Shamusworld >> Repos - rmac/blob - procln.c

   1 //
   2 // RMAC - Reboot's Macro Assembler for the Atari Jaguar Console System
   3 // PROCLN.C - Line Processing
   4 // Copyright (C) 199x Landon Dyer, 2011 Reboot and Friends
   5 // RMAC derived from MADMAC v1.07 Written by Landon Dyer, 1986
   6 // Source Utilised with the Kind Permission of Landon Dyer
   7 //
   8
   9 #include "procln.h"
  10 #include "listing.h"
  11 #include "amode.h"
  12 #include "error.h"
  13 #include "sect.h"
  14 #include "expr.h"
  15 #include "mach.h"
  16 #include "direct.h"
  17 #include "macro.h"
  18 #include "symbol.h"
  19 #include "risca.h"
  20
  21 #define DEF_KW                                  // Declare keyword values
  22 #include "kwtab.h"                              // Incl generated keyword tables & defs
  23
  24 #define DEF_MN                                  // Incl 68k keyword definitions
  25 #define DECL_MN                                 // Incl 68k keyword state machine tables
  26 #include "mntab.h"
  27
  28 #define DEF_MR
  29 #define DECL_MR
  30 #include "risckw.h"
  31
  32 IFENT * ifent;                                  // Current ifent
  33 static IFENT ifent0;                    // Root ifent
  34 static IFENT * f_ifent;                 // Freelist of ifents
  35 static int disabled;                    // Assembly conditionally disabled
  36 int just_bss;                                   // 1, ds.b in microprocessor mode
  37 VALUE pcloc;                                    // Value of "PC" at beginning of line
  38 IFENT * ifent;                                  // Current ifent
  39 SYM * lab_sym;                                  // Label on line (or NULL)
  40
  41 char extra_stuff[] = "extra (unexpected) text found after addressing mode";
  42 char * comma_error = "missing comma";
  43 char * syntax_error = "syntax error";
  44 char * locgl_error = "cannot GLOBL local symbol";
  45 char * lab_ignored = "label ignored";
  46
  47 // Table to convert an addressing-mode number to a bitmask.
  48 LONG amsktab[0112] = {
  49         M_DREG, M_DREG, M_DREG, M_DREG,
  50         M_DREG, M_DREG, M_DREG, M_DREG,
  51
  52         M_AREG, M_AREG, M_AREG, M_AREG,
  53         M_AREG, M_AREG, M_AREG, M_AREG,
  54
  55         M_AIND, M_AIND, M_AIND, M_AIND,
  56         M_AIND, M_AIND, M_AIND, M_AIND,
  57
  58         M_APOSTINC, M_APOSTINC, M_APOSTINC, M_APOSTINC,
  59         M_APOSTINC, M_APOSTINC, M_APOSTINC, M_APOSTINC,
  60
  61         M_APREDEC, M_APREDEC, M_APREDEC, M_APREDEC,
  62         M_APREDEC, M_APREDEC, M_APREDEC, M_APREDEC,
  63
  64         M_ADISP, M_ADISP, M_ADISP, M_ADISP,
  65         M_ADISP, M_ADISP, M_ADISP, M_ADISP,
  66
  67         M_AINDEXED, M_AINDEXED, M_AINDEXED, M_AINDEXED,
  68         M_AINDEXED, M_AINDEXED, M_AINDEXED, M_AINDEXED,
  69
  70         M_ABSW,                                                                                 // 070
  71         M_ABSL,                                                                                 // 071
  72         M_PCDISP,                                                                               // 072
  73         M_PCINDEXED,                                                                    // 073
  74         M_IMMED,                                                                                // 074
  75         0L,                                                                                             // 075
  76         0L,                                                                                             // 076
  77         0L,                                                                                             // 077
  78         M_ABASE,                                                                                // 0100
  79         M_MEMPOST,                                                                              // 0101
  80         M_MEMPRE,                                                                               // 0102
  81         M_PCBASE,                                                                               // 0103
  82         M_PCMPOST,                                                                              // 0104
  83         M_PCMPRE,                                                                               // 0105
  84         M_AM_USP,                                                                               // 0106
  85         M_AM_SR,                                                                                // 0107
  86         M_AM_CCR,                                                                               // 0110
  87         M_AM_NONE                                                                               // 0111
  88 };                                                                                                      // 0112 length
  89
  90
  91 //
  92 // Initialize Line Processor
  93 //
  94 void init_procln(void)
  95 {
  96         disabled = 0;
  97         ifent = &ifent0;
  98         f_ifent = ifent0.if_prev = NULL;
  99         ifent0.if_state = 0;
 100 }
 101
 102
 103 //
 104 // Line Processor
 105 //
 106 void assemble(void)
 107 {
 108         int state;                                      // Keyword machine state (output)
 109         int j;                                          // Random int, must be fast
 110         char * p;                                       // Random char ptr, must be fast
 111         TOKEN * tk;                                     // First token in line
 112         char * label;                           // Symbol (or NULL)
 113         char * equate;                          // Symbol (or NULL)
 114         int labtyp = 0;                         // Label type (':', DCOLON)
 115         int equtyp = 0;                         // Equ type ('=', DEQUALS)
 116         VALUE eval;                                     // Expression value
 117         WORD eattr;                                     // Expression attributes
 118         SYM * esym;                                     // External symbol involved in expr.
 119         WORD siz = 0;                           // Size suffix to mnem/diretve/macro
 120         LONG amsk0, amsk1;                      // Address-type masks for ea0, ea1
 121         MNTAB * m;                                      // Code generation table pointer
 122         SYM * sy, * sy2;                        // Symbol (temp usage)
 123         char * opname = NULL;           // Name of dirctve/mnemonic/macro
 124         int listflag;                           // 0: Don't call listeol()
 125         int as68mode = 0;                       // 1: Handle multiple labels
 126         WORD rmask;                                     // Register list, for REG
 127         int registerbank;                       // RISC register bank
 128         int riscreg;                            // RISC register
 129
 130         listflag = 0;                           // Initialise listing flag
 131
 132 loop:                                                   // Line processing loop label
 133
 134         // Get another line of tokens
 135         if (tokln() == TKEOF)
 136         {
 137                 if (list_flag && listflag)                      // Flush last line of source
 138                         listeol();
 139
 140                 if (ifent->if_prev != NULL)                     // Check conditional token
 141                         error("hit EOF without finding matching .endif");
 142
 143                 return;
 144         }
 145
 146         DEBUG DumpTokenBuffer();
 147
 148         if (list_flag)
 149         {
 150                 if (listflag && listing > 0)
 151                         listeol();                                              // Tell listing generator about EOL
 152
 153                 lstout((char)(disabled ? '-' : lntag)); // Prepare new line for listing
 154                 listflag = 1;                                           // OK to call `listeol' now
 155                 just_bss = 0;                                           // Reset just_bss mode
 156         }
 157
 158         state = -3;                                                             // No keyword (just EOL)
 159         label = NULL;                                                   // No label
 160         lab_sym = NULL;                                                 // No (exported) label
 161         equate = NULL;                                                  // No equate
 162         tk = tok;                                                               // Save first token in line
 163         pcloc = (VALUE)sloc;                                    // Set beginning-of-line PC
 164
 165 loop1:                                                                          // Internal line processing loop
 166
 167         if (*tok == EOL)                                                // Restart loop if end-of-line
 168                 goto loop;
 169
 170         // First token MUST be a symbol
 171         if (*tok != SYMBOL)
 172         {
 173                 error(syntax_error);
 174                 goto loop;
 175         }
 176
 177         j = (int)tok[2];                                                // Skip equates (normal statements)
 178
 179         if (j == '=' || j == DEQUALS || j == SET || j == REG || j == EQUREG || j == CCDEF)
 180         {
 181 //              equate = (char *)tok[1];
 182                 equate = string[tok[1]];
 183                 equtyp = j;
 184                 tok += 3;
 185                 goto normal;
 186         }
 187
 188         // Skip past label (but record it)
 189         if (j == ':' || j == DCOLON)
 190         {
 191 as68label:
 192 //              label = (char *)tok[1];                         // Get label name
 193                 label = string[tok[1]];                         // Get label name
 194                 labtyp = tok[2];                                        // Get label type
 195                 tok += 3;                                                       // Go to next line token
 196
 197                 // Handle multiple labels; if there's another label, go process it,
 198                 // and come back at `as68label' above.
 199                 if (as68_flag)
 200                 {
 201                         as68mode = 0;
 202
 203                         if (*tok == SYMBOL && tok[2] == ':')
 204                         {
 205                                 as68mode = 1;
 206                                 goto do_label;
 207                         }
 208                 }
 209         }
 210
 211         if (*tok == EOL)                                                // EOL is legal here...
 212                 goto normal;
 213
 214         // Next token MUST be a symbol
 215         if (*tok++ != SYMBOL)
 216         {
 217                 error(syntax_error);
 218                 goto loop;
 219         }
 220
 221 // This is the problem here: On 64-bit platforms, this cuts the native pointer
 222 // in half. We need to figure out how to fix this.
 223 //#warning "!!! Bad pointer !!!"
 224 #if 0
 225         opname = p = (char *)*tok++;                    // Store opcode name here
 226 #else
 227         opname = p = string[*tok++];
 228 #endif
 229
 230         // Check to see if the SYMBOL is a keyword (a mnemonic or directive).
 231         // On output, `state' will have one of the values:
 232         //    -3          there was no symbol (EOL)
 233         //    -2..-1      the symbol didn't match any keyword
 234         //    0..499      vanilla directives (dc, ds, etc.)
 235         //    500..999    electric directives (macro, rept, etc.)
 236         //    1000..+     mnemonics (move, lsr, etc.)
 237         for(state=0; state>=0;)
 238         {
 239                 j = mnbase[state] + (int)tolowertab[*p];
 240
 241                 // Reject, character doesn't match
 242                 if (mncheck[j] != state)
 243                 {
 244                         state = -1;                                             // No match
 245                         break;
 246                 }
 247
 248                 // Must accept or reject at EOS
 249                 if (!*++p)
 250                 {
 251                         state = mnaccept[j];                    // (-1 on no terminal match)
 252                         break;
 253                 }
 254
 255                 state = mntab[j];
 256         }
 257
 258         // Check for ".b" ".w" ".l" after directive, macro or mnemonic.
 259         siz = SIZN;
 260
 261         if (*tok == DOTW)
 262                 siz = SIZW, ++tok;
 263         else if (*tok == DOTL)
 264                 siz = SIZL, ++tok;
 265         else if (*tok == DOTB)
 266                 siz = SIZB, ++tok;
 267
 268         // Do special directives (500..999) (These must be handled in "real time")
 269         if (state >= 500 && state < 1000)
 270         {
 271                 switch (state)
 272                 {
 273                 case MN_IF:
 274                         d_if ();
 275                 goto loop;
 276                 case MN_ELSE:
 277                         d_else();
 278                         goto loop;
 279                 case MN_ENDIF:
 280                         d_endif ();
 281                         goto loop;
 282                 case MN_IIF:                                            // .iif --- immediate if
 283                         if (disabled || expr(exprbuf, &eval, &eattr, &esym) != OK)
 284                                 goto loop;
 285
 286                         if (!(eattr & DEFINED))
 287                         {
 288                                 error(undef_error);
 289                                 goto loop;
 290                         }
 291
 292                         if (*tok++ != ',')
 293                         {
 294                                 error(comma_error);
 295                                 goto loop;
 296                         }
 297
 298                         if (eval == 0)
 299                                 goto loop;
 300
 301                         goto loop1;
 302                 case MN_MACRO:                                          // .macro --- macro definition
 303                         if (!disabled)
 304                         {
 305                                 if (label != NULL)
 306                                         warn(lab_ignored);
 307
 308                                 DefineMacro();
 309                         }
 310
 311                         goto loop;
 312                 case MN_EXITM:                                          // .exitm --- exit macro
 313                 case MN_ENDM:                                           // .endm --- same as .exitm
 314                         if (!disabled)
 315                         {
 316                                 if (label != NULL)
 317                                         warn(lab_ignored);
 318
 319                                 exitmac();
 320                         }
 321
 322                         goto loop;
 323                 case MN_REPT:
 324                         if (!disabled)
 325                         {
 326                                 if (label != NULL)
 327                                         warn(lab_ignored);
 328
 329                                 defrept();
 330                         }
 331
 332                         goto loop;
 333                 case MN_ENDR:
 334                         if (!disabled)
 335                                 error("mis-nested .endr");
 336
 337                         goto loop;
 338                 }
 339         }
 340
 341 normal:
 342         if (disabled)                                                   // Conditionally disabled code
 343                 goto loop;
 344
 345         // Do equates
 346         if (equate != NULL)
 347         {
 348                 j = 0;                                                          // Pick global or local sym enviroment
 349
 350                 if (*equate == '.')
 351                         j = curenv;
 352
 353                 sy = lookup(equate, LABEL, j);
 354
 355                 if (sy == NULL)
 356                 {
 357                         sy = NewSymbol(equate, LABEL, j);
 358                         sy->sattr = 0;
 359
 360                         if (equtyp == DEQUALS)
 361                         {
 362                                 // Can't GLOBAL a local symbol
 363                                 if (j)
 364                                 {
 365                                         error(locgl_error);
 366                                         goto loop;
 367                                 }
 368
 369                                 sy->sattr = GLOBAL;
 370                         }
 371                 }
 372                 else if ((sy->sattr & DEFINED) && equtyp != SET)
 373                 {
 374                         if ((equtyp == EQUREG) && (sy->sattre & UNDEF_EQUR))
 375                         {
 376                                 sy->sattre |= ~UNDEF_EQUR;
 377                                 sy->svalue  = 0;
 378                         }
 379                         else if ((equtyp == CCDEF) && (sy->sattre & UNDEF_CC))
 380                         {
 381                                 sy->sattre |= ~UNDEF_CC;
 382                                 sy->svalue = 0;
 383                         }
 384                         else
 385                         {
 386                                 errors("multiple equate to '%s'", sy->sname);
 387                                 goto loop;
 388                         }
 389                 }
 390
 391                 // Put symbol in "order of definition" list
 392                 if (!(sy->sattr & SDECLLIST))
 393                         sym_decl(sy);
 394
 395                 // Parse value to equate symbol to;
 396                 // o  .equr
 397                 // o  .reg
 398                 // o  everything else
 399                 if (equtyp == EQUREG)
 400                 {
 401                         // Check that we are in a RISC section
 402                         if (!rgpu && !rdsp)
 403                         {
 404                                 error(".equr/.regequ must be defined in .gpu/.dsp section");
 405                                 goto loop;
 406                         }
 407
 408                         // Check for register to equate to
 409                         if ((*tok >= KW_R0) && (*tok <= KW_R31))
 410                         {
 411                                 sy->sattre  = EQUATEDREG | RISCSYM;     // Mark as equated register
 412                                 riscreg = (*tok - KW_R0);
 413                                 sy->sattre |= (riscreg << 8);           // Store register number
 414
 415                                 if ((tok[1] == ',') && (tok[2] == CONST))
 416                                 {
 417                                         tok += 3;
 418
 419                                         if (*tok == 0)
 420                                                 registerbank = BANK_0;
 421                                         else if (*tok == 1)
 422                                                 registerbank = BANK_1;
 423                                         else
 424                                                 registerbank = BANK_N;
 425                                 }
 426                                 else
 427                                 {
 428                                         registerbank = BANK_N;
 429                                 }
 430
 431                                 sy->sattre |= regbank;          // Store register bank
 432                                 eattr = ABS | DEFINED | GLOBAL;
 433                                 eval = 0x80000080 + (riscreg) + (registerbank << 8);
 434                                 tok++;
 435                         }
 436                         // Checking for a register symbol
 437                         else if (tok[0] == SYMBOL)
 438                         {
 439 //                              sy2 = lookup((char *)tok[1], LABEL, j);
 440                                 sy2 = lookup(string[tok[1]], LABEL, j);
 441
 442                                 // Make sure symbol is a valid equreg
 443                                 if (!sy2 || !(sy2->sattre & EQUATEDREG))
 444                                 {
 445                                         error("invalid GPU/DSP .equr/.regequ definition");
 446                                         goto loop;
 447                                 }
 448                                 else
 449                                 {
 450                                         eattr = ABS | DEFINED | GLOBAL; // Copy symbols attributes
 451                                         sy->sattre = sy2->sattre;
 452                                         eval = (sy2->svalue & 0xFFFFF0FF);
 453                                         tok += 2;
 454                                 }
 455                         }
 456                         else
 457                         {
 458                                 error("invalid GPU/DSP .equr/.regequ definition");
 459                                 goto loop;
 460                         }
 461                 }
 462                 else if (equtyp == REG)
 463                 {
 464                         if (reglist(&rmask) < 0)
 465                                 goto loop;
 466
 467                         eval = (VALUE)rmask;
 468                         eattr = ABS | DEFINED;
 469                 }
 470                 else if (equtyp == CCDEF)
 471                 {
 472                         sy->sattre |= EQUATEDCC;
 473                         eattr = ABS | DEFINED | GLOBAL;
 474
 475                         if (tok[0] == SYMBOL)
 476                         {
 477 //                              sy2 = lookup((char *)tok[1], LABEL, j);
 478                                 sy2 = lookup(string[tok[1]], LABEL, j);
 479
 480                                 if (!sy2 || !(sy2->sattre & EQUATEDCC))
 481                                 {
 482                                         error("invalid gpu/dsp .ccdef definition");
 483                                         goto loop;
 484                                 }
 485                                 else
 486                                 {
 487                                         eattr = ABS | DEFINED | GLOBAL;
 488                                         sy->sattre = sy2->sattre;
 489                                         eval = sy2->svalue;
 490                                         tok += 2;
 491                                 }
 492                         }
 493                         else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 494                                 goto loop;
 495                 }
 496                 //equ a equr
 497                 else if (*tok == SYMBOL)
 498                 {
 499 //                      sy2 = lookup((char *)tok[1], LABEL, j);
 500                         sy2 = lookup(string[tok[1]], LABEL, j);
 501
 502                         if (sy2 && (sy2->sattre & EQUATEDREG))
 503                         {
 504                                 sy->stype = sy2->stype;
 505                                 sy->sattr = sy2->sattr;
 506                                 sy->sattre = sy2->sattre;
 507                                 sy->svalue = (sy2->svalue & 0xFFFFF0FF);
 508                                 goto loop;
 509                         }
 510                         else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 511                                 goto loop;
 512                 }
 513                 else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 514                         goto loop;
 515
 516                 if (!(eattr & DEFINED))
 517                 {
 518                         error(undef_error);
 519                         goto loop;
 520                 }
 521
 522                 sy->sattr |= eattr | EQUATED;           // Symbol inherits value and attributes
 523                 sy->svalue = eval;
 524
 525                 if (list_flag)                                          // Put value in listing
 526                         listvalue(eval);
 527
 528                 at_eol();                                                       // Must be at EOL now
 529                 goto loop;
 530         }
 531
 532         // Do labels
 533         if (label != NULL)
 534         {
 535 do_label:
 536                 j = 0;
 537
 538                 if (*label == '.')
 539                         j = curenv;
 540
 541                 sy = lookup(label, LABEL, j);
 542
 543                 if (sy == NULL)
 544                 {
 545                         sy = NewSymbol(label, LABEL, j);
 546                         sy->sattr = 0;
 547                         sy->sattre = RISCSYM;
 548                 }
 549                 else if (sy->sattr & DEFINED)
 550                 {
 551                         errors("multiply-defined label '%s'", label);
 552                         goto loop;
 553                 }
 554
 555                 // Put symbol in "order of definition" list
 556                 if (!(sy->sattr & SDECLLIST))
 557                         sym_decl(sy);
 558
 559                 if (orgactive)
 560                 {
 561                         sy->svalue = orgaddr;
 562                         sy->sattr |= ABS | DEFINED | EQUATED;
 563                 }
 564                 else
 565                 {
 566                         sy->svalue = sloc;
 567                         sy->sattr |= DEFINED | cursect;
 568                 }
 569
 570                 lab_sym = sy;
 571
 572                 if (!j)
 573                         ++curenv;
 574
 575                 // Make label global
 576                 if (labtyp == DCOLON)
 577                 {
 578                         if (j)
 579                         {
 580                                 error(locgl_error);
 581                                 goto loop;
 582                         }
 583
 584                         sy->sattr |= GLOBAL;
 585                 }
 586
 587                 // If we're in as68 mode, and there's another label, go back and handle it
 588                 if (as68_flag && as68mode)
 589                         goto as68label;
 590         }
 591
 592         // Punt on EOL
 593         if (state == -3)
 594                 goto loop;
 595
 596         // If we are in GPU or DSP mode and still in need of a mnemonic then search
 597         // for one
 598         if ((rgpu || rdsp) && (state < 0 || state >= 1000))
 599         {
 600                 for(state=0, p=opname; state>=0;)
 601                 {
 602                         j = mrbase[state] + (int)tolowertab[*p];
 603
 604                         // Reject, character doesn't match
 605                         if (mrcheck[j] != state)
 606                         {
 607                                 state = -1;                                     // No match
 608                                 break;
 609                         }
 610
 611                         // Must accept or reject at EOS
 612                         if (!*++p)
 613                         {
 614                                 state = mraccept[j];            // (-1 on no terminal match)
 615                                 break;
 616                         }
 617
 618                         state = mrtab[j];
 619                 }
 620
 621                 // Call RISC code generator if we found a mnemonic
 622                 if (state >= 3000)
 623                 {
 624                         risccg(state);
 625                         goto loop;
 626                 }
 627         }
 628
 629         // Invoke macro or complain about bad mnemonic
 630         if (state < 0)
 631         {
 632                 if ((sy = lookup(opname, MACRO, 0)) != NULL)
 633                         InvokeMacro(sy, siz);
 634                 else
 635                         errors("unknown op '%s'", opname);
 636
 637                 goto loop;
 638         }
 639
 640         // Call directive handlers
 641         if (state < 500)
 642         {
 643                 (*dirtab[state])(siz);
 644                 goto loop;
 645         }
 646
 647         // Do mnemonics
 648         // o  can't deposit instrs in BSS or ABS
 649         // o  do automatic .EVEN for instrs
 650         // o  allocate space for largest possible instr
 651         // o  can't do ".b" operations with an address register
 652         if (scattr & SBSS)
 653         {
 654                 error("cannot initialize non-storage (BSS) section");
 655                 goto loop;
 656         }
 657
 658         if (sloc & 1)                                                   // Automatic .even
 659                 auto_even();
 660
 661         if (challoc - ch_size < 18)                             // Make sure have space in current chunk
 662                 chcheck(0);
 663
 664         m = &machtab[state - 1000];
 665
 666         // Call special-mode handler
 667         if (m->mnattr & CGSPECIAL)
 668         {
 669                 (*m->mnfunc)(m->mninst, siz);
 670                 goto loop;
 671         }
 672
 673         if (amode(1) < 0)                                               // Parse 0, 1 or 2 addr modes
 674                 goto loop;
 675
 676         if (*tok != EOL)
 677                 error(extra_stuff);
 678
 679         amsk0 = amsktab[am0];
 680         amsk1 = amsktab[am1];
 681
 682         // Catch attempts to use ".B" with an address register (yes, this check
 683         // does work at this level)
 684         if (siz == SIZB && (am0 == AREG || am1 == AREG))
 685         {
 686                 error("cannot use '.b' with an address register");
 687                 goto loop;
 688         }
 689
 690         for(;;)
 691         {
 692                 if ((m->mnattr & siz) && (amsk0 & m->mn0) != 0 && (amsk1 & m->mn1) != 0)
 693                 {
 694                         (*m->mnfunc)(m->mninst, siz);
 695                         goto loop;
 696                 }
 697
 698                 m = &machtab[m->mncont];
 699         }
 700 }
 701
 702
 703 //
 704 // .if, Start Conditional Assembly
 705 //
 706 int d_if(void)
 707 {
 708         IFENT * rif;
 709         WORD eattr;
 710         VALUE eval;
 711         SYM * esym;
 712
 713         // Alloc an IFENTRY
 714         if ((rif = f_ifent) == NULL)
 715                 rif = (IFENT *)malloc(sizeof(IFENT));
 716         else
 717                 f_ifent = rif->if_prev;
 718
 719         rif->if_prev = ifent;
 720         ifent = rif;
 721
 722         if (!disabled)
 723         {
 724                 if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 725                         return 0;
 726
 727                 if ((eattr & DEFINED) == 0)
 728                         return error(undef_error);
 729
 730                 disabled = !eval;
 731         }
 732
 733         rif->if_state = (WORD)disabled;
 734         return 0;
 735 }
 736
 737
 738 //
 739 // .else, Do Alternate Case For .if
 740 //
 741 int d_else(void)
 742 {
 743         IFENT * rif = ifent;
 744
 745         if (rif->if_prev == NULL)
 746                 return error("mismatched .else");
 747
 748         if (disabled)
 749                 disabled = rif->if_prev->if_state;
 750         else
 751                 disabled = 1;
 752
 753         rif->if_state = (WORD)disabled;
 754         return 0;
 755 }
 756
 757
 758 //
 759 // .endif, End of conditional assembly block
 760 // This is also called by fpop() to pop levels of IFENTs in case a macro or
 761 // include file exits early with `exitm' or `end'.
 762 //
 763 int d_endif (void)
 764 {
 765         IFENT * rif = ifent;
 766
 767         if (rif->if_prev == NULL)
 768                 return error("mismatched .endif");
 769
 770         ifent = rif->if_prev;
 771         disabled = rif->if_prev->if_state;
 772         rif->if_prev = f_ifent;
 773         f_ifent = rif;
 774         return 0;
 775 }