU'])
1270
1271    # Warn about missing optional functionality
1272    if env['USE_KVM']:
1273        if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1274            print("Warning: perf_event headers lack support for the "
1275                  "exclude_host attribute. KVM instruction counts will "
1276                  "be inaccurate.")
1277
1278    # Save sticky variable settings back to current variables file
1279    sticky_vars.Save(current_vars_file, env)
1280
1281    if env['USE_SSE2']:
1282        env.Append(CCFLAGS=['-msse2'])
1283
1284    # The src/SConscript file sets up the build rules in 'env' according
1285    # to the configured variables.  It returns a list of environments,
1286    # one for each variant build (debug, opt, etc.)
1287    SConscript('src/SConscript', variant_dir = variant_path, exports = 'env')
1288
1289# base help text
1290Help('''
1291Usage: scons [scons options] [build variables] [target(s)]
1292
1293Extra scons options:
1294%(options)s
1295
1296Global build variables:
1297%(global_vars)s
1298
1299%(local_vars)s
1300''' % help_texts)
1301