SConstruct revision 13421
1# -*- mode:python -*-
2
3# Copyright (c) 2013, 2015-2017 ARM Limited
4# All rights reserved.
5#
6# The license below extends only to copyright in the software and shall
7# not be construed as granting a license to any other intellectual
8# property including but not limited to intellectual property relating
9# to a hardware implementation of the functionality of the software
10# licensed hereunder.  You may use the software subject to the license
11# terms below provided that you ensure that this notice is replicated
12# unmodified and in its entirety in all distributions of the software,
13# modified or unmodified, in source code or in binary form.
14#
15# Copyright (c) 2011 Advanced Micro Devices, Inc.
16# Copyright (c) 2009 The Hewlett-Packard Development Company
17# Copyright (c) 2004-2005 The Regents of The University of Michigan
18# All rights reserved.
19#
20# Redistribution and use in source and binary forms, with or without
21# modification, are permitted provided that the following conditions are
22# met: redistributions of source code must retain the above copyright
23# notice, this list of conditions and the following disclaimer;
24# redistributions in binary form must reproduce the above copyright
25# notice, this list of conditions and the following disclaimer in the
26# documentation and/or other materials provided with the distribution;
27# neither the name of the copyright holders nor the names of its
28# contributors may be used to endorse or promote products derived from
29# this software without specific prior written permission.
30#
31# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
34# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
36# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
37# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
41# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42#
43# Authors: Steve Reinhardt
44#          Nathan Binkert
45
46###################################################
47#
48# SCons top-level build description (SConstruct) file.
49#
50# While in this directory ('gem5'), just type 'scons' to build the default
51# configuration (see below), or type 'scons build/<CONFIG>/<binary>'
52# to build some other configuration (e.g., 'build/ALPHA/gem5.opt' for
53# the optimized full-system version).
54#
55# You can build gem5 in a different directory as long as there is a
56# 'build/<CONFIG>' somewhere along the target path.  The build system
57# expects that all configs under the same build directory are being
58# built for the same host system.
59#
60# Examples:
61#
62#   The following two commands are equivalent.  The '-u' option tells
63#   scons to search up the directory tree for this SConstruct file.
64#   % cd <path-to-src>/gem5 ; scons build/ALPHA/gem5.debug
65#   % cd <path-to-src>/gem5/build/ALPHA; scons -u gem5.debug
66#
67#   The following two commands are equivalent and demonstrate building
68#   in a directory outside of the source tree.  The '-C' option tells
69#   scons to chdir to the specified directory to find this SConstruct
70#   file.
71#   % cd <path-to-src>/gem5 ; scons /local/foo/build/ALPHA/gem5.debug
72#   % cd /local/foo/build/ALPHA; scons -C <path-to-src>/gem5 gem5.debug
73#
74# You can use 'scons -H' to print scons options.  If you're in this
75# 'gem5' directory (or use -u or -C to tell scons where to find this
76# file), you can use 'scons -h' to print all the gem5-specific build
77# options as well.
78#
79###################################################
80
81from __future__ import print_function
82
83# Global Python includes
84import itertools
85import os
86import re
87import shutil
88import subprocess
89import sys
90
91from os import mkdir, environ
92from os.path import abspath, basename, dirname, expanduser, normpath
93from os.path import exists,  isdir, isfile
94from os.path import join as joinpath, split as splitpath
95
96# SCons includes
97import SCons
98import SCons.Node
99
100from m5.util import compareVersions, readCommand
101
102help_texts = {
103    "options" : "",
104    "global_vars" : "",
105    "local_vars" : ""
106}
107
108Export("help_texts")
109
110
111# There's a bug in scons in that (1) by default, the help texts from
112# AddOption() are supposed to be displayed when you type 'scons -h'
113# and (2) you can override the help displayed by 'scons -h' using the
114# Help() function, but these two features are incompatible: once
115# you've overridden the help text using Help(), there's no way to get
116# at the help texts from AddOptions.  See:
117#     http://scons.tigris.org/issues/show_bug.cgi?id=2356
118#     http://scons.tigris.org/issues/show_bug.cgi?id=2611
119# This hack lets us extract the help text from AddOptions and
120# re-inject it via Help().  Ideally someday this bug will be fixed and
121# we can just use AddOption directly.
122def AddLocalOption(*args, **kwargs):
123    col_width = 30
124
125    help = "  " + ", ".join(args)
126    if "help" in kwargs:
127        length = len(help)
128        if length >= col_width:
129            help += "\n" + " " * col_width
130        else:
131            help += " " * (col_width - length)
132        help += kwargs["help"]
133    help_texts["options"] += help + "\n"
134
135    AddOption(*args, **kwargs)
136
137AddLocalOption('--colors', dest='use_colors', action='store_true',
138               help="Add color to abbreviated scons output")
139AddLocalOption('--no-colors', dest='use_colors', action='store_false',
140               help="Don't add color to abbreviated scons output")
141AddLocalOption('--with-cxx-config', dest='with_cxx_config',
142               action='store_true',
143               help="Build with support for C++-based configuration")
144AddLocalOption('--default', dest='default', type='string', action='store',
145               help='Override which build_opts file to use for defaults')
146AddLocalOption('--ignore-style', dest='ignore_style', action='store_true',
147               help='Disable style checking hooks')
148AddLocalOption('--gold-linker', dest='gold_linker', action='store_true',
149               help='Use the gold linker')
150AddLocalOption('--no-lto', dest='no_lto', action='store_true',
151               help='Disable Link-Time Optimization for fast')
152AddLocalOption('--force-lto', dest='force_lto', action='store_true',
153               help='Use Link-Time Optimization instead of partial linking' +
154                    ' when the compiler doesn\'t support using them together.')
155AddLocalOption('--update-ref', dest='update_ref', action='store_true',
156               help='Update test reference outputs')
157AddLocalOption('--verbose', dest='verbose', action='store_true',
158               help='Print full tool command lines')
159AddLocalOption('--without-python', dest='without_python',
160               action='store_true',
161               help='Build without Python configuration support')
162AddLocalOption('--without-tcmalloc', dest='without_tcmalloc',
163               action='store_true',
164               help='Disable linking against tcmalloc')
165AddLocalOption('--with-ubsan', dest='with_ubsan', action='store_true',
166               help='Build with Undefined Behavior Sanitizer if available')
167AddLocalOption('--with-asan', dest='with_asan', action='store_true',
168               help='Build with Address Sanitizer if available')
169
170if GetOption('no_lto') and GetOption('force_lto'):
171    print('--no-lto and --force-lto are mutually exclusive')
172    Exit(1)
173
174########################################################################
175#
176# Set up the main build environment.
177#
178########################################################################
179
180main = Environment()
181
182from gem5_scons import Transform
183from gem5_scons.util import get_termcap
184termcap = get_termcap()
185
186main_dict_keys = main.Dictionary().keys()
187
188# Check that we have a C/C++ compiler
189if not ('CC' in main_dict_keys and 'CXX' in main_dict_keys):
190    print("No C++ compiler installed (package g++ on Ubuntu and RedHat)")
191    Exit(1)
192
193###################################################
194#
195# Figure out which configurations to set up based on the path(s) of
196# the target(s).
197#
198###################################################
199
200# Find default configuration & binary.
201Default(environ.get('M5_DEFAULT_BINARY', 'build/ALPHA/gem5.debug'))
202
203# helper function: find last occurrence of element in list
204def rfind(l, elt, offs = -1):
205    for i in range(len(l)+offs, 0, -1):
206        if l[i] == elt:
207            return i
208    raise ValueError, "element not found"
209
210# Take a list of paths (or SCons Nodes) and return a list with all
211# paths made absolute and ~-expanded.  Paths will be interpreted
212# relative to the launch directory unless a different root is provided
213def makePathListAbsolute(path_list, root=GetLaunchDir()):
214    return [abspath(joinpath(root, expanduser(str(p))))
215            for p in path_list]
216
217# Each target must have 'build' in the interior of the path; the
218# directory below this will determine the build parameters.  For
219# example, for target 'foo/bar/build/ALPHA_SE/arch/alpha/blah.do' we
220# recognize that ALPHA_SE specifies the configuration because it
221# follow 'build' in the build path.
222
223# The funky assignment to "[:]" is needed to replace the list contents
224# in place rather than reassign the symbol to a new list, which
225# doesn't work (obviously!).
226BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
227
228# Generate a list of the unique build roots and configs that the
229# collected targets reference.
230variant_paths = []
231build_root = None
232for t in BUILD_TARGETS:
233    path_dirs = t.split('/')
234    try:
235        build_top = rfind(path_dirs, 'build', -2)
236    except:
237        print("Error: no non-leaf 'build' dir found on target path", t)
238        Exit(1)
239    this_build_root = joinpath('/',*path_dirs[:build_top+1])
240    if not build_root:
241        build_root = this_build_root
242    else:
243        if this_build_root != build_root:
244            print("Error: build targets not under same build root\n"
245                  "  %s\n  %s" % (build_root, this_build_root))
246            Exit(1)
247    variant_path = joinpath('/',*path_dirs[:build_top+2])
248    if variant_path not in variant_paths:
249        variant_paths.append(variant_path)
250
251# Make sure build_root exists (might not if this is the first build there)
252if not isdir(build_root):
253    mkdir(build_root)
254main['BUILDROOT'] = build_root
255
256Export('main')
257
258main.SConsignFile(joinpath(build_root, "sconsign"))
259
260# Default duplicate option is to use hard links, but this messes up
261# when you use emacs to edit a file in the target dir, as emacs moves
262# file to file~ then copies to file, breaking the link.  Symbolic
263# (soft) links work better.
264main.SetOption('duplicate', 'soft-copy')
265
266#
267# Set up global sticky variables... these are common to an entire build
268# tree (not specific to a particular build like ALPHA_SE)
269#
270
271global_vars_file = joinpath(build_root, 'variables.global')
272
273global_vars = Variables(global_vars_file, args=ARGUMENTS)
274
275global_vars.AddVariables(
276    ('CC', 'C compiler', environ.get('CC', main['CC'])),
277    ('CXX', 'C++ compiler', environ.get('CXX', main['CXX'])),
278    ('PROTOC', 'protoc tool', environ.get('PROTOC', 'protoc')),
279    ('BATCH', 'Use batch pool for build and tests', False),
280    ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
281    ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),
282    ('EXTRAS', 'Add extra directories to the compilation', '')
283    )
284
285# Update main environment with values from ARGUMENTS & global_vars_file
286global_vars.Update(main)
287help_texts["global_vars"] += global_vars.GenerateHelpText(main)
288
289# Save sticky variable settings back to current variables file
290global_vars.Save(global_vars_file, main)
291
292# Parse EXTRAS variable to build list of all directories where we're
293# look for sources etc.  This list is exported as extras_dir_list.
294base_dir = main.srcdir.abspath
295if main['EXTRAS']:
296    extras_dir_list = makePathListAbsolute(main['EXTRAS'].split(':'))
297else:
298    extras_dir_list = []
299
300Export('base_dir')
301Export('extras_dir_list')
302
303# the ext directory should be on the #includes path
304main.Append(CPPPATH=[Dir('ext')])
305
306# Add shared top-level headers
307main.Prepend(CPPPATH=Dir('include'))
308
309if GetOption('verbose'):
310    def MakeAction(action, string, *args, **kwargs):
311        return Action(action, *args, **kwargs)
312else:
313    MakeAction = Action
314    main['CCCOMSTR']        = Transform("CC")
315    main['CXXCOMSTR']       = Transform("CXX")
316    main['ASCOMSTR']        = Transform("AS")
317    main['ARCOMSTR']        = Transform("AR", 0)
318    main['LINKCOMSTR']      = Transform("LINK", 0)
319    main['SHLINKCOMSTR']    = Transform("SHLINK", 0)
320    main['RANLIBCOMSTR']    = Transform("RANLIB", 0)
321    main['M4COMSTR']        = Transform("M4")
322    main['SHCCCOMSTR']      = Transform("SHCC")
323    main['SHCXXCOMSTR']     = Transform("SHCXX")
324Export('MakeAction')
325
326# Initialize the Link-Time Optimization (LTO) flags
327main['LTO_CCFLAGS'] = []
328main['LTO_LDFLAGS'] = []
329
330# According to the readme, tcmalloc works best if the compiler doesn't
331# assume that we're using the builtin malloc and friends. These flags
332# are compiler-specific, so we need to set them after we detect which
333# compiler we're using.
334main['TCMALLOC_CCFLAGS'] = []
335
336CXX_version = readCommand([main['CXX'],'--version'], exception=False)
337CXX_V = readCommand([main['CXX'],'-V'], exception=False)
338
339main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
340main['CLANG'] = CXX_version and CXX_version.find('clang') >= 0
341if main['GCC'] + main['CLANG'] > 1:
342    print('Error: How can we have two at the same time?')
343    Exit(1)
344
345# Set up default C++ compiler flags
346if main['GCC'] or main['CLANG']:
347    # As gcc and clang share many flags, do the common parts here
348    main.Append(CCFLAGS=['-pipe'])
349    main.Append(CCFLAGS=['-fno-strict-aliasing'])
350    # Enable -Wall and -Wextra and then disable the few warnings that
351    # we consistently violate
352    main.Append(CCFLAGS=['-Wall', '-Wundef', '-Wextra',
353                         '-Wno-sign-compare', '-Wno-unused-parameter'])
354    # We always compile using C++11
355    main.Append(CXXFLAGS=['-std=c++11'])
356    if sys.platform.startswith('freebsd'):
357        main.Append(CCFLAGS=['-I/usr/local/include'])
358        main.Append(CXXFLAGS=['-I/usr/local/include'])
359
360    main['FILTER_PSHLINKFLAGS'] = lambda x: str(x).replace(' -shared', '')
361    main['PSHLINKFLAGS'] = main.subst('${FILTER_PSHLINKFLAGS(SHLINKFLAGS)}')
362    if GetOption('gold_linker'):
363        main.Append(LINKFLAGS='-fuse-ld=gold')
364    main['PLINKFLAGS'] = main.subst('${LINKFLAGS}')
365    shared_partial_flags = ['-r', '-nostdlib']
366    main.Append(PSHLINKFLAGS=shared_partial_flags)
367    main.Append(PLINKFLAGS=shared_partial_flags)
368
369    # Treat warnings as errors but white list some warnings that we
370    # want to allow (e.g., deprecation warnings).
371    main.Append(CCFLAGS=['-Werror',
372                         '-Wno-error=deprecated-declarations',
373                         '-Wno-error=deprecated',
374                        ])
375else:
376    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
377    print("Don't know what compiler options to use for your compiler.")
378    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
379    print(termcap.Yellow + '       version:' + termcap.Normal, end = ' ')
380    if not CXX_version:
381        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
382              termcap.Normal)
383    else:
384        print(CXX_version.replace('\n', '<nl>'))
385    print("       If you're trying to use a compiler other than GCC")
386    print("       or clang, there appears to be something wrong with your")
387    print("       environment.")
388    print("       ")
389    print("       If you are trying to use a compiler other than those listed")
390    print("       above you will need to ease fix SConstruct and ")
391    print("       src/SConscript to support that compiler.")
392    Exit(1)
393
394if main['GCC']:
395    # Check for a supported version of gcc. >= 4.8 is chosen for its
396    # level of c++11 support. See
397    # http://gcc.gnu.org/projects/cxx0x.html for details.
398    gcc_version = readCommand([main['CXX'], '-dumpversion'], exception=False)
399    if compareVersions(gcc_version, "4.8") < 0:
400        print('Error: gcc version 4.8 or newer required.')
401        print('       Installed version: ', gcc_version)
402        Exit(1)
403
404    main['GCC_VERSION'] = gcc_version
405
406    if compareVersions(gcc_version, '4.9') >= 0:
407        # Incremental linking with LTO is currently broken in gcc versions
408        # 4.9 and above. A version where everything works completely hasn't
409        # yet been identified.
410        #
411        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67548
412        main['BROKEN_INCREMENTAL_LTO'] = True
413    if compareVersions(gcc_version, '6.0') >= 0:
414        # gcc versions 6.0 and greater accept an -flinker-output flag which
415        # selects what type of output the linker should generate. This is
416        # necessary for incremental lto to work, but is also broken in
417        # current versions of gcc. It may not be necessary in future
418        # versions. We add it here since it might be, and as a reminder that
419        # it exists. It's excluded if lto is being forced.
420        #
421        # https://gcc.gnu.org/gcc-6/changes.html
422        # https://gcc.gnu.org/ml/gcc-patches/2015-11/msg03161.html
423        # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69866
424        if not GetOption('force_lto'):
425            main.Append(PSHLINKFLAGS='-flinker-output=rel')
426            main.Append(PLINKFLAGS='-flinker-output=rel')
427
428    # Make sure we warn if the user has requested to compile with the
429    # Undefined Benahvior Sanitizer and this version of gcc does not
430    # support it.
431    if GetOption('with_ubsan') and \
432            compareVersions(gcc_version, '4.9') < 0:
433        print(termcap.Yellow + termcap.Bold +
434            'Warning: UBSan is only supported using gcc 4.9 and later.' +
435            termcap.Normal)
436
437    disable_lto = GetOption('no_lto')
438    if not disable_lto and main.get('BROKEN_INCREMENTAL_LTO', False) and \
439            not GetOption('force_lto'):
440        print(termcap.Yellow + termcap.Bold +
441            'Warning: Your compiler doesn\'t support incremental linking' +
442            ' and lto at the same time, so lto is being disabled. To force' +
443            ' lto on anyway, use the --force-lto option. That will disable' +
444            ' partial linking.' +
445            termcap.Normal)
446        disable_lto = True
447
448    # Add the appropriate Link-Time Optimization (LTO) flags
449    # unless LTO is explicitly turned off. Note that these flags
450    # are only used by the fast target.
451    if not disable_lto:
452        # Pass the LTO flag when compiling to produce GIMPLE
453        # output, we merely create the flags here and only append
454        # them later
455        main['LTO_CCFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
456
457        # Use the same amount of jobs for LTO as we are running
458        # scons with
459        main['LTO_LDFLAGS'] = ['-flto=%d' % GetOption('num_jobs')]
460
461    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin-malloc', '-fno-builtin-calloc',
462                                  '-fno-builtin-realloc', '-fno-builtin-free'])
463
464    # The address sanitizer is available for gcc >= 4.8
465    if GetOption('with_asan'):
466        if GetOption('with_ubsan') and \
467                compareVersions(main['GCC_VERSION'], '4.9') >= 0:
468            main.Append(CCFLAGS=['-fsanitize=address,undefined',
469                                 '-fno-omit-frame-pointer'],
470                        LINKFLAGS='-fsanitize=address,undefined')
471        else:
472            main.Append(CCFLAGS=['-fsanitize=address',
473                                 '-fno-omit-frame-pointer'],
474                        LINKFLAGS='-fsanitize=address')
475    # Only gcc >= 4.9 supports UBSan, so check both the version
476    # and the command-line option before adding the compiler and
477    # linker flags.
478    elif GetOption('with_ubsan') and \
479            compareVersions(main['GCC_VERSION'], '4.9') >= 0:
480        main.Append(CCFLAGS='-fsanitize=undefined')
481        main.Append(LINKFLAGS='-fsanitize=undefined')
482
483elif main['CLANG']:
484    # Check for a supported version of clang, >= 3.1 is needed to
485    # support similar features as gcc 4.8. See
486    # http://clang.llvm.org/cxx_status.html for details
487    clang_version_re = re.compile(".* version (\d+\.\d+)")
488    clang_version_match = clang_version_re.search(CXX_version)
489    if (clang_version_match):
490        clang_version = clang_version_match.groups()[0]
491        if compareVersions(clang_version, "3.1") < 0:
492            print('Error: clang version 3.1 or newer required.')
493            print('       Installed version:', clang_version)
494            Exit(1)
495    else:
496        print('Error: Unable to determine clang version.')
497        Exit(1)
498
499    # clang has a few additional warnings that we disable, extraneous
500    # parantheses are allowed due to Ruby's printing of the AST,
501    # finally self assignments are allowed as the generated CPU code
502    # is relying on this
503    main.Append(CCFLAGS=['-Wno-parentheses',
504                         '-Wno-self-assign',
505                         # Some versions of libstdc++ (4.8?) seem to
506                         # use struct hash and class hash
507                         # interchangeably.
508                         '-Wno-mismatched-tags',
509                         ])
510
511    main.Append(TCMALLOC_CCFLAGS=['-fno-builtin'])
512
513    # On Mac OS X/Darwin we need to also use libc++ (part of XCode) as
514    # opposed to libstdc++, as the later is dated.
515    if sys.platform == "darwin":
516        main.Append(CXXFLAGS=['-stdlib=libc++'])
517        main.Append(LIBS=['c++'])
518
519    # On FreeBSD we need libthr.
520    if sys.platform.startswith('freebsd'):
521        main.Append(LIBS=['thr'])
522
523    # We require clang >= 3.1, so there is no need to check any
524    # versions here.
525    if GetOption('with_ubsan'):
526        if GetOption('with_asan'):
527            main.Append(CCFLAGS=['-fsanitize=address,undefined',
528                                 '-fno-omit-frame-pointer'],
529                       LINKFLAGS='-fsanitize=address,undefined')
530        else:
531            main.Append(CCFLAGS='-fsanitize=undefined',
532                        LINKFLAGS='-fsanitize=undefined')
533
534    elif GetOption('with_asan'):
535        main.Append(CCFLAGS=['-fsanitize=address',
536                             '-fno-omit-frame-pointer'],
537                   LINKFLAGS='-fsanitize=address')
538
539else:
540    print(termcap.Yellow + termcap.Bold + 'Error' + termcap.Normal, end=' ')
541    print("Don't know what compiler options to use for your compiler.")
542    print(termcap.Yellow + '       compiler:' + termcap.Normal, main['CXX'])
543    print(termcap.Yellow + '       version:' + termcap.Normal, end=' ')
544    if not CXX_version:
545        print(termcap.Yellow + termcap.Bold + "COMMAND NOT FOUND!" +
546              termcap.Normal)
547    else:
548        print(CXX_version.replace('\n', '<nl>'))
549    print("       If you're trying to use a compiler other than GCC")
550    print("       or clang, there appears to be something wrong with your")
551    print("       environment.")
552    print("       ")
553    print("       If you are trying to use a compiler other than those listed")
554    print("       above you will need to ease fix SConstruct and ")
555    print("       src/SConscript to support that compiler.")
556    Exit(1)
557
558# Set up common yacc/bison flags (needed for Ruby)
559main['YACCFLAGS'] = '-d'
560main['YACCHXXFILESUFFIX'] = '.hh'
561
562# Do this after we save setting back, or else we'll tack on an
563# extra 'qdo' every time we run scons.
564if main['BATCH']:
565    main['CC']     = main['BATCH_CMD'] + ' ' + main['CC']
566    main['CXX']    = main['BATCH_CMD'] + ' ' + main['CXX']
567    main['AS']     = main['BATCH_CMD'] + ' ' + main['AS']
568    main['AR']     = main['BATCH_CMD'] + ' ' + main['AR']
569    main['RANLIB'] = main['BATCH_CMD'] + ' ' + main['RANLIB']
570
571if sys.platform == 'cygwin':
572    # cygwin has some header file issues...
573    main.Append(CCFLAGS=["-Wno-uninitialized"])
574
575# Check for the protobuf compiler
576protoc_version = readCommand([main['PROTOC'], '--version'],
577                             exception='').split()
578
579# First two words should be "libprotoc x.y.z"
580if len(protoc_version) < 2 or protoc_version[0] != 'libprotoc':
581    print(termcap.Yellow + termcap.Bold +
582        'Warning: Protocol buffer compiler (protoc) not found.\n' +
583        '         Please install protobuf-compiler for tracing support.' +
584        termcap.Normal)
585    main['PROTOC'] = False
586else:
587    # Based on the availability of the compress stream wrappers,
588    # require 2.1.0
589    min_protoc_version = '2.1.0'
590    if compareVersions(protoc_version[1], min_protoc_version) < 0:
591        print(termcap.Yellow + termcap.Bold +
592            'Warning: protoc version', min_protoc_version,
593            'or newer required.\n' +
594            '         Installed version:', protoc_version[1],
595            termcap.Normal)
596        main['PROTOC'] = False
597    else:
598        # Attempt to determine the appropriate include path and
599        # library path using pkg-config, that means we also need to
600        # check for pkg-config. Note that it is possible to use
601        # protobuf without the involvement of pkg-config. Later on we
602        # check go a library config check and at that point the test
603        # will fail if libprotobuf cannot be found.
604        if readCommand(['pkg-config', '--version'], exception=''):
605            try:
606                # Attempt to establish what linking flags to add for protobuf
607                # using pkg-config
608                main.ParseConfig('pkg-config --cflags --libs-only-L protobuf')
609            except:
610                print(termcap.Yellow + termcap.Bold +
611                    'Warning: pkg-config could not get protobuf flags.' +
612                    termcap.Normal)
613
614
615# Check for 'timeout' from GNU coreutils. If present, regressions will
616# be run with a time limit. We require version 8.13 since we rely on
617# support for the '--foreground' option.
618if sys.platform.startswith('freebsd'):
619    timeout_lines = readCommand(['gtimeout', '--version'],
620                                exception='').splitlines()
621else:
622    timeout_lines = readCommand(['timeout', '--version'],
623                                exception='').splitlines()
624# Get the first line and tokenize it
625timeout_version = timeout_lines[0].split() if timeout_lines else []
626main['TIMEOUT'] =  timeout_version and \
627    compareVersions(timeout_version[-1], '8.13') >= 0
628
629# Add a custom Check function to test for structure members.
630def CheckMember(context, include, decl, member, include_quotes="<>"):
631    context.Message("Checking for member %s in %s..." %
632                    (member, decl))
633    text = """
634#include %(header)s
635int main(){
636  %(decl)s test;
637  (void)test.%(member)s;
638  return 0;
639};
640""" % { "header" : include_quotes[0] + include + include_quotes[1],
641        "decl" : decl,
642        "member" : member,
643        }
644
645    ret = context.TryCompile(text, extension=".cc")
646    context.Result(ret)
647    return ret
648
649# Platform-specific configuration.  Note again that we assume that all
650# builds under a given build root run on the same host platform.
651conf = Configure(main,
652                 conf_dir = joinpath(build_root, '.scons_config'),
653                 log_file = joinpath(build_root, 'scons_config.log'),
654                 custom_tests = {
655        'CheckMember' : CheckMember,
656        })
657
658# Check if we should compile a 64 bit binary on Mac OS X/Darwin
659try:
660    import platform
661    uname = platform.uname()
662    if uname[0] == 'Darwin' and compareVersions(uname[2], '9.0.0') >= 0:
663        if int(readCommand('sysctl -n hw.cpu64bit_capable')[0]):
664            main.Append(CCFLAGS=['-arch', 'x86_64'])
665            main.Append(CFLAGS=['-arch', 'x86_64'])
666            main.Append(LINKFLAGS=['-arch', 'x86_64'])
667            main.Append(ASFLAGS=['-arch', 'x86_64'])
668except:
669    pass
670
671# Recent versions of scons substitute a "Null" object for Configure()
672# when configuration isn't necessary, e.g., if the "--help" option is
673# present.  Unfortuantely this Null object always returns false,
674# breaking all our configuration checks.  We replace it with our own
675# more optimistic null object that returns True instead.
676if not conf:
677    def NullCheck(*args, **kwargs):
678        return True
679
680    class NullConf:
681        def __init__(self, env):
682            self.env = env
683        def Finish(self):
684            return self.env
685        def __getattr__(self, mname):
686            return NullCheck
687
688    conf = NullConf(main)
689
690# Cache build files in the supplied directory.
691if main['M5_BUILD_CACHE']:
692    print('Using build cache located at', main['M5_BUILD_CACHE'])
693    CacheDir(main['M5_BUILD_CACHE'])
694
695main['USE_PYTHON'] = not GetOption('without_python')
696if main['USE_PYTHON']:
697    # Find Python include and library directories for embedding the
698    # interpreter. We rely on python-config to resolve the appropriate
699    # includes and linker flags. ParseConfig does not seem to understand
700    # the more exotic linker flags such as -Xlinker and -export-dynamic so
701    # we add them explicitly below. If you want to link in an alternate
702    # version of python, see above for instructions on how to invoke
703    # scons with the appropriate PATH set.
704    #
705    # First we check if python2-config exists, else we use python-config
706    python_config = readCommand(['which', 'python2-config'],
707                                exception='').strip()
708    if not os.path.exists(python_config):
709        python_config = readCommand(['which', 'python-config'],
710                                    exception='').strip()
711    py_includes = readCommand([python_config, '--includes'],
712                              exception='').split()
713    # Strip the -I from the include folders before adding them to the
714    # CPPPATH
715    main.Append(CPPPATH=map(lambda inc: inc[2:], py_includes))
716
717    # Read the linker flags and split them into libraries and other link
718    # flags. The libraries are added later through the call the CheckLib.
719    py_ld_flags = readCommand([python_config, '--ldflags'],
720        exception='').split()
721    py_libs = []
722    for lib in py_ld_flags:
723         if not lib.startswith('-l'):
724             main.Append(LINKFLAGS=[lib])
725         else:
726             lib = lib[2:]
727             if lib not in py_libs:
728                 py_libs.append(lib)
729
730    # verify that this stuff works
731    if not conf.CheckHeader('Python.h', '<>'):
732        print("Error: Check failed for Python.h header in", py_includes)
733        print("Two possible reasons:")
734        print("1. Python headers are not installed (You can install the "
735              "package python-dev on Ubuntu and RedHat)")
736        print("2. SCons is using a wrong C compiler. This can happen if "
737              "CC has the wrong value.")
738        print("CC = %s" % main['CC'])
739        Exit(1)
740
741    for lib in py_libs:
742        if not conf.CheckLib(lib):
743            print("Error: can't find library %s required by python" % lib)
744            Exit(1)
745
746# On Solaris you need to use libsocket for socket ops
747if not conf.CheckLibWithHeader(None, 'sys/socket.h', 'C++', 'accept(0,0,0);'):
748   if not conf.CheckLibWithHeader('socket', 'sys/socket.h', 'C++', 'accept(0,0,0);'):
749       print("Can't find library with socket calls (e.g. accept())")
750       Exit(1)
751
752# Check for zlib.  If the check passes, libz will be automatically
753# added to the LIBS environment variable.
754if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
755    print('Error: did not find needed zlib compression library '
756          'and/or zlib.h header file.')
757    print('       Please install zlib and try again.')
758    Exit(1)
759
760# If we have the protobuf compiler, also make sure we have the
761# development libraries. If the check passes, libprotobuf will be
762# automatically added to the LIBS environment variable. After
763# this, we can use the HAVE_PROTOBUF flag to determine if we have
764# got both protoc and libprotobuf available.
765main['HAVE_PROTOBUF'] = main['PROTOC'] and \
766    conf.CheckLibWithHeader('protobuf', 'google/protobuf/message.h',
767                            'C++', 'GOOGLE_PROTOBUF_VERIFY_VERSION;')
768
769# Valgrind gets much less confused if you tell it when you're using
770# alternative stacks.
771main['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
772
773# If we have the compiler but not the library, print another warning.
774if main['PROTOC'] and not main['HAVE_PROTOBUF']:
775    print(termcap.Yellow + termcap.Bold +
776        'Warning: did not find protocol buffer library and/or headers.\n' +
777    '       Please install libprotobuf-dev for tracing support.' +
778    termcap.Normal)
779
780# Check for librt.
781have_posix_clock = \
782    conf.CheckLibWithHeader(None, 'time.h', 'C',
783                            'clock_nanosleep(0,0,NULL,NULL);') or \
784    conf.CheckLibWithHeader('rt', 'time.h', 'C',
785                            'clock_nanosleep(0,0,NULL,NULL);')
786
787have_posix_timers = \
788    conf.CheckLibWithHeader([None, 'rt'], [ 'time.h', 'signal.h' ], 'C',
789                            'timer_create(CLOCK_MONOTONIC, NULL, NULL);')
790
791if not GetOption('without_tcmalloc'):
792    if conf.CheckLib('tcmalloc'):
793        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
794    elif conf.CheckLib('tcmalloc_minimal'):
795        main.Append(CCFLAGS=main['TCMALLOC_CCFLAGS'])
796    else:
797        print(termcap.Yellow + termcap.Bold +
798              "You can get a 12% performance improvement by "
799              "installing tcmalloc (libgoogle-perftools-dev package "
800              "on Ubuntu or RedHat)." + termcap.Normal)
801
802
803# Detect back trace implementations. The last implementation in the
804# list will be used by default.
805backtrace_impls = [ "none" ]
806
807backtrace_checker = 'char temp;' + \
808    ' backtrace_symbols_fd((void*)&temp, 0, 0);'
809if conf.CheckLibWithHeader(None, 'execinfo.h', 'C', backtrace_checker):
810    backtrace_impls.append("glibc")
811elif conf.CheckLibWithHeader('execinfo', 'execinfo.h', 'C',
812                             backtrace_checker):
813    # NetBSD and FreeBSD need libexecinfo.
814    backtrace_impls.append("glibc")
815    main.Append(LIBS=['execinfo'])
816
817if backtrace_impls[-1] == "none":
818    default_backtrace_impl = "none"
819    print(termcap.Yellow + termcap.Bold +
820        "No suitable back trace implementation found." +
821        termcap.Normal)
822
823if not have_posix_clock:
824    print("Can't find library for POSIX clocks.")
825
826# Check for <fenv.h> (C99 FP environment control)
827have_fenv = conf.CheckHeader('fenv.h', '<>')
828if not have_fenv:
829    print("Warning: Header file <fenv.h> not found.")
830    print("         This host has no IEEE FP rounding mode control.")
831
832# Check for <png.h> (libpng library needed if wanting to dump
833# frame buffer image in png format)
834have_png = conf.CheckHeader('png.h', '<>')
835if not have_png:
836    print("Warning: Header file <png.h> not found.")
837    print("         This host has no libpng library.")
838    print("         Disabling support for PNG framebuffers.")
839
840# Check if we should enable KVM-based hardware virtualization. The API
841# we rely on exists since version 2.6.36 of the kernel, but somehow
842# the KVM_API_VERSION does not reflect the change. We test for one of
843# the types as a fall back.
844have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
845if not have_kvm:
846    print("Info: Compatible header file <linux/kvm.h> not found, "
847          "disabling KVM support.")
848
849# Check if the TUN/TAP driver is available.
850have_tuntap = conf.CheckHeader('linux/if_tun.h', '<>')
851if not have_tuntap:
852    print("Info: Compatible header file <linux/if_tun.h> not found.")
853
854# x86 needs support for xsave. We test for the structure here since we
855# won't be able to run new tests by the time we know which ISA we're
856# targeting.
857have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
858                                    '#include <linux/kvm.h>') != 0
859
860# Check if the requested target ISA is compatible with the host
861def is_isa_kvm_compatible(isa):
862    try:
863        import platform
864        host_isa = platform.machine()
865    except:
866        print("Warning: Failed to determine host ISA.")
867        return False
868
869    if not have_posix_timers:
870        print("Warning: Can not enable KVM, host seems to lack support "
871              "for POSIX timers")
872        return False
873
874    if isa == "arm":
875        return host_isa in ( "armv7l", "aarch64" )
876    elif isa == "x86":
877        if host_isa != "x86_64":
878            return False
879
880        if not have_kvm_xsave:
881            print("KVM on x86 requires xsave support in kernel headers.")
882            return False
883
884        return True
885    else:
886        return False
887
888
889# Check if the exclude_host attribute is available. We want this to
890# get accurate instruction counts in KVM.
891main['HAVE_PERF_ATTR_EXCLUDE_HOST'] = conf.CheckMember(
892    'linux/perf_event.h', 'struct perf_event_attr', 'exclude_host')
893
894
895######################################################################
896#
897# Finish the configuration
898#
899main = conf.Finish()
900
901######################################################################
902#
903# Collect all non-global variables
904#
905
906# Define the universe of supported ISAs
907all_isa_list = [ ]
908all_gpu_isa_list = [ ]
909Export('all_isa_list')
910Export('all_gpu_isa_list')
911
912class CpuModel(object):
913    '''The CpuModel class encapsulates everything the ISA parser needs to
914    know about a particular CPU model.'''
915
916    # Dict of available CPU model objects.  Accessible as CpuModel.dict.
917    dict = {}
918
919    # Constructor.  Automatically adds models to CpuModel.dict.
920    def __init__(self, name, default=False):
921        self.name = name           # name of model
922
923        # This cpu is enabled by default
924        self.default = default
925
926        # Add self to dict
927        if name in CpuModel.dict:
928            raise AttributeError, "CpuModel '%s' already registered" % name
929        CpuModel.dict[name] = self
930
931Export('CpuModel')
932
933# Sticky variables get saved in the variables file so they persist from
934# one invocation to the next (unless overridden, in which case the new
935# value becomes sticky).
936sticky_vars = Variables(args=ARGUMENTS)
937Export('sticky_vars')
938
939# Sticky variables that should be exported
940export_vars = []
941Export('export_vars')
942
943# For Ruby
944all_protocols = []
945Export('all_protocols')
946protocol_dirs = []
947Export('protocol_dirs')
948slicc_includes = []
949Export('slicc_includes')
950
951# Walk the tree and execute all SConsopts scripts that wil add to the
952# above variables
953if GetOption('verbose'):
954    print("Reading SConsopts")
955for bdir in [ base_dir ] + extras_dir_list:
956    if not isdir(bdir):
957        print("Error: directory '%s' does not exist" % bdir)
958        Exit(1)
959    for root, dirs, files in os.walk(bdir):
960        if 'SConsopts' in files:
961            if GetOption('verbose'):
962                print("Reading", joinpath(root, 'SConsopts'))
963            SConscript(joinpath(root, 'SConsopts'))
964
965all_isa_list.sort()
966all_gpu_isa_list.sort()
967
968sticky_vars.AddVariables(
969    EnumVariable('TARGET_ISA', 'Target ISA', 'alpha', all_isa_list),
970    EnumVariable('TARGET_GPU_ISA', 'Target GPU ISA', 'hsail', all_gpu_isa_list),
971    ListVariable('CPU_MODELS', 'CPU models',
972                 sorted(n for n,m in CpuModel.dict.iteritems() if m.default),
973                 sorted(CpuModel.dict.keys())),
974    BoolVariable('EFENCE', 'Link with Electric Fence malloc debugger',
975                 False),
976    BoolVariable('SS_COMPATIBLE_FP',
977                 'Make floating-point results compatible with SimpleScalar',
978                 False),
979    BoolVariable('USE_SSE2',
980                 'Compile for SSE2 (-msse2) to get IEEE FP on x86 hosts',
981                 False),
982    BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks', have_posix_clock),
983    BoolVariable('USE_FENV', 'Use <fenv.h> IEEE mode control', have_fenv),
984    BoolVariable('USE_PNG',  'Enable support for PNG images', have_png),
985    BoolVariable('CP_ANNOTATE', 'Enable critical path annotation capability',
986                 False),
987    BoolVariable('USE_KVM', 'Enable hardware virtualized (KVM) CPU models',
988                 have_kvm),
989    BoolVariable('USE_TUNTAP',
990                 'Enable using a tap device to bridge to the host network',
991                 have_tuntap),
992    BoolVariable('BUILD_GPU', 'Build the compute-GPU model', False),
993    EnumVariable('PROTOCOL', 'Coherence protocol for Ruby', 'None',
994                  all_protocols),
995    EnumVariable('BACKTRACE_IMPL', 'Post-mortem dump implementation',
996                 backtrace_impls[-1], backtrace_impls)
997    )
998
999# These variables get exported to #defines in config/*.hh (see src/SConscript).
1000export_vars += ['USE_FENV', 'SS_COMPATIBLE_FP', 'TARGET_ISA', 'TARGET_GPU_ISA',
1001                'CP_ANNOTATE', 'USE_POSIX_CLOCK', 'USE_KVM', 'USE_TUNTAP',
1002                'PROTOCOL', 'HAVE_PROTOBUF', 'HAVE_VALGRIND',
1003                'HAVE_PERF_ATTR_EXCLUDE_HOST', 'USE_PNG']
1004
1005###################################################
1006#
1007# Define a SCons builder for configuration flag headers.
1008#
1009###################################################
1010
1011# This function generates a config header file that #defines the
1012# variable symbol to the current variable setting (0 or 1).  The source
1013# operands are the name of the variable and a Value node containing the
1014# value of the variable.
1015def build_config_file(target, source, env):
1016    (variable, value) = [s.get_contents() for s in source]
1017    f = file(str(target[0]), 'w')
1018    print('#define', variable, value, file=f)
1019    f.close()
1020    return None
1021
1022# Combine the two functions into a scons Action object.
1023config_action = MakeAction(build_config_file, Transform("CONFIG H", 2))
1024
1025# The emitter munges the source & target node lists to reflect what
1026# we're really doing.
1027def config_emitter(target, source, env):
1028    # extract variable name from Builder arg
1029    variable = str(target[0])
1030    # True target is config header file
1031    target = joinpath('config', variable.lower() + '.hh')
1032    val = env[variable]
1033    if isinstance(val, bool):
1034        # Force value to 0/1
1035        val = int(val)
1036    elif isinstance(val, str):
1037        val = '"' + val + '"'
1038
1039    # Sources are variable name & value (packaged in SCons Value nodes)
1040    return ([target], [Value(variable), Value(val)])
1041
1042config_builder = Builder(emitter = config_emitter, action = config_action)
1043
1044main.Append(BUILDERS = { 'ConfigFile' : config_builder })
1045
1046###################################################
1047#
1048# Builders for static and shared partially linked object files.
1049#
1050###################################################
1051
1052partial_static_builder = Builder(action=SCons.Defaults.LinkAction,
1053                                 src_suffix='$OBJSUFFIX',
1054                                 src_builder=['StaticObject', 'Object'],
1055                                 LINKFLAGS='$PLINKFLAGS',
1056                                 LIBS='')
1057
1058def partial_shared_emitter(target, source, env):
1059    for tgt in target:
1060        tgt.attributes.shared = 1
1061    return (target, source)
1062partial_shared_builder = Builder(action=SCons.Defaults.ShLinkAction,
1063                                 emitter=partial_shared_emitter,
1064                                 src_suffix='$SHOBJSUFFIX',
1065                                 src_builder='SharedObject',
1066                                 SHLINKFLAGS='$PSHLINKFLAGS',
1067                                 LIBS='')
1068
1069main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
1070                         'PartialStatic' : partial_static_builder })
1071
1072# builds in ext are shared across all configs in the build root.
1073ext_dir = abspath(joinpath(str(main.root), 'ext'))
1074ext_build_dirs = []
1075for root, dirs, files in os.walk(ext_dir):
1076    if 'SConscript' in files:
1077        build_dir = os.path.relpath(root, ext_dir)
1078        ext_build_dirs.append(build_dir)
1079        main.SConscript(joinpath(root, 'SConscript'),
1080                        variant_dir=joinpath(build_root, build_dir))
1081
1082main.Prepend(CPPPATH=Dir('ext/pybind11/include/'))
1083
1084###################################################
1085#
1086# This builder and wrapper method are used to set up a directory with
1087# switching headers. Those are headers which are in a generic location and
1088# that include more specific headers from a directory chosen at build time
1089# based on the current build settings.
1090#
1091###################################################
1092
1093def build_switching_header(target, source, env):
1094    path = str(target[0])
1095    subdir = str(source[0])
1096    dp, fp = os.path.split(path)
1097    dp = os.path.relpath(os.path.realpath(dp),
1098                         os.path.realpath(env['BUILDDIR']))
1099    with open(path, 'w') as hdr:
1100        print('#include "%s/%s/%s"' % (dp, subdir, fp), file=hdr)
1101
1102switching_header_action = MakeAction(build_switching_header,
1103                                     Transform('GENERATE'))
1104
1105switching_header_builder = Builder(action=switching_header_action,
1106                                   source_factory=Value,
1107                                   single_source=True)
1108
1109main.Append(BUILDERS = { 'SwitchingHeader': switching_header_builder })
1110
1111def switching_headers(self, headers, source):
1112    for header in headers:
1113        self.SwitchingHeader(header, source)
1114
1115main.AddMethod(switching_headers, 'SwitchingHeaders')
1116
1117###################################################
1118#
1119# Define build environments for selected configurations.
1120#
1121###################################################
1122
1123for variant_path in variant_paths:
1124    if not GetOption('silent'):
1125        print("Building in", variant_path)
1126
1127    # Make a copy of the build-root environment to use for this config.
1128    env = main.Clone()
1129    env['BUILDDIR'] = variant_path
1130
1131    # variant_dir is the tail component of build path, and is used to
1132    # determine the build parameters (e.g., 'ALPHA_SE')
1133    (build_root, variant_dir) = splitpath(variant_path)
1134
1135    # Set env variables according to the build directory config.
1136    sticky_vars.files = []
1137    # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
1138    # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
1139    # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
1140    current_vars_file = joinpath(build_root, 'variables', variant_dir)
1141    if isfile(current_vars_file):
1142        sticky_vars.files.append(current_vars_file)
1143        if not GetOption('silent'):
1144            print("Using saved variables file %s" % current_vars_file)
1145    elif variant_dir in ext_build_dirs:
1146        # Things in ext are built without a variant directory.
1147        continue
1148    else:
1149        # Build dir-specific variables file doesn't exist.
1150
1151        # Make sure the directory is there so we can create it later
1152        opt_dir = dirname(current_vars_file)
1153        if not isdir(opt_dir):
1154            mkdir(opt_dir)
1155
1156        # Get default build variables from source tree.  Variables are
1157        # normally determined by name of $VARIANT_DIR, but can be
1158        # overridden by '--default=' arg on command line.
1159        default = GetOption('default')
1160        opts_dir = joinpath(main.root.abspath, 'build_opts')
1161        if default:
1162            default_vars_files = [joinpath(build_root, 'variables', default),
1163                                  joinpath(opts_dir, default)]
1164        else:
1165            default_vars_files = [joinpath(opts_dir, variant_dir)]
1166        existing_files = filter(isfile, default_vars_files)
1167        if existing_files:
1168            default_vars_file = existing_files[0]
1169            sticky_vars.files.append(default_vars_file)
1170            print("Variables file %s not found,\n  using defaults in %s"
1171                  % (current_vars_file, default_vars_file))
1172        else:
1173            print("Error: cannot find variables file %s or "
1174                  "default file(s) %s"
1175                  % (current_vars_file, ' or '.join(default_vars_files)))
1176            Exit(1)
1177
1178    # Apply current variable settings to env
1179    sticky_vars.Update(env)
1180
1181    help_texts["local_vars"] += \
1182        "Build variables for %s:\n" % variant_dir \
1183                 + sticky_vars.GenerateHelpText(env)
1184
1185    # Process variable settings.
1186
1187    if not have_fenv and env['USE_FENV']:
1188        print("Warning: <fenv.h> not available; "
1189              "forcing USE_FENV to False in", variant_dir + ".")
1190        env['USE_FENV'] = False
1191
1192    if not env['USE_FENV']:
1193        print("Warning: No IEEE FP rounding mode control in",
1194              variant_dir + ".")
1195        print("         FP results may deviate slightly from other platforms.")
1196
1197    if not have_png and env['USE_PNG']:
1198        print("Warning: <png.h> not available; "
1199              "forcing USE_PNG to False in", variant_dir + ".")
1200        env['USE_PNG'] = False
1201
1202    if env['USE_PNG']:
1203        env.Append(LIBS=['png'])
1204
1205    if env['EFENCE']:
1206        env.Append(LIBS=['efence'])
1207
1208    if env['USE_KVM']:
1209        if not have_kvm:
1210            print("Warning: Can not enable KVM, host seems to "
1211                  "lack KVM support")
1212            env['USE_KVM'] = False
1213        elif not is_isa_kvm_compatible(env['TARGET_ISA']):
1214            print("Info: KVM support disabled due to unsupported host and "
1215                  "target ISA combination")
1216            env['USE_KVM'] = False
1217
1218    if env['USE_TUNTAP']:
1219        if not have_tuntap:
1220            print("Warning: Can't connect EtherTap with a tap device.")
1221            env['USE_TUNTAP'] = False
1222
1223    if env['BUILD_GPU']:
1224        env.Append(CPPDEFINES=['BUILD_GPU'])
1225
1226    # Warn about missing optional functionality
1227    if env['USE_KVM']:
1228        if not main['HAVE_PERF_ATTR_EXCLUDE_HOST']:
1229            print("Warning: perf_event headers lack support for the "
1230                  "exclude_host attribute. KVM instruction counts will "
1231                  "be inaccurate.")
1232
1233    # Save sticky variable settings back to current variables file
1234    sticky_vars.Save(current_vars_file, env)
1235
1236    if env['USE_SSE2']:
1237        env.Append(CCFLAGS=['-msse2'])
1238
1239    # The src/SConscript file sets up the build rules in 'env' according
1240    # to the configured variables.  It returns a list of environments,
1241    # one for each variant build (debug, opt, etc.)
1242    SConscript('src/SConscript', variant_dir = variant_path, exports = 'env')
1243
1244# base help text
1245Help('''
1246Usage: scons [scons options] [build variables] [target(s)]
1247
1248Extra scons options:
1249%(options)s
1250
1251Global build variables:
1252%(global_vars)s
1253
1254%(local_vars)s
1255''' % help_texts)
1256