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 "riscasm.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
  33 IFENT * ifent;                                  // Current ifent
  34 static IFENT ifent0;                    // Root ifent
  35 static IFENT * f_ifent;                 // Freelist of ifents
  36 static int disabled;                    // Assembly conditionally disabled
  37 int just_bss;                                   // 1, ds.b in microprocessor mode
  38 VALUE pcloc;                                    // Value of "PC" at beginning of line
  39 IFENT * ifent;                                  // Current ifent
  40 SYM * lab_sym;                                  // Label on line (or NULL)
  41
  42 char extra_stuff[] = "extra (unexpected) text found after addressing mode";
  43 char * comma_error = "missing comma";
  44 char * syntax_error = "syntax error";
  45 char * locgl_error = "cannot GLOBL local symbol";
  46 char * lab_ignored = "label ignored";
  47
  48 // Table to convert an addressing-mode number to a bitmask.
  49 LONG amsktab[0112] = {
  50         M_DREG, M_DREG, M_DREG, M_DREG,
  51         M_DREG, M_DREG, M_DREG, M_DREG,
  52
  53         M_AREG, M_AREG, M_AREG, M_AREG,
  54         M_AREG, M_AREG, M_AREG, M_AREG,
  55
  56         M_AIND, M_AIND, M_AIND, M_AIND,
  57         M_AIND, M_AIND, M_AIND, M_AIND,
  58
  59         M_APOSTINC, M_APOSTINC, M_APOSTINC, M_APOSTINC,
  60         M_APOSTINC, M_APOSTINC, M_APOSTINC, M_APOSTINC,
  61
  62         M_APREDEC, M_APREDEC, M_APREDEC, M_APREDEC,
  63         M_APREDEC, M_APREDEC, M_APREDEC, M_APREDEC,
  64
  65         M_ADISP, M_ADISP, M_ADISP, M_ADISP,
  66         M_ADISP, M_ADISP, M_ADISP, M_ADISP,
  67
  68         M_AINDEXED, M_AINDEXED, M_AINDEXED, M_AINDEXED,
  69         M_AINDEXED, M_AINDEXED, M_AINDEXED, M_AINDEXED,
  70
  71         M_ABSW,                                                                                 // 070
  72         M_ABSL,                                                                                 // 071
  73         M_PCDISP,                                                                               // 072
  74         M_PCINDEXED,                                                                    // 073
  75         M_IMMED,                                                                                // 074
  76         0L,                                                                                             // 075
  77         0L,                                                                                             // 076
  78         0L,                                                                                             // 077
  79         M_ABASE,                                                                                // 0100
  80         M_MEMPOST,                                                                              // 0101
  81         M_MEMPRE,                                                                               // 0102
  82         M_PCBASE,                                                                               // 0103
  83         M_PCMPOST,                                                                              // 0104
  84         M_PCMPRE,                                                                               // 0105
  85         M_AM_USP,                                                                               // 0106
  86         M_AM_SR,                                                                                // 0107
  87         M_AM_CCR,                                                                               // 0110
  88         M_AM_NONE                                                                               // 0111
  89 };                                                                                                      // 0112 length
  90
  91
  92 //
  93 // Initialize Line Processor
  94 //
  95 void init_procln(void)
  96 {
  97         disabled = 0;
  98         ifent = &ifent0;
  99         f_ifent = ifent0.if_prev = NULL;
 100         ifent0.if_state = 0;
 101 }
 102
 103
 104 //
 105 // Line Processor
 106 //
 107 void Assemble(void)
 108 {
 109         int state;                                      // Keyword machine state (output)
 110         int j;                                          // Random int, must be fast
 111         char * p;                                       // Random char ptr, must be fast
 112         TOKEN * tk;                                     // First token in line
 113         char * label;                           // Symbol (or NULL)
 114         char * equate;                          // Symbol (or NULL)
 115         int labtyp = 0;                         // Label type (':', DCOLON)
 116         int equtyp = 0;                         // Equ type ('=', DEQUALS)
 117         VALUE eval;                                     // Expression value
 118         WORD eattr;                                     // Expression attributes
 119         SYM * esym;                                     // External symbol involved in expr.
 120         WORD siz = 0;                           // Size suffix to mnem/diretve/macro
 121         LONG amsk0, amsk1;                      // Address-type masks for ea0, ea1
 122         MNTAB * m;                                      // Code generation table pointer
 123         SYM * sy, * sy2;                        // Symbol (temp usage)
 124         char * opname = NULL;           // Name of dirctve/mnemonic/macro
 125         int listflag;                           // 0: Don't call listeol()
 126         int as68mode = 0;                       // 1: Handle multiple labels
 127         WORD rmask;                                     // Register list, for REG
 128         int registerbank;                       // RISC register bank
 129         int riscreg;                            // RISC register
 130
 131         listflag = 0;                           // Initialise listing flag
 132
 133 loop:                                                   // Line processing loop label
 134
 135         // Get another line of tokens
 136         if (tokln() == TKEOF)
 137         {
 138 if (verb_flag) printf("Assemble: Found TKEOF flag...\n");
 139                 if (list_flag && listflag)                      // Flush last line of source
 140                         listeol();
 141
 142                 if (ifent->if_prev != NULL)                     // Check conditional token
 143                         error("hit EOF without finding matching .endif");
 144
 145                 return;
 146         }
 147
 148         DEBUG DumpTokenBuffer();
 149
 150         if (list_flag)
 151         {
 152                 if (listflag && listing > 0)
 153                         listeol();                                              // Tell listing generator about EOL
 154
 155                 lstout((char)(disabled ? '-' : lntag)); // Prepare new line for listing
 156                 listflag = 1;                                           // OK to call `listeol' now
 157                 just_bss = 0;                                           // Reset just_bss mode
 158         }
 159
 160         state = -3;                                                             // No keyword (just EOL)
 161         label = NULL;                                                   // No label
 162         lab_sym = NULL;                                                 // No (exported) label
 163         equate = NULL;                                                  // No equate
 164         tk = tok;                                                               // Save first token in line
 165         pcloc = (VALUE)sloc;                                    // Set beginning-of-line PC
 166
 167 loop1:                                                                          // Internal line processing loop
 168
 169         if (*tok == EOL)                                                // Restart loop if end-of-line
 170                 goto loop;
 171
 172         // First token MUST be a symbol
 173         if (*tok != SYMBOL)
 174         {
 175                 error(syntax_error);
 176                 goto loop;
 177         }
 178
 179         j = (int)tok[2];                                                // Skip equates (normal statements)
 180
 181         if (j == '=' || j == DEQUALS || j == SET || j == REG || j == EQUREG || j == CCDEF)
 182         {
 183 //              equate = (char *)tok[1];
 184                 equate = string[tok[1]];
 185                 equtyp = j;
 186                 tok += 3;
 187                 goto normal;
 188         }
 189
 190         // Skip past label (but record it)
 191         if (j == ':' || j == DCOLON)
 192         {
 193 as68label:
 194 //              label = (char *)tok[1];                         // Get label name
 195                 label = string[tok[1]];                         // Get label name
 196                 labtyp = tok[2];                                        // Get label type
 197                 tok += 3;                                                       // Go to next line token
 198
 199                 // Handle multiple labels; if there's another label, go process it,
 200                 // and come back at `as68label' above.
 201                 if (as68_flag)
 202                 {
 203                         as68mode = 0;
 204
 205                         if (*tok == SYMBOL && tok[2] == ':')
 206                         {
 207                                 as68mode = 1;
 208                                 goto do_label;
 209                         }
 210                 }
 211         }
 212
 213         if (*tok == EOL)                                                // EOL is legal here...
 214                 goto normal;
 215
 216         // Next token MUST be a symbol
 217         if (*tok++ != SYMBOL)
 218         {
 219                 error(syntax_error);
 220                 goto loop;
 221         }
 222
 223 // This is the problem here: On 64-bit platforms, this cuts the native pointer
 224 // in half. We need to figure out how to fix this.
 225 //#warning "!!! Bad pointer !!!"
 226 #if 0
 227         opname = p = (char *)*tok++;                    // Store opcode name here
 228 #else
 229         opname = p = string[*tok++];
 230 #endif
 231
 232         // Check to see if the SYMBOL is a keyword (a mnemonic or directive).
 233         // On output, `state' will have one of the values:
 234         //    -3          there was no symbol (EOL)
 235         //    -2..-1      the symbol didn't match any keyword
 236         //    0..499      vanilla directives (dc, ds, etc.)
 237         //    500..999    electric directives (macro, rept, etc.)
 238         //    1000..+     mnemonics (move, lsr, etc.)
 239         for(state=0; state>=0;)
 240         {
 241                 j = mnbase[state] + (int)tolowertab[*p];
 242
 243                 // Reject, character doesn't match
 244                 if (mncheck[j] != state)
 245                 {
 246                         state = -1;                                             // No match
 247                         break;
 248                 }
 249
 250                 // Must accept or reject at EOS
 251                 if (!*++p)
 252                 {
 253                         state = mnaccept[j];                    // (-1 on no terminal match)
 254                         break;
 255                 }
 256
 257                 state = mntab[j];
 258         }
 259
 260         // Check for ".b" ".w" ".l" after directive, macro or mnemonic.
 261         siz = SIZN;
 262
 263         if (*tok == DOTW)
 264                 siz = SIZW, ++tok;
 265         else if (*tok == DOTL)
 266                 siz = SIZL, ++tok;
 267         else if (*tok == DOTB)
 268                 siz = SIZB, ++tok;
 269
 270         // Do special directives (500..999) (These must be handled in "real time")
 271         if (state >= 500 && state < 1000)
 272         {
 273                 switch (state)
 274                 {
 275                 case MN_IF:
 276                         d_if ();
 277                 goto loop;
 278                 case MN_ELSE:
 279                         d_else();
 280                         goto loop;
 281                 case MN_ENDIF:
 282                         d_endif ();
 283                         goto loop;
 284                 case MN_IIF:                                            // .iif --- immediate if
 285                         if (disabled || expr(exprbuf, &eval, &eattr, &esym) != OK)
 286                                 goto loop;
 287
 288                         if (!(eattr & DEFINED))
 289                         {
 290                                 error(undef_error);
 291                                 goto loop;
 292                         }
 293
 294                         if (*tok++ != ',')
 295                         {
 296                                 error(comma_error);
 297                                 goto loop;
 298                         }
 299
 300                         if (eval == 0)
 301                                 goto loop;
 302
 303                         goto loop1;
 304                 case MN_MACRO:                                          // .macro --- macro definition
 305                         if (!disabled)
 306                         {
 307                                 if (label != NULL)
 308                                         warn(lab_ignored);
 309
 310                                 DefineMacro();
 311                         }
 312
 313                         goto loop;
 314                 case MN_EXITM:                                          // .exitm --- exit macro
 315                 case MN_ENDM:                                           // .endm --- same as .exitm
 316                         if (!disabled)
 317                         {
 318                                 if (label != NULL)
 319                                         warn(lab_ignored);
 320
 321                                 ExitMacro();
 322                         }
 323
 324                         goto loop;
 325                 case MN_REPT:
 326                         if (!disabled)
 327                         {
 328                                 if (label != NULL)
 329                                         warn(lab_ignored);
 330
 331                                 defrept();
 332                         }
 333
 334                         goto loop;
 335                 case MN_ENDR:
 336                         if (!disabled)
 337                                 error("mis-nested .endr");
 338
 339                         goto loop;
 340                 }
 341         }
 342
 343 normal:
 344         if (disabled)                                                   // Conditionally disabled code
 345                 goto loop;
 346
 347         // Do equates
 348         if (equate != NULL)
 349         {
 350                 j = 0;                                                          // Pick global or local sym enviroment
 351
 352                 if (*equate == '.')
 353                         j = curenv;
 354
 355                 sy = lookup(equate, LABEL, j);
 356
 357                 if (sy == NULL)
 358                 {
 359                         sy = NewSymbol(equate, LABEL, j);
 360                         sy->sattr = 0;
 361
 362                         if (equtyp == DEQUALS)
 363                         {
 364                                 // Can't GLOBAL a local symbol
 365                                 if (j)
 366                                 {
 367                                         error(locgl_error);
 368                                         goto loop;
 369                                 }
 370
 371                                 sy->sattr = GLOBAL;
 372                         }
 373                 }
 374                 else if ((sy->sattr & DEFINED) && equtyp != SET)
 375                 {
 376                         if ((equtyp == EQUREG) && (sy->sattre & UNDEF_EQUR))
 377                         {
 378 //REALLY?                               sy->sattre |= ~UNDEF_EQUR;
 379                                 sy->sattre &= ~UNDEF_EQUR;
 380                                 sy->svalue  = 0;
 381                         }
 382                         else if ((equtyp == CCDEF) && (sy->sattre & UNDEF_CC))
 383                         {
 384 //REALLY?                               sy->sattre |= ~UNDEF_CC;
 385                                 sy->sattre &= ~UNDEF_CC;
 386                                 sy->svalue = 0;
 387                         }
 388                         else
 389                         {
 390                                 errors("multiple equate to '%s'", sy->sname);
 391                                 goto loop;
 392                         }
 393                 }
 394
 395                 // Put symbol in "order of definition" list
 396                 if (!(sy->sattr & SDECLLIST))
 397                         sym_decl(sy);
 398
 399                 // Parse value to equate symbol to;
 400                 // o  .equr
 401                 // o  .reg
 402                 // o  everything else
 403                 if (equtyp == EQUREG)
 404                 {
 405                         // Check that we are in a RISC section
 406                         if (!rgpu && !rdsp)
 407                         {
 408                                 error(".equr/.regequ must be defined in .gpu/.dsp section");
 409                                 goto loop;
 410                         }
 411
 412                         // Check for register to equate to
 413                         if ((*tok >= KW_R0) && (*tok <= KW_R31))
 414                         {
 415                                 sy->sattre  = EQUATEDREG | RISCSYM;     // Mark as equated register
 416                                 riscreg = (*tok - KW_R0);
 417                                 sy->sattre |= (riscreg << 8);           // Store register number
 418
 419                                 if ((tok[1] == ',') && (tok[2] == CONST))
 420                                 {
 421                                         tok += 3;
 422
 423                                         if (*tok == 0)
 424                                                 registerbank = BANK_0;
 425                                         else if (*tok == 1)
 426                                                 registerbank = BANK_1;
 427                                         else
 428                                                 registerbank = BANK_N;
 429                                 }
 430                                 else
 431                                 {
 432                                         registerbank = BANK_N;
 433                                 }
 434
 435                                 sy->sattre |= regbank;          // Store register bank
 436                                 eattr = ABS | DEFINED | GLOBAL;
 437                                 eval = 0x80000080 + (riscreg) + (registerbank << 8);
 438                                 tok++;
 439                         }
 440                         // Checking for a register symbol
 441                         else if (tok[0] == SYMBOL)
 442                         {
 443 //                              sy2 = lookup((char *)tok[1], LABEL, j);
 444                                 sy2 = lookup(string[tok[1]], LABEL, j);
 445
 446                                 // Make sure symbol is a valid equreg
 447                                 if (!sy2 || !(sy2->sattre & EQUATEDREG))
 448                                 {
 449                                         error("invalid GPU/DSP .equr/.regequ definition");
 450                                         goto loop;
 451                                 }
 452                                 else
 453                                 {
 454                                         eattr = ABS | DEFINED | GLOBAL; // Copy symbols attributes
 455                                         sy->sattre = sy2->sattre;
 456                                         eval = (sy2->svalue & 0xFFFFF0FF);
 457                                         tok += 2;
 458                                 }
 459                         }
 460                         else
 461                         {
 462                                 error("invalid GPU/DSP .equr/.regequ definition");
 463                                 goto loop;
 464                         }
 465                 }
 466                 else if (equtyp == REG)
 467                 {
 468                         if (reglist(&rmask) < 0)
 469                                 goto loop;
 470
 471                         eval = (VALUE)rmask;
 472                         eattr = ABS | DEFINED;
 473                 }
 474                 else if (equtyp == CCDEF)
 475                 {
 476                         sy->sattre |= EQUATEDCC;
 477                         eattr = ABS | DEFINED | GLOBAL;
 478
 479                         if (tok[0] == SYMBOL)
 480                         {
 481 //                              sy2 = lookup((char *)tok[1], LABEL, j);
 482                                 sy2 = lookup(string[tok[1]], LABEL, j);
 483
 484                                 if (!sy2 || !(sy2->sattre & EQUATEDCC))
 485                                 {
 486                                         error("invalid gpu/dsp .ccdef definition");
 487                                         goto loop;
 488                                 }
 489                                 else
 490                                 {
 491                                         eattr = ABS | DEFINED | GLOBAL;
 492                                         sy->sattre = sy2->sattre;
 493                                         eval = sy2->svalue;
 494                                         tok += 2;
 495                                 }
 496                         }
 497                         else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 498                                 goto loop;
 499                 }
 500                 //equ a equr
 501                 else if (*tok == SYMBOL)
 502                 {
 503 //                      sy2 = lookup((char *)tok[1], LABEL, j);
 504                         sy2 = lookup(string[tok[1]], LABEL, j);
 505
 506                         if (sy2 && (sy2->sattre & EQUATEDREG))
 507                         {
 508                                 sy->stype = sy2->stype;
 509                                 sy->sattr = sy2->sattr;
 510                                 sy->sattre = sy2->sattre;
 511                                 sy->svalue = (sy2->svalue & 0xFFFFF0FF);
 512                                 goto loop;
 513                         }
 514                         else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 515                                 goto loop;
 516                 }
 517                 else if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 518                         goto loop;
 519
 520                 if (!(eattr & DEFINED))
 521                 {
 522                         error(undef_error);
 523                         goto loop;
 524                 }
 525
 526                 sy->sattr |= eattr | EQUATED;           // Symbol inherits value and attributes
 527                 sy->svalue = eval;
 528
 529                 if (list_flag)                                          // Put value in listing
 530                         listvalue(eval);
 531
 532                 at_eol();                                                       // Must be at EOL now
 533                 goto loop;
 534         }
 535
 536         // Do labels
 537         if (label != NULL)
 538         {
 539 do_label:
 540                 // Check for dot in front of label; means this is a local label if present
 541 #if 0
 542                 j = 0;
 543
 544                 if (*label == '.')
 545                         j = curenv;
 546 #else
 547                 j = (*label == '.' ? curenv : 0);
 548 #endif
 549
 550                 sy = lookup(label, LABEL, j);
 551
 552                 if (sy == NULL)
 553                 {
 554                         sy = NewSymbol(label, LABEL, j);
 555                         sy->sattr = 0;
 556                         sy->sattre = RISCSYM;
 557                 }
 558                 else if (sy->sattr & DEFINED)
 559                 {
 560                         errors("multiply-defined label '%s'", label);
 561                         goto loop;
 562                 }
 563
 564                 // Put symbol in "order of definition" list
 565                 if (!(sy->sattr & SDECLLIST))
 566                         sym_decl(sy);
 567
 568                 if (orgactive)
 569                 {
 570                         sy->svalue = orgaddr;
 571                         sy->sattr |= ABS | DEFINED | EQUATED;
 572                 }
 573                 else
 574                 {
 575                         sy->svalue = sloc;
 576                         sy->sattr |= DEFINED | cursect;
 577                 }
 578
 579                 lab_sym = sy;
 580
 581                 if (!j)
 582                         curenv++;
 583
 584                 // Make label global
 585                 if (labtyp == DCOLON)
 586                 {
 587                         if (j)
 588                         {
 589                                 error(locgl_error);
 590                                 goto loop;
 591                         }
 592
 593                         sy->sattr |= GLOBAL;
 594                 }
 595
 596                 // If we're in as68 mode, and there's another label, go back and handle it
 597                 if (as68_flag && as68mode)
 598                         goto as68label;
 599         }
 600
 601         // Punt on EOL
 602         if (state == -3)
 603                 goto loop;
 604
 605         // If we are in GPU or DSP mode and still in need of a mnemonic then search
 606         // for one
 607         if ((rgpu || rdsp) && (state < 0 || state >= 1000))
 608         {
 609                 for(state=0, p=opname; state>=0;)
 610                 {
 611                         j = mrbase[state] + (int)tolowertab[*p];
 612
 613                         // Reject, character doesn't match
 614                         if (mrcheck[j] != state)
 615                         {
 616                                 state = -1;                                     // No match
 617                                 break;
 618                         }
 619
 620                         // Must accept or reject at EOS
 621                         if (!*++p)
 622                         {
 623                                 state = mraccept[j];            // (-1 on no terminal match)
 624                                 break;
 625                         }
 626
 627                         state = mrtab[j];
 628                 }
 629
 630                 // Call RISC code generator if we found a mnemonic
 631                 if (state >= 3000)
 632                 {
 633                         GenerateRISCCode(state);
 634                         goto loop;
 635                 }
 636         }
 637
 638         // Invoke macro or complain about bad mnemonic
 639         if (state < 0)
 640         {
 641                 if ((sy = lookup(opname, MACRO, 0)) != NULL)
 642                         InvokeMacro(sy, siz);
 643                 else
 644                         errors("unknown op '%s'", opname);
 645
 646                 goto loop;
 647         }
 648
 649         // Call directive handlers
 650         if (state < 500)
 651         {
 652                 (*dirtab[state])(siz);
 653                 goto loop;
 654         }
 655
 656         // Do mnemonics
 657         // o  can't deposit instrs in BSS or ABS
 658         // o  do automatic .EVEN for instrs
 659         // o  allocate space for largest possible instr
 660         // o  can't do ".b" operations with an address register
 661         if (scattr & SBSS)
 662         {
 663                 error("cannot initialize non-storage (BSS) section");
 664                 goto loop;
 665         }
 666
 667         if (sloc & 1)                                                   // Automatic .even
 668                 auto_even();
 669
 670         if (challoc - ch_size < 18)                             // Make sure have space in current chunk
 671                 chcheck(0);
 672
 673         m = &machtab[state - 1000];
 674
 675         // Call special-mode handler
 676         if (m->mnattr & CGSPECIAL)
 677         {
 678                 (*m->mnfunc)(m->mninst, siz);
 679                 goto loop;
 680         }
 681
 682         if (amode(1) < 0)                                               // Parse 0, 1 or 2 addr modes
 683                 goto loop;
 684
 685         if (*tok != EOL)
 686                 error(extra_stuff);
 687
 688         amsk0 = amsktab[am0];
 689         amsk1 = amsktab[am1];
 690
 691         // Catch attempts to use ".B" with an address register (yes, this check
 692         // does work at this level)
 693         if (siz == SIZB && (am0 == AREG || am1 == AREG))
 694         {
 695                 error("cannot use '.b' with an address register");
 696                 goto loop;
 697         }
 698
 699         for(;;)
 700         {
 701                 if ((m->mnattr & siz) && (amsk0 & m->mn0) != 0 && (amsk1 & m->mn1) != 0)
 702                 {
 703                         (*m->mnfunc)(m->mninst, siz);
 704                         goto loop;
 705                 }
 706
 707                 m = &machtab[m->mncont];
 708         }
 709 }
 710
 711
 712 //
 713 // .if, Start Conditional Assembly
 714 //
 715 int d_if(void)
 716 {
 717         IFENT * rif;
 718         WORD eattr;
 719         VALUE eval;
 720         SYM * esym;
 721
 722         // Alloc an IFENTRY
 723         if ((rif = f_ifent) == NULL)
 724                 rif = (IFENT *)malloc(sizeof(IFENT));
 725         else
 726                 f_ifent = rif->if_prev;
 727
 728         rif->if_prev = ifent;
 729         ifent = rif;
 730
 731         if (!disabled)
 732         {
 733                 if (expr(exprbuf, &eval, &eattr, &esym) != OK)
 734                         return 0;
 735
 736                 if ((eattr & DEFINED) == 0)
 737                         return error(undef_error);
 738
 739                 disabled = !eval;
 740         }
 741
 742         rif->if_state = (WORD)disabled;
 743         return 0;
 744 }
 745
 746
 747 //
 748 // .else, Do Alternate Case For .if
 749 //
 750 int d_else(void)
 751 {
 752         IFENT * rif = ifent;
 753
 754         if (rif->if_prev == NULL)
 755                 return error("mismatched .else");
 756
 757         if (disabled)
 758                 disabled = rif->if_prev->if_state;
 759         else
 760                 disabled = 1;
 761
 762         rif->if_state = (WORD)disabled;
 763         return 0;
 764 }
 765
 766
 767 //
 768 // .endif, End of conditional assembly block
 769 // This is also called by fpop() to pop levels of IFENTs in case a macro or
 770 // include file exits early with `exitm' or `end'.
 771 //
 772 int d_endif (void)
 773 {
 774         IFENT * rif = ifent;
 775
 776         if (rif->if_prev == NULL)
 777                 return error("mismatched .endif");
 778
 779         ifent = rif->if_prev;
 780         disabled = rif->if_prev->if_state;
 781         rif->if_prev = f_ifent;
 782         f_ifent = rif;
 783         return 0;
 784 }