summaryrefslogtreecommitdiff
path: root/eclass/flag-o-matic.eclass
blob: bef3abf69dde07912957161a811278f3e37f5da6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
# Copyright 1999-2023 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

# @ECLASS: flag-o-matic.eclass
# @MAINTAINER:
# toolchain@gentoo.org
# @SUPPORTED_EAPIS: 6 7 8
# @BLURB: common functions to manipulate and query toolchain flags
# @DESCRIPTION:
# This eclass contains a suite of functions to help developers sanely
# and safely manage toolchain flags in their builds.

case ${EAPI} in
	6|7|8) ;;
	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
esac

if [[ -z ${_FLAG_O_MATIC_ECLASS} ]]; then
_FLAG_O_MATIC_ECLASS=1

inherit toolchain-funcs

[[ ${EAPI} == [67] ]] && inherit eutils

# @FUNCTION: all-flag-vars
# @DESCRIPTION:
# Return all the flag variables that our high level functions operate on.
all-flag-vars() {
	echo {ADA,C,CPP,CXX,CCAS,F,FC,LD}FLAGS
}

# @FUNCTION: setup-allowed-flags
# @INTERNAL
# @DESCRIPTION:
# {C,CPP,CXX,CCAS,F,FC,LD}FLAGS that we allow in strip-flags
# Note: shell globs and character lists are allowed
setup-allowed-flags() {
	[[ ${EAPI} == [67] ]] ||
		die "Internal function ${FUNCNAME} is not available in EAPI ${EAPI}."
	_setup-allowed-flags "$@"
}

# @FUNCTION: _setup-allowed-flags
# @INTERNAL
# @DESCRIPTION:
# {C,CPP,CXX,CCAS,F,FC,LD}FLAGS that we allow in strip-flags
# Note: shell globs and character lists are allowed
_setup-allowed-flags() {
	ALLOWED_FLAGS=(
		-pipe -O '-O[123szg]' '-mcpu=*' '-march=*' '-mtune=*'
		-flto '-flto=*' -fno-lto

		# Hardening flags
		'-fstack-protector*'
		-fstack-clash-protection
		'-fcf-protection=*'
		-fbounds-check -fbounds-checking
		-fno-PIE -fno-pie -nopie -no-pie
		# Spectre mitigations, bug #646076
		'-mindirect-branch=*'
		-mindirect-branch-register
		'-mfunction-return=*'
		-mretpoline

		# Misc
		-fno-unit-at-a-time -fno-strict-overflow

		# Sanitizers
		'-fsanitize*' '-fno-sanitize*'

		# Debugging symbols should generally be very safe to add
		-g '-g[0-9]'
		-ggdb '-ggdb[0-9]'
		-gdwarf '-gdwarf-*'
		-gstabs -gstabs+
		-gz
		-glldb

		# Cosmetic/output related, see e.g. bug #830534
		-fno-diagnostics-color '-fmessage-length=*'
		-fno-ident -fpermissive -frecord-gcc-switches
		-frecord-command-line
		'-fdiagnostics*' '-fplugin*'
		'-W*' -w

		# CPPFLAGS and LDFLAGS
		'-[DUILR]*' '-Wl,*'

		# Linker choice flag
		'-fuse-ld=*'
	)

	# allow a bunch of flags that negate features / control ABI
	ALLOWED_FLAGS+=(
		'-fno-stack-protector*' '-fabi-version=*'
		-fno-strict-aliasing -fno-bounds-check -fno-bounds-checking -fstrict-overflow
		-fno-omit-frame-pointer '-fno-builtin*'
	)
	ALLOWED_FLAGS+=(
		'-mregparm=*' -mno-app-regs -mapp-regs -mno-mmx -mno-sse
		-mno-sse2 -mno-sse3 -mno-ssse3 -mno-sse4 -mno-sse4.1 -mno-sse4.2
		-mno-avx -mno-aes -mno-pclmul -mno-sse4a -mno-3dnow -mno-popcnt
		-mno-abm -mips1 -mips2 -mips3 -mips4 -mips32 -mips64 -mips16 -mplt
		-msoft-float -mno-soft-float -mhard-float -mno-hard-float '-mfpu=*'
		-mieee -mieee-with-inexact '-mschedule=*' -mfloat-gprs -mspe -mno-spe
		-mtls-direct-seg-refs -mno-tls-direct-seg-refs -mflat -mno-flat
		-mno-faster-structs -mfaster-structs -m32 -m64 -mx32 '-mabi=*'
		-mlittle-endian -mbig-endian -EL -EB -fPIC -mlive-g0 '-mcmodel=*'
		-mstack-bias -mno-stack-bias -msecure-plt '-m*-toc' '-mfloat-abi=*'
		-mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400
		-mfix-rm7000 -mno-fix-rm7000 -mfix-r10000 -mno-fix-r10000
		'-mr10k-cache-barrier=*' -mthumb -marm

		# needed for arm64 (and in particular SCS)
		-ffixed-x18

		# gcc 4.5
		-mno-fma4 -mno-movbe -mno-xop -mno-lwp
		# gcc 4.6
		-mno-fsgsbase -mno-rdrnd -mno-f16c -mno-bmi -mno-tbm
		# gcc 4.7
		-mno-avx2 -mno-bmi2 -mno-fma -mno-lzcnt
		# gcc 4.8
		-mno-fxsr -mno-hle -mno-rtm -mno-xsave -mno-xsaveopt
		# gcc 4.9
		-mno-avx512cd -mno-avx512er -mno-avx512f -mno-avx512pf -mno-sha
	)

	# Allow some safe individual flags. Should come along with the bug reference.
	ALLOWED_FLAGS+=(
		# Allow explicit stack realignment to run non-conformant
		# binaries: bug #677852
		-mstackrealign
	)
}

# @FUNCTION: _filter-hardened
# @INTERNAL
# @DESCRIPTION:
# Inverted filters for hardened compiler.  This is trying to unpick
# the hardened compiler defaults.
_filter-hardened() {
	local f
	for f in "$@" ; do
		case "${f}" in
			# Ideally we should only concern ourselves with PIE flags,
			# not -fPIC or -fpic, but too many places filter -fPIC without
			# thinking about -fPIE.
			-fPIC|-fpic|-fPIE|-fpie|-Wl,pie|-pie)
				gcc-specs-pie || continue
				if ! is-flagq -nopie && ! is-flagq -no-pie ; then
					# Support older Gentoo form first (-nopie) before falling
					# back to the official gcc-6+ form (-no-pie).
					if test-flags -nopie >/dev/null ; then
						append-flags -nopie
					else
						append-flags -no-pie
					fi
				fi
				;;
			-fstack-protector)
				gcc-specs-ssp || continue
				is-flagq -fno-stack-protector || append-flags $(test-flags -fno-stack-protector);;
			-fstack-protector-all)
				gcc-specs-ssp-to-all || continue
				is-flagq -fno-stack-protector-all || append-flags $(test-flags -fno-stack-protector-all);;
			-fno-strict-overflow)
				gcc-specs-nostrict || continue
				is-flagq -fstrict-overflow || append-flags $(test-flags -fstrict-overflow);;
		esac
	done
}

# @FUNCTION: _filter-var
# @INTERNAL
# @DESCRIPTION:
# Remove occurrences of strings from variable given in $1
# Strings removed are matched as globs, so for example
# '-O*' would remove -O1, -O2 etc.
_filter-var() {
	local f x var=$1 new=()
	shift

	for f in ${!var} ; do
		for x in "$@" ; do
			# Note this should work with globs like -O*
			[[ ${f} == ${x} ]] && continue 2
		done
		new+=( "${f}" )
	done
	export ${var}="${new[*]}"
}

# @FUNCTION: filter-flags
# @USAGE: <flags>
# @DESCRIPTION:
# Remove particular <flags> from {C,CPP,CXX,CCAS,F,FC,LD}FLAGS.  Accepts shell globs.
filter-flags() {
	_filter-hardened "$@"
	local v
	for v in $(all-flag-vars) ; do
		_filter-var ${v} "$@"
	done
	return 0
}

# @FUNCTION: filter-lfs-flags
# @DESCRIPTION:
# Remove flags that enable Large File Support.
filter-lfs-flags() {
	[[ $# -ne 0 ]] && die "filter-lfs-flags takes no arguments"

	# http://www.gnu.org/s/libc/manual/html_node/Feature-Test-Macros.html
	# _LARGEFILE_SOURCE: enable support for new LFS funcs (ftello/etc...)
	# _LARGEFILE64_SOURCE: enable support for 64bit variants (off64_t/fseeko64/etc...)
	# _FILE_OFFSET_BITS: default to 64bit variants (off_t is defined as off64_t)
	# _TIME_BITS: default to 64bit time_t (requires _FILE_OFFSET_BITS=64)
	filter-flags -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_TIME_BITS=64
}

# @FUNCTION: filter-lto
# @DESCRIPTION:
# Remove flags that enable LTO and those that depend on it
filter-lto() {
	[[ $# -ne 0 ]] && die "filter-lto takes no arguments"
	filter-flags '-flto*' -fwhole-program-vtables '-fsanitize=cfi*'
}

# @FUNCTION: filter-ldflags
# @USAGE: <flags>
# @DESCRIPTION:
# Remove particular <flags> from LDFLAGS.  Accepts shell globs.
filter-ldflags() {
	_filter-var LDFLAGS "$@"
	return 0
}

# @FUNCTION: append-cppflags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to the current CPPFLAGS.
append-cppflags() {
	[[ $# -eq 0 ]] && return 0
	export CPPFLAGS+=" $*"
	return 0
}

# @FUNCTION: append-cflags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to the current CFLAGS.  If a flag might not be supported
# with different compilers (or versions), then use test-flags-CC like so:
# @CODE
# append-cflags $(test-flags-CC -funky-flag)
# @CODE
append-cflags() {
	[[ $# -eq 0 ]] && return 0
	# Do not do automatic flag testing ourselves, bug #417047
	export CFLAGS+=" $*"
	return 0
}

# @FUNCTION: append-cxxflags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to the current CXXFLAGS.  If a flag might not be supported
# with different compilers (or versions), then use test-flags-CXX like so:
# @CODE
# append-cxxflags $(test-flags-CXX -funky-flag)
# @CODE
append-cxxflags() {
	[[ $# -eq 0 ]] && return 0
	# Do not do automatic flag testing ourselves, bug #417047
	export CXXFLAGS+=" $*"
	return 0
}

# @FUNCTION: append-fflags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to the current {F,FC}FLAGS.  If a flag might not be supported
# with different compilers (or versions), then use test-flags-F77 like so:
# @CODE
# append-fflags $(test-flags-F77 -funky-flag)
# @CODE
append-fflags() {
	[[ $# -eq 0 ]] && return 0
	# Do not do automatic flag testing ourselves, bug #417047
	export FFLAGS+=" $*"
	export FCFLAGS+=" $*"
	return 0
}

# @FUNCTION: append-lfs-flags
# @DESCRIPTION:
# Add flags that enable Large File Support.
append-lfs-flags() {
	[[ $# -ne 0 ]] && die "append-lfs-flags takes no arguments"

	# See comments in filter-lfs-flags func for meaning of these
	append-cppflags -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
}

# @FUNCTION: append-ldflags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to the current LDFLAGS.
append-ldflags() {
	[[ $# -eq 0 ]] && return 0
	local flag
	for flag in "$@"; do
		[[ ${flag} == -l* ]] && \
			eqawarn "Appending a library link instruction (${flag}); libraries to link to should not be passed through LDFLAGS"
	done

	export LDFLAGS="${LDFLAGS} $*"
	return 0
}

# @FUNCTION: append-flags
# @USAGE: <flags>
# @DESCRIPTION:
# Add extra <flags> to your current {C,CXX,F,FC}FLAGS.
append-flags() {
	[[ $# -eq 0 ]] && return 0
	case " $* " in
	*' '-[DIU]*) eqawarn 'Please use append-cppflags for preprocessor flags' ;;
	*' '-L*|\
	*' '-Wl,*)  eqawarn 'Please use append-ldflags for linker flags' ;;
	esac
	append-cflags "$@"
	append-cxxflags "$@"
	append-fflags "$@"
	return 0
}

# @FUNCTION: replace-flags
# @USAGE: <old> <new>
# @DESCRIPTION:
# Replace the <old> flag with <new>.  Accepts shell globs for <old>.
replace-flags() {
	[[ $# != 2 ]] && die "Usage: replace-flags <old flag> <new flag>"

	local f var new
	for var in $(all-flag-vars) ; do
		# Looping over the flags instead of using a global
		# substitution ensures that we're working with flag atoms.
		# Otherwise globs like -O* have the potential to wipe out the
		# list of flags.
		new=()
		for f in ${!var} ; do
			# Note this should work with globs like -O*
			[[ ${f} == ${1} ]] && f=${2}
			new+=( "${f}" )
		done
		export ${var}="${new[*]}"
	done

	return 0
}

# @FUNCTION: replace-cpu-flags
# @USAGE: <old> <new>
# @DESCRIPTION:
# Replace cpu flags (like -march/-mcpu/-mtune) that select the <old> cpu
# with flags that select the <new> cpu.  Accepts shell globs for <old>.
replace-cpu-flags() {
	local newcpu="$#" ; newcpu="${!newcpu}"
	while [ $# -gt 1 ] ; do
		# quote to make sure that no globbing is done (particularly on
		# ${oldcpu}) prior to calling replace-flags
		replace-flags "-march=${1}" "-march=${newcpu}"
		replace-flags "-mcpu=${1}" "-mcpu=${newcpu}"
		replace-flags "-mtune=${1}" "-mtune=${newcpu}"
		shift
	done
	return 0
}

# @FUNCTION: _is_flagq
# @USAGE: <variable> <flag>
# @INTERNAL
# @DESCRIPTION:
# Returns shell true if <flag> is in a given <variable>, else returns shell false.
_is_flagq() {
	local x var="$1[*]"
	for x in ${!var} ; do
		[[ ${x} == $2 ]] && return 0
	done
	return 1
}

# @FUNCTION: is-flagq
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is in {C,CXX,F,FC}FLAGS, else returns shell false.  Accepts shell globs.
is-flagq() {
	[[ -n $2 ]] && die "Usage: is-flag <flag>"

	local var
	for var in $(all-flag-vars) ; do
		_is_flagq ${var} "$1" && return 0
	done
	return 1
}

# @FUNCTION: is-flag
# @USAGE: <flag>
# @DESCRIPTION:
# Echo's "true" if flag is set in {C,CXX,F,FC}FLAGS.  Accepts shell globs.
is-flag() {
	is-flagq "$@" && echo true
}

# @FUNCTION: is-ldflagq
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is in LDFLAGS, else returns shell false.  Accepts shell globs.
is-ldflagq() {
	[[ -n $2 ]] && die "Usage: is-ldflag <flag>"
	_is_flagq LDFLAGS $1
}

# @FUNCTION: is-ldflag
# @USAGE: <flag>
# @DESCRIPTION:
# Echo's "true" if flag is set in LDFLAGS.  Accepts shell globs.
is-ldflag() {
	is-ldflagq "$@" && echo true
}

# @FUNCTION: filter-mfpmath
# @USAGE: <math types>
# @DESCRIPTION:
# Remove specified math types from the fpmath flag.  For example, if the user
# has -mfpmath=sse,386, running `filter-mfpmath sse` will leave the user with
# -mfpmath=386.
filter-mfpmath() {
	local orig_mfpmath new_math prune_math

	# save the original -mfpmath flag
	orig_mfpmath=$(get-flag -mfpmath)
	# get the value of the current -mfpmath flag
	new_math=$(get-flag mfpmath)
	# convert "both" to something we can filter
	new_math=${new_math/both/387,sse}
	new_math=" ${new_math//[,+]/ } "
	# figure out which math values are to be removed
	prune_math=""
	for prune_math in "$@" ; do
		new_math=${new_math/ ${prune_math} / }
	done
	new_math=$(echo ${new_math})
	new_math=${new_math// /,}

	if [[ -z ${new_math} ]] ; then
		# if we're removing all user specified math values are
		# slated for removal, then we just filter the flag
		filter-flags ${orig_mfpmath}
	else
		# if we only want to filter some of the user specified
		# math values, then we replace the current flag
		replace-flags ${orig_mfpmath} -mfpmath=${new_math}
	fi
	return 0
}

# @FUNCTION: strip-flags
# @DESCRIPTION:
# Strip *FLAGS of everything except known good/safe flags.  This runs over all
# flags returned by all_flag_vars().
strip-flags() {
	[[ $# -ne 0 ]] && die "strip-flags takes no arguments"
	local x y var

	local ALLOWED_FLAGS
	_setup-allowed-flags

	set -f	# disable pathname expansion

	for var in $(all-flag-vars) ; do
		local new=()

		for x in ${!var} ; do
			for y in "${ALLOWED_FLAGS[@]}" ; do
				if [[ ${x} == ${y} ]] ; then
					new+=( "${x}" )
					break
				fi
			done
		done

		# In case we filtered out all optimization flags fallback to -O2
		if _is_flagq ${var} "-O*" && ! _is_flagq new "-O*" ; then
			new+=( -O2 )
		fi

		if [[ ${!var} != "${new[*]}" ]] ; then
			einfo "strip-flags: ${var}: changed '${!var}' to '${new[*]}'"
		fi
		export ${var}="${new[*]}"
	done

	set +f	# re-enable pathname expansion

	return 0
}

# @FUNCTION: test-flag-PROG
# @USAGE: <compiler> <flag>
# @INTERNAL
# @DESCRIPTION:
# Returns shell true if <flag> is supported by given <compiler>,
# else returns shell false.
test-flag-PROG() {
	[[ ${EAPI} == [67] ]] ||
		die "Internal function ${FUNCNAME} is not available in EAPI ${EAPI}."
	_test-flag-PROG "$@"
}

# @FUNCTION: _test-flag-PROG
# @USAGE: <compiler> <flag>
# @INTERNAL
# @DESCRIPTION:
# Returns shell true if <flag> is supported by given <compiler>,
# else returns shell false.
_test-flag-PROG() {
	local comp=$1
	local lang=$2
	shift 2

	if [[ -z ${comp} ]]; then
		return 1
	fi
	if [[ -z $1 ]]; then
		return 1
	fi

	# verify selected compiler exists before using it
	comp=($(tc-get${comp}))
	# 'comp' can already contain compiler options.
	# 'type' needs a binary name
	if ! type -p ${comp[0]} >/dev/null; then
		return 1
	fi

	# Set up test file.
	local in_src in_ext cmdline_extra=()
	case "${lang}" in
		# compiler/assembler only
		c)
			in_ext='c'
			in_src='int main(void) { return 0; }'
			cmdline_extra+=(-xc -c)
			;;
		c++)
			in_ext='cc'
			in_src='int main(void) { return 0; }'
			cmdline_extra+=(-xc++ -c)
			;;
		f77)
			in_ext='f'
			# fixed source form
			in_src='      end'
			cmdline_extra+=(-xf77 -c)
			;;
		f95)
			in_ext='f90'
			in_src='end'
			cmdline_extra+=(-xf95 -c)
			;;

		# C compiler/assembler/linker
		c+ld)
			in_ext='c'
			in_src='int main(void) { return 0; }'

			if is-ldflagq -fuse-ld=* ; then
				# Respect linker chosen by user so we don't
				# end up giving false results by checking
				# with default linker. bug #832377
				fuse_ld_value=$(get-flag -fuse-ld=*)
				cmdline_extra+=(${fuse_ld_value})
			fi

			cmdline_extra+=(-xc)
			;;
	esac
	local test_in=${T}/test-flag.${in_ext}
	local test_out=${T}/test-flag.exe

	printf "%s\n" "${in_src}" > "${test_in}" || die "Failed to create '${test_in}'"

	# Currently we rely on warning-free output of a compiler
	# before the flag to see if a flag produces any warnings.
	# This has a few drawbacks:
	# - if compiler already generates warnings we filter out
	#   every single flag: bug #712488
	# - if user actually wants to see warnings we just strip
	#   them regardless of warnings type.
	#
	# We can add more selective detection of no-op flags via
	# '-Werror=ignored-optimization-argument' and similar error options
	# or accept unused flags with '-Qunused-arguments' like we
	# used to for bug #627474. Since we now invoke the linker
	# for testing linker flags, unused argument warnings aren't
	# ignored; linker flags may no longer be accepted in CFLAGS.
	#
	# However, warnings emitted by a compiler for a clean source
	# can break feature detection by CMake or autoconf since
	# many checks use -Werror internally. See e.g. bug #714742.
	local cmdline=(
		"${comp[@]}"
		# Clang will warn about unknown gcc flags but exit 0.
		# Need -Werror to force it to exit non-zero.
		#
		# See also bug #712488 and bug #714742.
		-Werror
		"$@"
		# -x<lang> options need to go before first source file
		"${cmdline_extra[@]}"

		"${test_in}" -o "${test_out}"
	)

	"${cmdline[@]}" &>/dev/null
}

# @FUNCTION: test-flag-CC
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is supported by the C compiler, else returns shell false.
test-flag-CC() { _test-flag-PROG CC c "$@"; }

# @FUNCTION: test-flag-CXX
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is supported by the C++ compiler, else returns shell false.
test-flag-CXX() { _test-flag-PROG CXX c++ "$@"; }

# @FUNCTION: test-flag-F77
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is supported by the Fortran 77 compiler, else returns shell false.
test-flag-F77() { _test-flag-PROG F77 f77 "$@"; }

# @FUNCTION: test-flag-FC
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is supported by the Fortran 90 compiler, else returns shell false.
test-flag-FC() { _test-flag-PROG FC f95 "$@"; }

# @FUNCTION: test-flag-CCLD
# @USAGE: <flag>
# @DESCRIPTION:
# Returns shell true if <flag> is supported by the C compiler and linker, else returns shell false.
test-flag-CCLD() { _test-flag-PROG CC c+ld "$@"; }

# @FUNCTION: test-flags-PROG
# @USAGE: <compiler> <flag> [more flags...]
# @INTERNAL
# @DESCRIPTION:
# Returns shell true if <flags> are supported by given <compiler>,
# else returns shell false.
test-flags-PROG() {
	[[ ${EAPI} == [67] ]] ||
		die "Internal function ${FUNCNAME} is not available in EAPI ${EAPI}."
	_test-flags-PROG "$@"
}

# @FUNCTION: _test-flags-PROG
# @USAGE: <compiler> <flag> [more flags...]
# @INTERNAL
# @DESCRIPTION:
# Returns shell true if <flags> are supported by given <compiler>,
# else returns shell false.
_test-flags-PROG() {
	local comp=$1
	local flags=()
	local x

	shift

	[[ -z ${comp} ]] && return 1

	while (( $# )); do
		case "$1" in
			# '-B /foo': bug #687198
			--param|-B)
				if test-flag-${comp} "$1" "$2"; then
					flags+=( "$1" "$2" )
				fi
				shift 2
				;;
			*)
				if test-flag-${comp} "$1"; then
					flags+=( "$1" )
				fi
				shift 1
				;;
		esac
	done

	echo "${flags[*]}"

	# Just bail if we dont have any flags
	[[ ${#flags[@]} -gt 0 ]]
}

# @FUNCTION: test-flags-CC
# @USAGE: <flags>
# @DESCRIPTION:
# Returns shell true if <flags> are supported by the C compiler, else returns shell false.
test-flags-CC() { _test-flags-PROG CC "$@"; }

# @FUNCTION: test-flags-CXX
# @USAGE: <flags>
# @DESCRIPTION:
# Returns shell true if <flags> are supported by the C++ compiler, else returns shell false.
test-flags-CXX() { _test-flags-PROG CXX "$@"; }

# @FUNCTION: test-flags-F77
# @USAGE: <flags>
# @DESCRIPTION:
# Returns shell true if <flags> are supported by the Fortran 77 compiler, else returns shell false.
test-flags-F77() { _test-flags-PROG F77 "$@"; }

# @FUNCTION: test-flags-FC
# @USAGE: <flags>
# @DESCRIPTION:
# Returns shell true if <flags> are supported by the Fortran 90 compiler, else returns shell false.
test-flags-FC() { _test-flags-PROG FC "$@"; }

# @FUNCTION: test-flags-CCLD
# @USAGE: <flags>
# @DESCRIPTION:
# Returns shell true if <flags> are supported by the C compiler and default linker, else returns shell false.
test-flags-CCLD() { _test-flags-PROG CCLD "$@"; }

# @FUNCTION: test-flags
# @USAGE: <flags>
# @DESCRIPTION:
# Short-hand that should hopefully work for both C and C++ compiler, but
# its really only present due to the append-flags() abomination.
test-flags() { test-flags-CC "$@"; }

# @FUNCTION: test_version_info
# @USAGE: <version>
# @DESCRIPTION:
# Returns shell true if the current C compiler version matches <version>, else returns shell false.
# Accepts shell globs.
test_version_info() {
	if [[ $($(tc-getCC) --version 2>&1) == *$1* ]]; then
		return 0
	else
		return 1
	fi
}

# @FUNCTION: strip-unsupported-flags
# @DESCRIPTION:
# Strip {C,CXX,F,FC}FLAGS of any flags not supported by the active toolchain.
strip-unsupported-flags() {
	[[ $# -ne 0 ]] && die "strip-unsupported-flags takes no arguments"
	export CFLAGS=$(test-flags-CC ${CFLAGS})
	export CXXFLAGS=$(test-flags-CXX ${CXXFLAGS})
	export FFLAGS=$(test-flags-F77 ${FFLAGS})
	export FCFLAGS=$(test-flags-FC ${FCFLAGS})
	export LDFLAGS=$(test-flags-CCLD ${LDFLAGS})
}

# @FUNCTION: get-flag
# @USAGE: <flag>
# @DESCRIPTION:
# Find and echo the value for a particular flag.  Accepts shell globs.
get-flag() {
	[[ $# -ne 1 ]] && die "usage: <flag>"
	local f var findflag="$1"

	# this code looks a little flaky but seems to work for
	# everything we want ...
	# for example, if CFLAGS="-march=i686":
	# `get-flag -march` == "-march=i686"
	# `get-flag march` == "i686"
	for var in $(all-flag-vars) ; do
		for f in ${!var} ; do
			if [ "${f/${findflag}}" != "${f}" ] ; then
				printf "%s\n" "${f/-${findflag}=}"
				return 0
			fi
		done
	done
	return 1
}

# @FUNCTION: replace-sparc64-flags
# @DESCRIPTION:
# Sets mcpu to v8 and uses the original value as mtune if none specified.
replace-sparc64-flags() {
	[[ $# -ne 0 ]] && die "replace-sparc64-flags takes no arguments"
	local SPARC64_CPUS="ultrasparc3 ultrasparc v9"

	if [ "${CFLAGS/mtune}" != "${CFLAGS}" ]; then
		for x in ${SPARC64_CPUS}; do
			CFLAGS="${CFLAGS/-mcpu=${x}/-mcpu=v8}"
		done
	else
		for x in ${SPARC64_CPUS}; do
			CFLAGS="${CFLAGS/-mcpu=${x}/-mcpu=v8 -mtune=${x}}"
		done
	fi

	if [ "${CXXFLAGS/mtune}" != "${CXXFLAGS}" ]; then
		for x in ${SPARC64_CPUS}; do
			CXXFLAGS="${CXXFLAGS/-mcpu=${x}/-mcpu=v8}"
		done
	else
		for x in ${SPARC64_CPUS}; do
			CXXFLAGS="${CXXFLAGS/-mcpu=${x}/-mcpu=v8 -mtune=${x}}"
		done
	fi

	export CFLAGS CXXFLAGS
}

# @FUNCTION: append-libs
# @USAGE: <libs>
# @DESCRIPTION:
# Add extra <libs> to the current LIBS. All arguments should be prefixed with
# either -l or -L.  For compatibility, if arguments are not prefixed as
# options, they are given a -l prefix automatically.
append-libs() {
	[[ $# -eq 0 ]] && return 0
	local flag
	for flag in "$@"; do
		if [[ -z "${flag// }" ]]; then
			eqawarn "Appending an empty argument to LIBS is invalid! Skipping."
			continue
		fi
		case $flag in
			-[lL]*)
				export LIBS="${LIBS} ${flag}"
				;;
			-*)
				eqawarn "Appending non-library to LIBS (${flag}); Other linker flags should be passed via LDFLAGS"
				export LIBS="${LIBS} ${flag}"
				;;
			*)
				export LIBS="${LIBS} -l${flag}"
		esac
	done

	return 0
}

# @FUNCTION: raw-ldflags
# @USAGE: [flags]
# @DESCRIPTION:
# Turn C style ldflags (-Wl,-foo) into straight ldflags - the results
# are suitable for passing directly to 'ld'; note LDFLAGS is usually passed
# to gcc where it needs the '-Wl,'.
#
# If no flags are specified, then default to ${LDFLAGS}.
raw-ldflags() {
	local x input="$@"
	[[ -z ${input} ]] && input=${LDFLAGS}
	set --
	for x in ${input} ; do
		case ${x} in
		-Wl,*)
			x=${x#-Wl,}
			set -- "$@" ${x//,/ }
			;;
		*)	# Assume it's a compiler driver flag, so throw it away, bug #441808
			;;
		esac
	done
	echo "$@"
}

# @FUNCTION: no-as-needed
# @RETURN: Flag to disable asneeded behavior for use with append-ldflags.
no-as-needed() {
	[[ $# -ne 0 ]] && die "no-as-needed takes no arguments"
	case $($(tc-getLD) -v 2>&1 </dev/null) in
		*GNU*) # GNU ld
		echo "-Wl,--no-as-needed" ;;
	esac
}

# @FUNCTION: test-compile
# @USAGE: <language> <code>
# @DESCRIPTION:
# Attempts to compile (and possibly link) the given program.  The first
# <language> parameter corresponds to the standard -x compiler argument.
# If the program should additionally be attempted to be linked, the string
# "+ld" should be added to the <language> parameter.
test-compile() {
	local lang=$1
	local code=$2
	shift 2

	[[ -z "${lang}" ]] && return 1
	[[ -z "${code}" ]] && return 1

	local compiler filename_in filename_out args=() libs=()
	case "${lang}" in
		c)
			compiler="$(tc-getCC)"
			filename_in="${T}/test.c"
			filename_out="${T}/test.o"
			args+=(${CFLAGS[@]} -xc -c)
			;;
		c++)
			compiler="$(tc-getCXX)"
			filename_in="${T}/test.cc"
			filename_out="${T}/test.o"
			args+=(${CXXFLAGS[@]} -xc++ -c)
			;;
		f77)
			compiler="$(tc-getF77)"
			filename_in="${T}/test.f"
			filename_out="${T}/test.o"
			args+=(${FFFLAGS[@]} -xf77 -c)
			;;
		f95)
			compiler="$(tc-getFC)"
			filename_in="${T}/test.f90"
			filename_out="${T}/test.o"
			args+=(${FCFLAGS[@]} -xf95 -c)
			;;
		c+ld)
			compiler="$(tc-getCC)"
			filename_in="${T}/test.c"
			filename_out="${T}/test.exe"
			args+=(${CFLAGS[@]} ${LDFLAGS[@]} -xc)
			libs+=(${LIBS[@]})
			;;
		c+++ld)
			compiler="$(tc-getCXX)"
			filename_in="${T}/test.cc"
			filename_out="${T}/test.exe"
			args+=(${CXXFLAGS[@]} ${LDFLAGS[@]} -xc++)
			libs+=(${LIBS[@]})
			;;
		f77+ld)
			compiler="$(tc-getF77)"
			filename_in="${T}/test.f"
			filename_out="${T}/test.exe"
			args+=(${FFLAGS[@]} ${LDFLAGS[@]} -xf77)
			libs+=(${LIBS[@]})
			;;
		f95+ld)
			compiler="$(tc-getFC)"
			filename_in="${T}/test.f90"
			filename_out="${T}/test.exe"
			args+=(${FCFLAGS[@]} ${LDFLAGS[@]} -xf95)
			libs+=(${LIBS[@]})
			;;
		*)
			die "Unknown compiled language ${lang}"
			;;
	esac

	printf "%s\n" "${code}" > "${filename_in}" || die "Failed to create '${test_in}'"

	"${compiler}" ${args[@]} "${filename_in}" -o "${filename_out}" ${libs[@]} &>/dev/null
}

# @FUNCTION: append-atomic-flags
# @USAGE: [bytes]
# @DESCRIPTION:
# Attempts to detect if appending -latomic is required to use
# a specific-sized atomic intrinsic, and if so, appends it.  If the bytesize
# is not specified, then check the four most common byte sizes (1, 2, 4, 8).
# >=16-byte atomics are not included in this default set and must be explicitly
# passed if required.  This may require you to add a macro definition like
# -Duint128_t=__uint128_t to your CFLAGS.
append-atomic-flags() {
	# this implementation is as described in bug #820101
	local code

	# first, ensure we can compile a trivial program
	# this is because we can't distinguish if test-compile
	# fails because -latomic is actually needed or if we have a
	# broken toolchain (like due to bad FLAGS)
	read -r -d '' code <<- EOF
		int main(void)
		{
			return 0;
		}
	EOF

	# if toolchain is broken, just return silently.  it's better to
	# let other pieces of the build fail later down the line than to
	# make people think that something to do with atomic support is the
	# cause of their problems.
	test-compile "c+ld" "${code}" || return

	local bytesizes
	[[ "${#}" == "0" ]] && bytesizes=( "1" "2" "4" "8" ) || bytesizes="${@}"

	for bytesize in ${bytesizes[@]}
	do
		# this sample program is informed by the great testing from the buildroot project:
		# https://github.com/buildroot/buildroot/commit/6856e417da4f3aa77e2a814db2a89429af072f7d
		read -r -d '' code <<- EOF
			#include <stdint.h>
			int main(void)
			{
				uint$((${bytesize} * 8))_t a = 0;
				__atomic_add_fetch(&a, 3, __ATOMIC_RELAXED);
				__atomic_compare_exchange_n(&a, &a, 2, 1, __ATOMIC_RELAXED, __ATOMIC_RELAXED);
				return 0;
			}
		EOF

		# do nothing if test program links fine
		test-compile "c+ld" "${code}" && continue

		# ensure that the toolchain supports -latomic
		test-flags-CCLD "-latomic" &>/dev/null || die "-latomic is required but not supported by $(tc-getCC)"

		append-libs "-latomic"

		# verify that this did indeed fix the problem
		test-compile "c+ld" "${code}" || \
			die "libatomic does not include an implementation of ${bytesize}-byte atomics for this toolchain"

		# if any of the required bytesizes require -latomic, no need to continue
		# checking the others
		return
	done
}

fi