1; Options for the Fortran front end. 2; Copyright (C) 2003-2019 Free Software Foundation, Inc. 3; 4; This file is part of GCC. 5; 6; GCC is free software; you can redistribute it and/or modify it under 7; the terms of the GNU General Public License as published by the Free 8; Software Foundation; either version 3, or (at your option) any later 9; version. 10; 11; GCC is distributed in the hope that it will be useful, but WITHOUT ANY 12; WARRANTY; without even the implied warranty of MERCHANTABILITY or 13; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14; for more details. 15; 16; You should have received a copy of the GNU General Public License 17; along with GCC; see the file COPYING3. If not see 18; <http://www.gnu.org/licenses/>. 19 20; See the GCC internals manual for a description of this file's format. 21 22; Please try to keep this file in ASCII collating order. 23 24Language 25Fortran 26 27-all-warnings 28Fortran Alias(Wall) 29 30-assert 31Fortran Separate Alias(A) 32 33-assert= 34Fortran Joined Alias(A) 35 36-comments 37Fortran Alias(C) 38 39-comments-in-macros 40Fortran Alias(CC) 41 42-define-macro 43Fortran Separate Alias(D) 44 45-define-macro= 46Fortran Joined Alias(D) 47 48-dependencies 49Fortran Alias(M) 50 51-dump 52Fortran Separate Alias(d) 53 54-dump= 55Fortran Joined Alias(d) 56 57-include-barrier 58Fortran Alias(I, -) 59 60-include-directory 61Fortran Separate Alias(I) 62 63-include-directory= 64Fortran Joined Alias(I) 65 66-include-directory-after 67Fortran Separate Alias(idirafter) 68 69-include-directory-after= 70Fortran Joined Alias(idirafter) 71 72-include-prefix 73Fortran Separate Alias(iprefix) 74 75-include-prefix= 76Fortran JoinedOrMissing Alias(iprefix) 77 78-no-line-commands 79Fortran Alias(P) 80 81-no-standard-includes 82Fortran Alias(nostdinc) 83 84-output 85Fortran Separate Alias(o) 86 87-output= 88Fortran Joined Alias(o) 89 90-preprocess 91Fortran Undocumented Alias(E) 92 93-print-missing-file-dependencies 94Fortran Alias(MG) 95 96-trace-includes 97Fortran Alias(H) 98 99-undefine-macro 100Fortran Separate Alias(U) 101 102-undefine-macro= 103Fortran Joined Alias(U) 104 105-user-dependencies 106Fortran Alias(MM) 107 108-verbose 109Fortran Alias(v) 110 111-write-dependencies 112Fortran NoDriverArg Separate Alias(MD) 113 114-write-user-dependencies 115Fortran NoDriverArg Separate Alias(MMD) 116 117A 118Fortran Joined Separate 119; Documented in C 120 121C 122Fortran 123; Documented in C 124 125CC 126Fortran 127; Documented in C 128 129D 130Fortran Joined Separate 131; Documented in C 132 133E 134Fortran Undocumented 135 136H 137Fortran 138; Documented in C 139 140I 141Fortran Joined Separate 142; Documented in C 143 144J 145Fortran Joined Separate 146-J<directory> Put MODULE files in 'directory'. 147 148M 149Fortran 150; Documented in C 151 152MD 153Fortran Separate NoDriverArg 154; Documented in C 155 156MF 157Fortran Joined Separate 158; Documented in C 159 160MG 161Fortran 162; Documented in C 163 164MM 165Fortran 166; Documented in C 167 168MMD 169Fortran Separate NoDriverArg 170; Documented in C 171 172MP 173Fortran 174; Documented in C 175 176MT 177Fortran Joined Separate 178; Documented in C 179 180MQ 181Fortran Joined Separate 182; Documented in C 183 184P 185Fortran 186; Documented in C 187 188U 189Fortran Joined Separate 190; Documented in C 191 192Wall 193Fortran 194; Documented in C 195 196Waliasing 197Fortran Warning Var(warn_aliasing) LangEnabledBy(Fortran,Wall) 198Warn about possible aliasing of dummy arguments. 199 200Walign-commons 201Fortran Warning Var(warn_align_commons) Init(1) 202Warn about alignment of COMMON blocks. 203 204Wampersand 205Fortran Warning Var(warn_ampersand) LangEnabledBy(Fortran,Wall || Wpedantic) 206Warn about missing ampersand in continued character constants. 207 208Warray-temporaries 209Fortran Warning Var(warn_array_temporaries) 210Warn about creation of array temporaries. 211 212Wargument-mismatch 213Fortran Warning Var(warn_argument_mismatch) Init(1) 214Warn about type and rank mismatches between arguments and parameters. 215 216Wc-binding-type 217Fortran Var(warn_c_binding_type) Warning LangEnabledBy(Fortran,Wall) 218Warn if the type of a variable might be not interoperable with C. 219 220Wdate-time 221Fortran 222; Documented in C 223 224Wcharacter-truncation 225Fortran Var(warn_character_truncation) Warning LangEnabledBy(Fortran,Wall) 226Warn about truncated character expressions. 227 228Wcompare-reals 229Fortran Warning Var(warn_compare_reals) LangEnabledBy(Fortran,Wextra) 230Warn about equality comparisons involving REAL or COMPLEX expressions. 231 232Wconversion 233Fortran Var(warn_conversion) Warning LangEnabledBy(Fortran,Wall) 234; Documented in C 235 236Wconversion-extra 237Fortran Var(warn_conversion_extra) Warning 238Warn about most implicit conversions. 239 240Wdo-subscript 241Fortran Var(warn_do_subscript) Warning LangEnabledBy(Fortran,Wextra) 242Warn about possibly incorrect subscripts in do loops. 243 244Wextra 245Fortran Warning 246; Documented in common 247 248Wfrontend-loop-interchange 249Fortran Var(flag_warn_frontend_loop_interchange) 250Warn if loops have been interchanged. 251 252Wfunction-elimination 253Fortran Warning Var(warn_function_elimination) LangEnabledBy(Fortran,Wextra) 254Warn about function call elimination. 255 256Wimplicit-interface 257Fortran Warning Var(warn_implicit_interface) 258Warn about calls with implicit interface. 259 260Wimplicit-procedure 261Fortran Warning Var(warn_implicit_procedure) 262Warn about called procedures not explicitly declared. 263 264Winteger-division 265Fortran Warning Var(warn_integer_division) LangEnabledBy(Fortran,Wall) 266Warn about constant integer divisions with truncated results. 267 268Wline-truncation 269Fortran Warning Var(warn_line_truncation) LangEnabledBy(Fortran,Wall) Init(-1) 270Warn about truncated source lines. 271 272Wintrinsics-std 273Fortran Var(warn_intrinsics_std) Warning LangEnabledBy(Fortran,Wall) 274Warn on intrinsics not part of the selected standard. 275 276Wmaybe-uninitialized 277Fortran LangEnabledBy(Fortran,Wall) 278; Documented in common.opt 279 280Wmissing-include-dirs 281Fortran 282; Documented in C/C++ 283 284Wuse-without-only 285Fortran Var(warn_use_without_only) Warning 286Warn about USE statements that have no ONLY qualifier. 287 288Wopenmp-simd 289Fortran 290; Documented in C 291 292Wpedantic 293Fortran 294; Documented in common.opt 295 296Wreal-q-constant 297Fortran Warning Var(warn_real_q_constant) LangEnabledBy(Fortran,Wall) 298Warn about real-literal-constants with 'q' exponent-letter. 299 300Wrealloc-lhs 301Fortran Warning Var(warn_realloc_lhs) LangEnabledBy(Fortran,Wrealloc-lhs-all) 302Warn when a left-hand-side array variable is reallocated. 303 304Wrealloc-lhs-all 305Fortran Warning Var(warn_realloc_lhs_all) 306Warn when a left-hand-side variable is reallocated. 307 308Wtarget-lifetime 309Fortran Warning Var(warn_target_lifetime) LangEnabledBy(Fortran,Wall) 310Warn if the pointer in a pointer assignment might outlive its target. 311 312Wreturn-type 313Fortran Warning LangEnabledBy(Fortran,Wall) 314; Documented in C 315 316Wsurprising 317Fortran Warning Var(warn_surprising) LangEnabledBy(Fortran,Wall) 318Warn about \"suspicious\" constructs. 319 320Wtabs 321Fortran Warning Var(warn_tabs) LangEnabledBy(Fortran,Wall || Wpedantic) 322Permit nonconforming uses of the tab character. 323 324Wundefined-do-loop 325Fortran Warning Var(warn_undefined_do_loop) LangEnabledBy(Fortran,Wall) 326Warn about an invalid DO loop. 327 328Wunderflow 329Fortran Warning Var(warn_underflow) Init(1) 330Warn about underflow of numerical constant expressions. 331 332Wuninitialized 333Fortran LangEnabledBy(Fortran,Wall) 334; Documented in common.opt 335 336Wintrinsic-shadow 337Fortran Warning Var(warn_intrinsic_shadow) LangEnabledBy(Fortran,Wall) 338Warn if a user-procedure has the same name as an intrinsic. 339 340Wunused 341LangEnabledBy(Fortran,Wall) 342; Documented in common.opt 343 344Wunused-dummy-argument 345Fortran Warning Var(warn_unused_dummy_argument) LangEnabledBy(Fortran,Wall) 346Warn about unused dummy arguments. 347 348Wzerotrip 349Fortran Warning Var(warn_zerotrip) LangEnabledBy(Fortran,Wall) 350Warn about zero-trip DO loops. 351 352cpp 353Fortran Negative(nocpp) 354Enable preprocessing. 355 356cpp= 357Fortran Joined Negative(nocpp) Undocumented NoDWARFRecord 358; Internal option generated by specs from -cpp. 359 360nocpp 361Fortran Negative(cpp) 362Disable preprocessing. 363 364d 365Fortran Joined 366; Documented in common.opt 367 368faggressive-function-elimination 369Fortran Var(flag_aggressive_function_elimination) 370Eliminate multiple function invocations also for impure functions. 371 372falign-commons 373Fortran Var(flag_align_commons) Init(1) 374Enable alignment of COMMON blocks. 375 376fall-intrinsics 377Fortran RejectNegative Var(flag_all_intrinsics) 378All intrinsics procedures are available regardless of selected standard. 379 380fallow-leading-underscore 381Fortran Undocumented Var(flag_allow_leading_underscore) 382; For internal use only: allow the first character of symbol names to be an underscore 383 384fautomatic 385Fortran Var(flag_automatic) Init(1) 386Do not treat local variables and COMMON blocks as if they were named in SAVE statements. 387 388fbackslash 389Fortran Var(flag_backslash) 390Specify that backslash in string introduces an escape character. 391 392fbacktrace 393Fortran Var(flag_backtrace) Init(1) 394Produce a backtrace when a runtime error is encountered. 395 396fblas-matmul-limit= 397Fortran RejectNegative Joined UInteger Var(flag_blas_matmul_limit) Init(30) 398-fblas-matmul-limit=<n> Size of the smallest matrix for which matmul will use BLAS. 399 400fcheck-array-temporaries 401Fortran 402Produce a warning at runtime if a array temporary has been created for a procedure argument. 403 404fconvert= 405Fortran RejectNegative Joined Enum(gfc_convert) Var(flag_convert) Init(GFC_FLAG_CONVERT_NATIVE) 406-fconvert=<big-endian|little-endian|native|swap> The endianness used for unformatted files. 407 408Enum 409Name(gfc_convert) Type(enum gfc_convert) UnknownError(Unrecognized option to endianness value: %qs) 410 411EnumValue 412Enum(gfc_convert) String(big-endian) Value(GFC_FLAG_CONVERT_BIG) 413 414EnumValue 415Enum(gfc_convert) String(little-endian) Value(GFC_FLAG_CONVERT_LITTLE) 416 417EnumValue 418Enum(gfc_convert) String(native) Value(GFC_FLAG_CONVERT_NATIVE) 419 420EnumValue 421Enum(gfc_convert) String(swap) Value(GFC_FLAG_CONVERT_SWAP) 422 423fcray-pointer 424Fortran Var(flag_cray_pointer) 425Use the Cray Pointer extension. 426 427fc-prototypes 428Fortran Var(flag_c_prototypes) 429Generate C prototypes from BIND(C) declarations. 430 431fc-prototypes-external 432Fortran Var(flag_c_prototypes_external) 433Generate C prototypes from non-BIND(C) external procedure definitions. 434 435fd-lines-as-code 436Fortran RejectNegative 437Ignore 'D' in column one in fixed form. 438 439fd-lines-as-comments 440Fortran RejectNegative 441Treat lines with 'D' in column one as comments. 442 443fdec 444Fortran Var(flag_dec) 445Enable all DEC language extensions. 446 447fdec-include 448Fortran Var(flag_dec_include) 449Enable legacy parsing of INCLUDE as statement. 450 451fdec-intrinsic-ints 452Fortran Var(flag_dec_intrinsic_ints) 453Enable kind-specific variants of integer intrinsic functions. 454 455fdec-math 456Fortran Var(flag_dec_math) 457Enable legacy math intrinsics for compatibility. 458 459fdec-structure 460Fortran Var(flag_dec_structure) 461Enable support for DEC STRUCTURE/RECORD. 462 463fdec-static 464Fortran Var(flag_dec_static) 465Enable DEC-style STATIC and AUTOMATIC attributes. 466 467fdefault-double-8 468Fortran Var(flag_default_double) 469Set the default double precision kind to an 8 byte wide type. 470 471fdefault-integer-8 472Fortran Var(flag_default_integer) 473Set the default integer kind to an 8 byte wide type. 474 475fdefault-real-8 476Fortran Var(flag_default_real_8) 477Set the default real kind to an 8 byte wide type. 478 479fdefault-real-10 480Fortran Var(flag_default_real_10) 481Set the default real kind to an 10 byte wide type. 482 483fdefault-real-16 484Fortran Var(flag_default_real_16) 485Set the default real kind to an 16 byte wide type. 486 487fdollar-ok 488Fortran Var(flag_dollar_ok) 489Allow dollar signs in entity names. 490 491fdump-core 492Fortran Ignore 493Does nothing. Preserved for backward compatibility. 494 495fdump-fortran-original 496Fortran Var(flag_dump_fortran_original) 497Display the code tree after parsing. 498 499fdump-fortran-optimized 500Fortran Var(flag_dump_fortran_optimized) 501Display the code tree after front end optimization. 502 503fdump-fortran-global 504Fortran Var(flag_dump_fortran_global) 505Display the global symbol table after parsing. 506 507fdump-parse-tree 508Fortran Alias(fdump-fortran-original) 509Display the code tree after parsing; deprecated option. 510 511fexternal-blas 512Fortran Var(flag_external_blas) 513Specify that an external BLAS library should be used for matmul calls on large-size arrays. 514 515ff2c 516Fortran Var(flag_f2c) 517Use f2c calling convention. 518 519ffixed-form 520Fortran RejectNegative 521Assume that the source file is fixed form. 522 523ftest-forall-temp 524Fortran Var(flag_test_forall_temp) Init(0) 525Force creation of temporary to test infrequently-executed forall code. 526 527finteger-4-integer-8 528Fortran RejectNegative Var(flag_integer4_kind,8) 529Interpret any INTEGER(4) as an INTEGER(8). 530 531fintrinsic-modules-path 532Fortran RejectNegative Separate 533Specify where to find the compiled intrinsic modules. 534 535fintrinsic-modules-path= 536Fortran RejectNegative Joined 537Specify where to find the compiled intrinsic modules. 538 539ffixed-line-length-none 540Fortran RejectNegative Var(flag_fixed_line_length,0) 541Allow arbitrary character line width in fixed mode. 542 543ffixed-line-length- 544Fortran RejectNegative Joined UInteger Var(flag_fixed_line_length) Init(72) 545-ffixed-line-length-<n> Use n as character line width in fixed mode. 546 547fpad-source 548Fortran Var(flag_pad_source) Init(1) 549Pad shorter fixed form lines to line width with spaces. 550 551ffpe-trap= 552Fortran RejectNegative JoinedOrMissing 553-ffpe-trap=[...] Stop on following floating point exceptions. 554 555ffpe-summary= 556Fortran RejectNegative JoinedOrMissing 557-ffpe-summary=[...] Print summary of floating point exceptions. 558 559ffree-form 560Fortran RejectNegative 561Assume that the source file is free form. 562 563ffree-line-length-none 564Fortran RejectNegative Var(flag_free_line_length,0) 565Allow arbitrary character line width in free mode. 566 567ffree-line-length- 568Fortran RejectNegative Joined UInteger Var(flag_free_line_length) Init(132) 569-ffree-line-length-<n> Use n as character line width in free mode. 570 571ffrontend-loop-interchange 572Fortran Var(flag_frontend_loop_interchange) Init(-1) 573Try to interchange loops if profitable. 574 575ffrontend-optimize 576Fortran Var(flag_frontend_optimize) Init(-1) 577Enable front end optimization. 578 579fimplicit-none 580Fortran Var(flag_implicit_none) 581Specify that no implicit typing is allowed, unless overridden by explicit IMPLICIT statements. 582 583finit-character= 584Fortran RejectNegative Joined UInteger 585-finit-character=<n> Initialize local character variables to ASCII value n. 586 587finit-derived 588Fortran Var(flag_init_derived) 589Initialize components of derived type variables according to other init flags. 590 591finit-integer= 592Fortran RejectNegative Joined 593-finit-integer=<n> Initialize local integer variables to n. 594 595finit-local-zero 596Fortran 597Initialize local variables to zero (from g77). 598 599finit-logical= 600Fortran RejectNegative Joined 601-finit-logical=<true|false> Initialize local logical variables. 602 603finit-real= 604Fortran RejectNegative ToLower Joined Enum(gfc_init_local_real) Var(flag_init_real) Init(GFC_INIT_REAL_OFF) 605-finit-real=<zero|snan|nan|inf|-inf> Initialize local real variables. 606 607Enum 608Name(gfc_init_local_real) Type(enum gfc_init_local_real) UnknownError(Unrecognized option to floating-point init value: %qs) 609 610EnumValue 611Enum(gfc_init_local_real) String(zero) Value(GFC_INIT_REAL_ZERO) 612 613EnumValue 614Enum(gfc_init_local_real) String(snan) Value(GFC_INIT_REAL_SNAN) 615 616EnumValue 617Enum(gfc_init_local_real) String(nan) Value(GFC_INIT_REAL_NAN) 618 619EnumValue 620Enum(gfc_init_local_real) String(inf) Value(GFC_INIT_REAL_INF) 621 622EnumValue 623Enum(gfc_init_local_real) String(-inf) Value(GFC_INIT_REAL_NEG_INF) 624 625finline-matmul-limit= 626Fortran RejectNegative Joined UInteger Var(flag_inline_matmul_limit) Init(-1) 627-finline-matmul-limit=<n> Specify the size of the largest matrix for which matmul will be inlined. 628 629fmax-array-constructor= 630Fortran RejectNegative Joined UInteger Var(flag_max_array_constructor) Init(65535) 631-fmax-array-constructor=<n> Maximum number of objects in an array constructor. 632 633fmax-identifier-length= 634Fortran RejectNegative Joined UInteger 635-fmax-identifier-length=<n> Maximum identifier length. 636 637fmax-subrecord-length= 638Fortran RejectNegative Joined UInteger Var(flag_max_subrecord_length) 639-fmax-subrecord-length=<n> Maximum length for subrecords. 640 641fmax-stack-var-size= 642Fortran RejectNegative Joined UInteger Var(flag_max_stack_var_size) Init(-2) 643-fmax-stack-var-size=<n> Size in bytes of the largest array that will be put on the stack. 644 645fstack-arrays 646Fortran Var(flag_stack_arrays) Init(-1) 647Put all local arrays on stack. 648 649fmodule-private 650Fortran Var(flag_module_private) 651Set default accessibility of module entities to PRIVATE. 652 653fopenacc 654Fortran LTO 655; Documented in C 656 657fopenacc-dim= 658Fortran LTO Joined Var(flag_openacc_dims) 659; Documented in C 660 661fopenmp 662Fortran LTO 663; Documented in C 664 665fopenmp-simd 666Fortran 667; Documented in C 668 669fpack-derived 670Fortran Var(flag_pack_derived) 671Try to lay out derived types as compactly as possible. 672 673fpreprocessed 674Fortran 675; Documented in C 676 677fprotect-parens 678Fortran Var(flag_protect_parens) Init(-1) 679Protect parentheses in expressions. 680 681fpre-include= 682Fortran RejectNegative Joined Var(flag_pre_include) Undocumented 683Path to header file that should be pre-included before each compilation unit. 684 685frange-check 686Fortran Var(flag_range_check) Init(1) 687Enable range checking during compilation. 688 689freal-4-real-8 690Fortran RejectNegative Var(flag_real4_kind,8) 691Interpret any REAL(4) as a REAL(8). 692 693freal-4-real-10 694Fortran RejectNegative Var(flag_real4_kind,10) 695Interpret any REAL(4) as a REAL(10). 696 697freal-4-real-16 698Fortran RejectNegative Var(flag_real4_kind,16) 699Interpret any REAL(4) as a REAL(16). 700 701freal-8-real-4 702Fortran RejectNegative Var(flag_real8_kind,4) 703Interpret any REAL(8) as a REAL(4). 704 705freal-8-real-10 706Fortran RejectNegative Var(flag_real8_kind,10) 707Interpret any REAL(8) as a REAL(10). 708 709freal-8-real-16 710Fortran RejectNegative Var(flag_real8_kind,16) 711Interpret any REAL(8) as a REAL(16). 712 713frealloc-lhs 714Fortran Var(flag_realloc_lhs) Init(-1) 715Reallocate the LHS in assignments. 716 717frecord-marker=4 718Fortran RejectNegative Var(flag_record_marker,4) 719Use a 4-byte record marker for unformatted files. 720 721frecord-marker=8 722Fortran RejectNegative Var(flag_record_marker,8) 723Use an 8-byte record marker for unformatted files. 724 725frecursive 726Fortran Var(flag_recursive) 727Allocate local variables on the stack to allow indirect recursion. 728 729frepack-arrays 730Fortran Var(flag_repack_arrays) 731Copy array sections into a contiguous block on procedure entry. 732 733fcoarray= 734Fortran RejectNegative Joined Enum(gfc_fcoarray) Var(flag_coarray) Init(GFC_FCOARRAY_NONE) 735-fcoarray=<none|single|lib> Specify which coarray parallelization should be used. 736 737Enum 738Name(gfc_fcoarray) Type(enum gfc_fcoarray) UnknownError(Unrecognized option: %qs) 739 740EnumValue 741Enum(gfc_fcoarray) String(none) Value(GFC_FCOARRAY_NONE) 742 743EnumValue 744Enum(gfc_fcoarray) String(single) Value(GFC_FCOARRAY_SINGLE) 745 746EnumValue 747Enum(gfc_fcoarray) String(lib) Value(GFC_FCOARRAY_LIB) 748 749fcheck= 750Fortran RejectNegative JoinedOrMissing 751-fcheck=[...] Specify which runtime checks are to be performed. 752 753fsecond-underscore 754Fortran Var(flag_second_underscore) Init(-1) 755Append a second underscore if the name already contains an underscore. 756 757fshort-enums 758Fortran Var(flag_short_enums) 759; Documented in C 760 761fsign-zero 762Fortran Var(flag_sign_zero) Init(1) 763Apply negative sign to zero values. 764 765ftail-call-workaround 766Fortran Alias(ftail-call-workaround=,1,0) 767 768ftail-call-workaround= 769Fortran RejectNegative Joined UInteger IntegerRange(0, 2) Var(flag_tail_call_workaround) Init(1) 770Disallow tail call optimization when a calling routine may have omitted character lengths. 771 772funderscoring 773Fortran Var(flag_underscoring) Init(1) 774Append underscores to externally visible names. 775 776fwhole-file 777Fortran Ignore 778Does nothing. Preserved for backward compatibility. 779 780fworking-directory 781Fortran 782; Documented in C 783 784idirafter 785Fortran Joined Separate 786; Documented in C 787 788imultilib 789Fortran Joined Separate 790; Documented in C 791 792iprefix 793Fortran Joined Separate 794; Documented in C 795 796iquote 797Fortran Joined Separate 798; Documented in C 799 800isysroot 801Fortran Joined Separate 802; Documented in C 803 804isystem 805Fortran Joined Separate 806; Documented in C 807 808nostdinc 809Fortran 810; Documented in C 811 812o 813Fortran Joined Separate 814; Documented in common.opt 815 816static-libgfortran 817Fortran 818Statically link the GNU Fortran helper library (libgfortran). 819 820std=f2003 821Fortran 822Conform to the ISO Fortran 2003 standard. 823 824std=f2008 825Fortran 826Conform to the ISO Fortran 2008 standard. 827 828std=f2008ts 829Fortran 830Conform to the ISO Fortran 2008 standard including TS 29113. 831 832std=f2018 833Fortran 834Conform to the ISO Fortran 2018 standard. 835 836std=f95 837Fortran 838Conform to the ISO Fortran 95 standard. 839 840std=gnu 841Fortran 842Conform to nothing in particular. 843 844std=legacy 845Fortran 846Accept extensions to support legacy code. 847 848undef 849Fortran 850; Documented in C 851 852v 853Fortran 854; Documented in C 855 856; This comment is to ensure we retain the blank line above. 857