SConstruct revision 13758
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
100import SCons.Node.FS
101
102from m5.util import compareVersions, readCommand
103
104help_texts = {
105    "options" : "",
106    "global_vars" : "",
107    "local_vars" : ""
108}
109
110Export("help_texts")
111
112
113# There's a bug in scons in that (1) by default, the help texts from
114# AddOption() are supposed to be displayed when you type 'scons -h'
115# and (2) you can override the help displayed by 'scons -h' using the
116# Help() function, but these two features are incompatible: once
117# you've overridden the help text using Help(), there's no way to get
118# at the help texts from AddOptions.  See:
119#     http://scons.tigris.org/issues/show_bug.cgi?id=2356
120#     http://scons.tigris.org/issues/show_bug.cgi?id=2611
121# This hack lets us extract the help text from AddOptions and
122# re-inject it via Help().  Ideally someday this bug will be fixed and
123# we can just use AddOption directly.
124def AddLocalOption(*args, **kwargs):
125    col_width = 30
126
127    help = "  " + ", ".join(args)
128    if "help" in kwargs:
129        length = len(help)
130        if length >= col_width:
131            help += "\n" + " " * col_width
132        else:
133            help += " " * (col_width - length)
134        help += kwargs["help"]
135    help_texts["options"] += help + "\n"
136
137    AddOption(*args, **kwargs)
138
139AddLocalOption('--colors', dest='use_colors', action='store_true',
140               help="Add color to abbreviated scons output")
141AddLocalOption('--no-colors', dest='use_colors', action='store_false',
142               help="Don't add color to abbreviated scons output")
143AddLocalOption('--with-cxx-config', dest='with_cxx_config',
144               action='store_true',
145               help="Build with support for C++-based configuration")
146AddLocalOption('--default', dest='default', type='string', action='store',
147               help='Override which build_opts file to use for defaults')
148AddLocalOption('--ignore-style', dest='ignore_style', action='store_true',
149               help='Disable style checking hooks')
150AddLocalOption('--gold-linker', dest='gold_linker', action='store_true',
151               help='Use the gold linker')
152AddLocalOption('--no-lto', dest='no_lto', action='store_true',
153               help='Disable Link-Time Optimization for fast')
154AddLocalOption('--force-lto', dest='force_lto', action='store_true',
155               help='Use Link-Time Optimization instead of partial linking' +
156                    ' when the compiler doesn\'t support using them together.')
157AddLocalOption('--update-ref', dest='update_ref', action='store_true',
158               help='Update test reference outputs')
159AddLocalOption('--verbose', dest='verbose', action='store_true',
160               help='Print full tool command lines')
161AddLocalOption('--without-python', dest='without_python',
162               action='store_true',
163               help='Build without Python configuration support')
164AddLocalOption('--without-tcmalloc', dest='without_tcmalloc',
165               action='store_true',
166               help='Disable linking against tcmalloc')
167AddLocalOption('--with-ubsan', dest='with_ubsan', action='store_true',
168               help='Build with Undefined Behavior Sanitizer if available')
169AddLocalOption('--with-asan', dest='with_asan', action='store_true',
170               help='Build with Address Sanitizer if available')
171
172if GetOption('no_lto') and GetOption('force_lto'):
173    print('--no-lto and --force-lto are mutually exclusive')
174    Exit(1)
175
176########################################################################
177#
178# Set up the main build environment.
179#
180########################################################################
181
182main = Environment()
183
184from gem5_scons import Transform
185from gem5_scons.util import get_termcap
186termcap = get_termcap()
187
188main_dict_keys = main.Dictionary().keys()
189
190# Check that we have a C/C++ compiler
191if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
192    print("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
193    Exit(1)
194
195###################################################
196#
197# Figure out which configurations to set up based on the path(s) of
198# the target(s).
199#
200###################################################
201
202# Find default configuration & binary.
203Default(environ.get('M5_DEFAULT_BINARY', 'build/ALPHA/gem5.debug'))
204
205# helper function: find last occurrence of element in list
206def rfind(l, elt, offs = -1):
207    for i in range(len(l)+offs, 0, -1):
208        if l[i] == elt:
209            return i
210    raise ValueError, "element not found"
211
212# Take a list of paths (or SCons Nodes) and return a list with all
213# paths made absolute and ~-expanded.  Paths will be interpreted
214# relative to the launch directory unless a different root is provided
215def makePathListAbsolute(path_list, root=GetLaunchDir()):
216    return [abspath(joinpath(root, expanduser(str(p))))
217            for p in path_list]
218
219def find_first_prog(prog_names):
220    """Find the absolute path to the first existing binary in prog_names"""
221
222    if not isinstance(prog_names, (list, tuple)):
223        prog_names = [ prog_names ]
224
225    for p in prog_names:
226        p = main.WhereIs(p)
227        if p is not None:
228            return p
229
230    return None
231
232# Each target must have 'build' in the interior of the path; the
233# directory below this will determine the build parameters.  For
234# example, for target 'foo/bar/build/ALPHA_SE/arch/alpha/blah.do' we
235# recognize that ALPHA_SE specifies the configuration because it
236# follow 'build' in the build path.
237
238# The funky assignment to "[:]" is needed to replace the list contents
239# in place rather than reassign the symbol to a new list, which
240# doesn't work (obviously!).
241BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
242
243# Generate a list of the unique build roots and configs that the
244# collected targets reference.
245variant_paths = []
246build_root = None
247for t in BUILD_TARGETS:
248    path_dirs = t.split('/')
249    try:
250        build_top = rfind(path_dirs, 'build', -2)
251    except:
252        print("Error: no non-leaf 'build' dir found on target path", t)
253        Exit(1)
254    this_build_root = joinpath('/',*path_dirs[:build_top+1])
255    if not build_root:
256        build_root = this_build_root
257    else:
258        if this_build_root != build_root:
259            print("Error: build targets not under same build root\n"
260                  "  %s\n  %s" % (build_root, this_build_root))
261            Exit(1)
262    variant_path = joinpath('/',*path_dirs[:build_top+2])
263    if variant_path not in variant_paths:
264        variant_paths.append(variant_path)
265
266# Make sure build_root exists (might not if this is the first build there)
267if not isdir(build_root):
268    mkdir(build_root)
269main['BUILDROOT'] = build_root
270
271Export('main')
272
273main.SConsignFile(joinpath(build_root, "sconsign"))
274
275# Default duplicate option is to use hard links, but this messes up
276# when you use emacs to edit a file in the target dir, as emacs moves
277# file to file~ then copies to file, breaking the link.  Symbolic
278# (soft) links work better.
279main.SetOption('duplicate', 'soft-copy')
280
281#
282# Set up global sticky variables... these are common to an entire build
283# tree (not specific to a particular build like ALPHA_SE)
284#
285
286global_vars_file = joinpath(build_root, 'variables.global')
287
288global_vars = Variables(global_vars_file, args=ARGUMENTS)
289
290global_vars.AddVariables(
291    ('CC', 'C compiler', environ.get('CC', main['CC'])),
292    ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
293    ('PYTHON_CONFIG', 'Python config binary to use',
294     [ 'python2.7-config', 'python-config' ]),
295    ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
296    ('BATCH', 'Use batch pool for build and tests', False),
297    ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
298    ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
299    ('EXTRAS', 'Add extra directories to the compilation', '')
300    )
301
302# Update main environment with values from ARGUMENTS & global_vars_file
303global_vars.Update(main)
304help_texts["global_vars"] += global_vars.GenerateHelpText(main)
305
306# Save sticky variable settings back to current variables file
307global_vars.Save(global_vars_file, main)
308
309# Parse EXTRAS variable to build list of all directories where we're
310# look for sources etc.  This list is exported as extras_dir_list.
311base_dir = main.srcdir.abspath
312if main['EXTRAS']:
313    extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
314else:
315    extras_dir_list = []
316
317Export('base_dir')
318Export('extras_dir_list')
319
320# the ext directory should be on the #includes path
321main.Append(CPPPATH=[Dir('ext')])
322
323# Add shared top-level headers
324main.Prepend(CPPPATH=Dir('include'))
325
326if GetOption('verbose'):
327    def MakeAction(action, string, *args, **kwargs):
328        return Action(action, *args, **kwargs)
329else:
330    MakeAction = Action
331    main['CCCOMSTR']        = Transform("CC")
332    main['CXXCOMSTR']       = Transform("CXX")
333    main['ASCOMSTR']        = Transform("AS")
334    main['ARCOMSTR']        = Transform("AR", 0)
335    main['LINKCOMSTR']      = Transform("LINK", 0)
336    main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
337    main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
338    main['M4COMSTR']        = Transform("M4")
339    main['SHCCCOMSTR']      = Transform("SHCC")
340    main['SHCXXCOMSTR']     = Transform("SHCXX")
341Export('MakeAction')
342
343# Initialize the Link-Time Optimization (LTO) flags
344main['LTO_CCFLAGS'] = []
345main['LTO_LDFLAGS'] = []
346
347# According to the readme, tcmalloc works best if the compiler doesn't
348# assume that we're using the builtin malloc and friends. These flags
349# are compiler-specific, so we need to set them after we detect which
350# compiler we're using.
351main['TCMALLOC_CCFLAGS'] = []
352
353CXX_version = readCommand([main['CXX'],'--version'], exception=False)
354CXX_V = readCommand([main['CXX'],'-V'], exception=False)
355
356main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
357main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
358if main['GCC'] + main['CLANG'] > 1:
359    print('Error: How can we have two at the same time?')
360    Exit(1)
361
362# Set up default C++ compiler flags
363if main['GCC'] or main['CLANG']:
364    # As gcc and clang share many flags, do the common parts here
365    main.Append(CCFLAGS=['-pipe'])
366    main.Append(CCFLAGS=['-fno-strict-aliasing'])
367    # Enable -Wall and -Wextra and then disable the few warnings that
368    # we consistently violate
369    main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
370                         '-Wno-sign-compare', '-Wno-unused-parameter'])
371    # We always compile using C++11
372    main.Append(CXXFLAGS=['-std=c++11'])
373    if sys.platform.startswith('freebsd'):
374        main.Append(CCFLAGS=['-I/usr/local/include'])
375        main.Append(CXXFLAGS=['-I/usr/local/include'])
376
377    main['FILTER_PSHLINKFLAGS'] = lambda x: str(x).replace(' -shared', '')
378    main['PSHLINKFLAGS'] = main.subst('${FILTER_PSHLINKFLAGS(SHLINKFLAGS)}')
379    if GetOption('gold_linker'):
380        main.Append(LINKFLAGS='-fuse-ld=gold')
381    main['PLINKFLAGS'] = main.subst('${LINKFLAGS}')
382    shared_partial_flags = ['-r', '-nostdlib']
383    main.Append(PSHLINKFLAGS=shared_partial_flags)
384    main.Append(PLINKFLAGS=shared_partial_flags)
385
386    # Treat warnings as errors but white list some warnings that we
387    # want to allow (e.g., deprecation warnings).
388    main.Append(CCFLAGS=['-Werror',
389                         '-Wno-error=deprecated-declarations',
390                         '-Wno-error=deprecated',
391                        ])
392else:
393    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
394    print("Don't know what compiler options to use for your compiler.")
395    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
396    print(termcap.Yellow + '       version:' + termcap.Normal, end = ' ')
397    if not CXX_version:
398        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
399              termcap.Normal)
400    else:
401        print(CXX_version.replace('\n', '<nl>'))
402    print("       If you're trying to use a compiler other than GCC")
403    print("       or clang, there appears to be something wrong with your")
404    print("       environment.")
405    print("       ")
406    print("       If you are trying to use a compiler other than those listed")
407    print("       above you will need to ease fix SConstruct and ")
408    print("       src/SConscript to support that compiler.")
409    Exit(1)
410
411if main['GCC']:
412    # Check for a supported version of gcc. >= 4.8 is chosen for its
413    # level of c++11 support. See
414    # http://gcc.gnu.org/projects/cxx0x.html for details.
415    gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
416    if compareVersions(gcc_version, "4.8") < 0:
417        print('Error: gcc version 4.8 or newer required.')
418        print('       Installed version: ', gcc_version)
419        Exit(1)
420
421    main['GCC_VERSION'] = gcc_version
422
423    if compareVersions(gcc_version, '4.9') >= 0:
424        # Incremental linking with LTO is currently broken in gcc versions
425        # 4.9 and above. A version where everything works completely hasn't
426        # yet been identified.
427        #
428        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548
429        main['BROKEN_INCREMENTAL_LTO'] = True
430    if compareVersions(gcc_version, '6.0') >= 0:
431        # gcc versions 6.0 and greater accept an -flinker-output flag which
432        # selects what type of output the linker should generate. This is
433        # necessary for incremental lto to work, but is also broken in
434        # current versions of gcc. It may not be necessary in future
435        # versions. We add it here since it might be, and as a reminder that
436        # it exists. It's excluded if lto is being forced.
437        #
438        # https://gcc.gnu.org/gcc-6/changes.html
439        # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html
440        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866
441        if not GetOption('force_lto'):
442            main.Append(PSHLINKFLAGS='-flinker-output=rel')
443            main.Append(PLINKFLAGS='-flinker-output=rel')
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            main.Append(CCFLAGS=['-fsanitize=address,undefined',
545                                 '-fno-omit-frame-pointer'],
546                       LINKFLAGS='-fsanitize=address,undefined')
547        else:
548            main.Append(CCFLAGS='-fsanitize=undefined',
549                        LINKFLAGS='-fsanitize=undefined')
550
551    elif GetOption('with_asan'):
552        main.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    python_config = find_first_prog(main['PYTHON_CONFIG'])
723    if python_config is None:
724        print("Error: can't find a suitable python-config, tried %s" % \
725              main['PYTHON_CONFIG'])
726        Exit(1)
727
728    print("Info: Using Python config: %s" % (python_config, ))
729    py_includes = readCommand([python_config, '--includes'],
730                              exception='').split()
731    py_includes = filter(lambda s: match(r'.*\/include\/.*',s), py_includes)
732    # Strip the -I from the include folders before adding them to the
733    # CPPPATH
734    py_includes = map(lambda s: s[2:] if s.startswith('-I') else s, py_includes)
735    main.Append(CPPPATH=py_includes)
736
737    # Read the linker flags and split them into libraries and other link
738    # flags. The libraries are added later through the call the CheckLib.
739    py_ld_flags = readCommand([python_config, '--ldflags'],
740        exception='').split()
741    py_libs = []
742    for lib in py_ld_flags:
743         if not lib.startswith('-l'):
744             main.Append(LINKFLAGS=[lib])
745         else:
746             lib = lib[2:]
747             if lib not in py_libs:
748                 py_libs.append(lib)
749
750    # verify that this stuff works
751    if not conf.CheckHeader('Python.h', '<>'):
752        print("Error: Check failed for Python.h header in", py_includes)
753        print("Two possible reasons:")
754        print("1. Python headers are not installed (You can install the "
755              "package python-dev on Ubuntu and RedHat)")
756        print("2. SCons is using a wrong C compiler. This can happen if "
757              "CC has the wrong value.")
758        print("CC = %s" % main['CC'])
759        Exit(1)
760
761    for lib in py_libs:
762        if not conf.CheckLib(lib):
763            print("Error: can't find library %s required by python" % lib)
764            Exit(1)
765
766# On Solaris you need to use libsocket for socket ops
767if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
768   if not conf.CheckLibWithHeader('socket', 'sys/socket.h', 'C++', 'accept(0,0,0);'):
769       print("Can't find library with socket calls (e.g. accept())")
770       Exit(1)
771
772# Check for zlib.  If the check passes, libz will be automatically
773# added to the LIBS environment variable.
774if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
775    print('Error: did not find needed zlib compression library '
776          'and/or zlib.h header file.')
777    print('       Please install zlib and try again.')
778    Exit(1)
779
780# If we have the protobuf compiler, also make sure we have the
781# development libraries. If the check passes, libprotobuf will be
782# automatically added to the LIBS environment variable. After
783# this, we can use the HAVE_PROTOBUF flag to determine if we have
784# got both protoc and libprotobuf available.
785main['HAVE_PROTOBUF'] = main['PROTOC'] and \
786    conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
787                            'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
788
789# Valgrind gets much less confused if you tell it when you're using
790# alternative stacks.
791main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
792
793# If we have the compiler but not the library, print another warning.
794if main['PROTOC'] and not main['HAVE_PROTOBUF']:
795    print(termcap.Yellow + termcap.Bold +
796        'Warning: did not find protocol buffer library and/or headers.\n' +
797    '       Please install libprotobuf-dev for tracing support.' +
798    termcap.Normal)
799
800# Check for librt.
801have_posix_clock = \
802    conf.CheckLibWithHeader(None, 'time.h', 'C',
803                            'clock_nanosleep(0,0,NULL,NULL);') or \
804    conf.CheckLibWithHeader('rt', 'time.h', 'C',
805                            'clock_nanosleep(0,0,NULL,NULL);')
806
807have_posix_timers = \
808    conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
809                            'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
810
811if not GetOption('without_tcmalloc'):
812    if conf.CheckLib('tcmalloc'):
813        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
814    elif conf.CheckLib('tcmalloc_minimal'):
815        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
816    else:
817        print(termcap.Yellow + termcap.Bold +
818              "You can get a 12% performance improvement by "
819              "installing tcmalloc (libgoogle-perftools-dev package "
820              "on Ubuntu or RedHat)." + termcap.Normal)
821
822
823# Detect back trace implementations. The last implementation in the
824# list will be used by default.
825backtrace_impls = [ "none" ]
826
827backtrace_checker = 'char temp;' + \
828    ' backtrace_symbols_fd((void*)&temp, 0, 0);'
829if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
830    backtrace_impls.append("glibc")
831elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
832                             backtrace_checker):
833    # NetBSD and FreeBSD need libexecinfo.
834    backtrace_impls.append("glibc")
835    main.Append(LIBS=['execinfo'])
836
837if backtrace_impls[-1] == "none":
838    default_backtrace_impl = "none"
839    print(termcap.Yellow + termcap.Bold +
840        "No suitable back trace implementation found." +
841        termcap.Normal)
842
843if not have_posix_clock:
844    print("Can't find library for POSIX clocks.")
845
846# Check for <fenv.h> (C99 FP environment control)
847have_fenv = conf.CheckHeader('fenv.h', '<>')
848if not have_fenv:
849    print("Warning: Header file <fenv.h> not found.")
850    print("         This host has no IEEE FP rounding mode control.")
851
852# Check for <png.h> (libpng library needed if wanting to dump
853# frame buffer image in png format)
854have_png = conf.CheckHeader('png.h', '<>')
855if not have_png:
856    print("Warning: Header file <png.h> not found.")
857    print("         This host has no libpng library.")
858    print("         Disabling support for PNG framebuffers.")
859
860# Check if we should enable KVM-based hardware virtualization. The API
861# we rely on exists since version 2.6.36 of the kernel, but somehow
862# the KVM_API_VERSION does not reflect the change. We test for one of
863# the types as a fall back.
864have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
865if not have_kvm:
866    print("Info: Compatible header file <linux/kvm.h> not found, "
867          "disabling KVM support.")
868
869# Check if the TUN/TAP driver is available.
870have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
871if not have_tuntap:
872    print("Info: Compatible header file <linux/if_tun.h> not found.")
873
874# x86 needs support for xsave. We test for the structure here since we
875# won't be able to run new tests by the time we know which ISA we're
876# targeting.
877have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
878                                    '#include <linux/kvm.h>') != 0
879
880# Check if the requested target ISA is compatible with the host
881def is_isa_kvm_compatible(isa):
882    try:
883        import platform
884        host_isa = platform.machine()
885    except:
886        print("Warning: Failed to determine host ISA.")
887        return False
888
889    if not have_posix_timers:
890        print("Warning: Can not enable KVM, host seems to lack support "
891              "for POSIX timers")
892        return False
893
894    if isa == "arm":
895        return host_isa in ( "armv7l", "aarch64" )
896    elif isa == "x86":
897        if host_isa != "x86_64":
898            return False
899
900        if not have_kvm_xsave:
901            print("KVM on x86 requires xsave support in kernel headers.")
902            return False
903
904        return True
905    else:
906        return False
907
908
909# Check if the exclude_host attribute is available. We want this to
910# get accurate instruction counts in KVM.
911main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
912    'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
913
914
915######################################################################
916#
917# Finish the configuration
918#
919main = conf.Finish()
920
921######################################################################
922#
923# Collect all non-global variables
924#
925
926# Define the universe of supported ISAs
927all_isa_list = [ ]
928all_gpu_isa_list = [ ]
929Export('all_isa_list')
930Export('all_gpu_isa_list')
931
932class CpuModel(object):
933    '''The CpuModel class encapsulates everything the ISA parser needs to
934    know about a particular CPU model.'''
935
936    # Dict of available CPU model objects.  Accessible as CpuModel.dict.
937    dict = {}
938
939    # Constructor.  Automatically adds models to CpuModel.dict.
940    def __init__(self, name, default=False):
941        self.name = name           # name of model
942
943        # This cpu is enabled by default
944        self.default = default
945
946        # Add self to dict
947        if name in CpuModel.dict:
948            raise AttributeError, "CpuModel '%s' already registered" % name
949        CpuModel.dict[name] = self
950
951Export('CpuModel')
952
953# Sticky variables get saved in the variables file so they persist from
954# one invocation to the next (unless overridden, in which case the new
955# value becomes sticky).
956sticky_vars = Variables(args=ARGUMENTS)
957Export('sticky_vars')
958
959# Sticky variables that should be exported
960export_vars = []
961Export('export_vars')
962
963# For Ruby
964all_protocols = []
965Export('all_protocols')
966protocol_dirs = []
967Export('protocol_dirs')
968slicc_includes = []
969Export('slicc_includes')
970
971# Walk the tree and execute all SConsopts scripts that wil add to the
972# above variables
973if GetOption('verbose'):
974    print("Reading SConsopts")
975for bdir in [ base_dir ] + extras_dir_list:
976    if not isdir(bdir):
977        print("Error: directory '%s' does not exist" % bdir)
978        Exit(1)
979    for root, dirs, files in os.walk(bdir):
980        if 'SConsopts' in files:
981            if GetOption('verbose'):
982                print("Reading", joinpath(root, 'SConsopts'))
983            SConscript(joinpath(root, 'SConsopts'))
984
985all_isa_list.sort()
986all_gpu_isa_list.sort()
987
988sticky_vars.AddVariables(
989    EnumVariable('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
990    EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'hsail', all_gpu_isa_list),
991    ListVariable('CPU_MODELS', 'CPU models',
992                 sorted(n for n,m in CpuModel.dict.iteritems() if m.default),
993                 sorted(CpuModel.dict.keys())),
994    BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
995                 False),
996    BoolVariable('SS_COMPATIBLE_FP',
997                 'Make floating-point results compatible with SimpleScalar',
998                 False),
999    BoolVariable('USE_SSE2',
1000                 'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
1001                 False),
1002    BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
1003    BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
1004    BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
1005    BoolVariable('CP_ANNOTATE', 'Enable critical path annotation capability',
1006                 False),
1007    BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
1008                 have_kvm),
1009    BoolVariable('USE_TUNTAP',
1010                 'Enable using a tap device to bridge to the host network',
1011                 have_tuntap),
1012    BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
1013    EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
1014                  all_protocols),
1015    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
1016                 backtrace_impls[-1], backtrace_impls)
1017    )
1018
1019# These variables get exported to #defines in config/*.hh (see src/SConscript).
1020export_vars += ['USE_FENV', 'SS_COMPATIBLE_FP', 'TARGET_ISA', 'TARGET_GPU_ISA',
1021                'CP_ANNOTATE', 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP',
1022                'PROTOCOL', 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
1023                'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG']
1024
1025###################################################
1026#
1027# Define a SCons builder for configuration flag headers.
1028#
1029###################################################
1030
1031# This function generates a config header file that #defines the
1032# variable symbol to the current variable setting (0 or 1).  The source
1033# operands are the name of the variable and a Value node containing the
1034# value of the variable.
1035def build_config_file(target, source, env):
1036    (variable, value) = [s.get_contents() for s in source]
1037    f = file(str(target[0]), 'w')
1038    print('#define', variable, value, file=f)
1039    f.close()
1040    return None
1041
1042# Combine the two functions into a scons Action object.
1043config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1044
1045# The emitter munges the source & target node lists to reflect what
1046# we're really doing.
1047def config_emitter(target, source, env):
1048    # extract variable name from Builder arg
1049    variable = str(target[0])
1050    # True target is config header file
1051    target = joinpath('config', variable.lower() + '.hh')
1052    val = env[variable]
1053    if isinstance(val, bool):
1054        # Force value to 0/1
1055        val = int(val)
1056    elif isinstance(val, str):
1057        val = '"' + val + '"'
1058
1059    # Sources are variable name & value (packaged in SCons Value nodes)
1060    return ([target], [Value(variable), Value(val)])
1061
1062config_builder = Builder(emitter = config_emitter, action = config_action)
1063
1064main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1065
1066###################################################
1067#
1068# Builders for static and shared partially linked object files.
1069#
1070###################################################
1071
1072partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1073                                 src_suffix='$OBJSUFFIX',
1074                                 src_builder=['StaticObject', 'Object'],
1075                                 LINKFLAGS='$PLINKFLAGS',
1076                                 LIBS='')
1077
1078def partial_shared_emitter(target, source, env):
1079    for tgt in target:
1080        tgt.attributes.shared = 1
1081    return (target, source)
1082partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1083                                 emitter=partial_shared_emitter,
1084                                 src_suffix='$SHOBJSUFFIX',
1085                                 src_builder='SharedObject',
1086                                 SHLINKFLAGS='$PSHLINKFLAGS',
1087                                 LIBS='')
1088
1089main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1090                         'PartialStatic' : partial_static_builder })
1091
1092def add_local_rpath(env, *targets):
1093    '''Set up an RPATH for a library which lives in the build directory.
1094
1095    The construction environment variable BIN_RPATH_PREFIX should be set to
1096    the relative path of the build directory starting from the location of the
1097    binary.'''
1098    for target in targets:
1099        target = env.Entry(target)
1100        if not isinstance(target, SCons.Node.FS.Dir):
1101            target = target.dir
1102        relpath = os.path.relpath(target.abspath, env['BUILDDIR'])
1103        components = [
1104            '\\$$ORIGIN',
1105            '${BIN_RPATH_PREFIX}',
1106            relpath
1107        ]
1108        env.Append(RPATH=[env.Literal(os.path.join(*components))])
1109
1110if sys.platform != "darwin":
1111    main.Append(LINKFLAGS=Split('-z origin'))
1112
1113main.AddMethod(add_local_rpath, 'AddLocalRPATH')
1114
1115# builds in ext are shared across all configs in the build root.
1116ext_dir = abspath(joinpath(str(main.root), 'ext'))
1117ext_build_dirs = []
1118for root, dirs, files in os.walk(ext_dir):
1119    if 'SConscript' in files:
1120        build_dir = os.path.relpath(root, ext_dir)
1121        ext_build_dirs.append(build_dir)
1122        main.SConscript(joinpath(root, 'SConscript'),
1123                        variant_dir=joinpath(build_root, build_dir))
1124
1125gdb_xml_dir = joinpath(ext_dir, 'gdb-xml')
1126Export('gdb_xml_dir')
1127
1128main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
1129
1130###################################################
1131#
1132# This builder and wrapper method are used to set up a directory with
1133# switching headers. Those are headers which are in a generic location and
1134# that include more specific headers from a directory chosen at build time
1135# based on the current build settings.
1136#
1137###################################################
1138
1139def build_switching_header(target, source, env):
1140    path = str(target[0])
1141    subdir = str(source[0])
1142    dp, fp = os.path.split(path)
1143    dp = os.path.relpath(os.path.realpath(dp),
1144                         os.path.realpath(env['BUILDDIR']))
1145    with open(path, 'w') as hdr:
1146        print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1147
1148switching_header_action = MakeAction(build_switching_header,
1149                                     Transform('GENERATE'))
1150
1151switching_header_builder = Builder(action=switching_header_action,
1152                                   source_factory=Value,
1153                                   single_source=True)
1154
1155main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1156
1157def switching_headers(self, headers, source):
1158    for header in headers:
1159        self.SwitchingHeader(header, source)
1160
1161main.AddMethod(switching_headers, 'SwitchingHeaders')
1162
1163###################################################
1164#
1165# Define build environments for selected configurations.
1166#
1167###################################################
1168
1169for variant_path in variant_paths:
1170    if not GetOption('silent'):
1171        print("Building in", variant_path)
1172
1173    # Make a copy of the build-root environment to use for this config.
1174    env = main.Clone()
1175    env['BUILDDIR'] = variant_path
1176
1177    # variant_dir is the tail component of build path, and is used to
1178    # determine the build parameters (e.g., 'ALPHA_SE')
1179    (build_root, variant_dir) = splitpath(variant_path)
1180
1181    # Set env variables according to the build directory config.
1182    sticky_vars.files = []
1183    # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1184    # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1185    # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1186    current_vars_file = joinpath(build_root, 'variables', variant_dir)
1187    if isfile(current_vars_file):
1188        sticky_vars.files.append(current_vars_file)
1189        if not GetOption('silent'):
1190            print("Using saved variables file %s" % current_vars_file)
1191    elif variant_dir in ext_build_dirs:
1192        # Things in ext are built without a variant directory.
1193        continue
1194    else:
1195        # Build dir-specific variables file doesn't exist.
1196
1197        # Make sure the directory is there so we can create it later
1198        opt_dir = dirname(current_vars_file)
1199        if not isdir(opt_dir):
1200            mkdir(opt_dir)
1201
1202        # Get default build variables from source tree.  Variables are
1203        # normally determined by name of $VARIANT_DIR, but can be
1204        # overridden by '--default=' arg on command line.
1205        default = GetOption('default')
1206        opts_dir = joinpath(main.root.abspath, 'build_opts')
1207        if default:
1208            default_vars_files = [joinpath(build_root, 'variables', default),
1209                                  joinpath(opts_dir, default)]
1210        else:
1211            default_vars_files = [joinpath(opts_dir, variant_dir)]
1212        existing_files = filter(isfile, default_vars_files)
1213        if existing_files:
1214            default_vars_file = existing_files[0]
1215            sticky_vars.files.append(default_vars_file)
1216            print("Variables file %s not found,\n  using defaults in %s"
1217                  % (current_vars_file, default_vars_file))
1218        else:
1219            print("Error: cannot find variables file %s or "
1220                  "default file(s) %s"
1221                  % (current_vars_file, ' or '.join(default_vars_files)))
1222            Exit(1)
1223
1224    # Apply current variable settings to env
1225    sticky_vars.Update(env)
1226
1227    help_texts["local_vars"] += \
1228        "Build variables for %s:\n" % variant_dir \
1229                 + sticky_vars.GenerateHelpText(env)
1230
1231    # Process variable settings.
1232
1233    if not have_fenv and env['USE_FENV']:
1234        print("Warning: <fenv.h> not available; "
1235              "forcing USE_FENV to False in", variant_dir + ".")
1236        env['USE_FENV'] = False
1237
1238    if not env['USE_FENV']:
1239        print("Warning: No IEEE FP rounding mode control in",
1240              variant_dir + ".")
1241        print("         FP results may deviate slightly from other platforms.")
1242
1243    if not have_png and env['USE_PNG']:
1244        print("Warning: <png.h> not available; "
1245              "forcing USE_PNG to False in", variant_dir + ".")
1246        env['USE_PNG'] = False
1247
1248    if env['USE_PNG']:
1249        env.Append(LIBS=['png'])
1250
1251    if env['EFENCE']:
1252        env.Append(LIBS=['efence'])
1253
1254    if env['USE_KVM']:
1255        if not have_kvm:
1256            print("Warning: Can not enable KVM, host seems to "
1257                  "lack KVM support")
1258            env['USE_KVM'] = False
1259        elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1260            print("Info: KVM support disabled due to unsupported host and "
1261                  "target ISA combination")
1262            env['USE_KVM'] = False
1263
1264    if env['USE_TUNTAP']:
1265        if not have_tuntap:
1266            print("Warning: Can't connect EtherTap with a tap device.")
1267            env['USE_TUNTAP'] = False
1268
1269    if env['BUILD_GPU']:
1270        env.Append(CPPDEFINES=['BUILD_GPU'])
1271
1272    # Warn about missing optional functionality
1273    if env['USE_KVM']:
1274        if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1275            print("Warning: perf_event headers lack support for the "
1276                  "exclude_host attribute. KVM instruction counts will "
1277                  "be inaccurate.")
1278
1279    # Save sticky variable settings back to current variables file
1280    sticky_vars.Save(current_vars_file, env)
1281
1282    if env['USE_SSE2']:
1283        env.Append(CCFLAGS=['-msse2'])
1284
1285    # The src/SConscript file sets up the build rules in 'env' according
1286    # to the configured variables.  It returns a list of environments,
1287    # one for each variant build (debug, opt, etc.)
1288    SConscript('src/SConscript', variant_dir = variant_path, exports = 'env')
1289
1290# base help text
1291Help('''
1292Usage: scons [scons options] [build variables] [target(s)]
1293
1294Extra scons options:
1295%(options)s
1296
1297Global build variables:
1298%(global_vars)s
1299
1300%(local_vars)s
1301''' % help_texts)
1302