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Annotation of 42BSD/ucb/dbx/events.c, revision 1.1

1.1     ! root        1: /* Copyright (c) 1982 Regents of the University of California */
        !             2: 
        !             3: static char sccsid[] = "@(#)events.c 1.3 4/8/83";
        !             4: 
        !             5: /*
        !             6:  * Event/breakpoint managment.
        !             7:  */
        !             8: 
        !             9: #include "defs.h"
        !            10: #include "events.h"
        !            11: #include "main.h"
        !            12: #include "symbols.h"
        !            13: #include "tree.h"
        !            14: #include "eval.h"
        !            15: #include "source.h"
        !            16: #include "mappings.h"
        !            17: #include "process.h"
        !            18: #include "machine.h"
        !            19: #include "lists.h"
        !            20: 
        !            21: #ifndef public
        !            22: typedef struct Event *Event;
        !            23: typedef struct Breakpoint *Breakpoint;
        !            24: 
        !            25: Boolean inst_tracing;
        !            26: Boolean single_stepping;
        !            27: Boolean isstopped;
        !            28: 
        !            29: #include "symbols.h"
        !            30: 
        !            31: Symbol linesym;
        !            32: Symbol procsym;
        !            33: Symbol pcsym;
        !            34: Symbol retaddrsym;
        !            35: 
        !            36: #define addevent(cond, cmdlist) event_alloc(false, cond, cmdlist)
        !            37: #define event_once(cond, cmdlist) event_alloc(true, cond, cmdlist)
        !            38: 
        !            39: #endif
        !            40: 
        !            41: struct Event {
        !            42:     unsigned int id;
        !            43:     Boolean temporary;
        !            44:     Node condition;
        !            45:     Cmdlist actions;
        !            46: };
        !            47: 
        !            48: struct Breakpoint {
        !            49:     Event event;
        !            50:     Address bpaddr;    
        !            51:     Lineno bpline;
        !            52:     Cmdlist actions;
        !            53: };
        !            54: 
        !            55: typedef List Eventlist;
        !            56: typedef List Bplist;
        !            57: 
        !            58: #define eventlist_append(event, el) list_append(list_item(event), nil, el)
        !            59: #define bplist_append(bp, bl) list_append(list_item(bp), nil, bl)
        !            60: 
        !            61: private Eventlist eventlist;           /* list of active events */
        !            62: private Bplist bplist;                 /* list of active breakpoints */
        !            63: private Integer eventid;               /* id number of next allocated event */
        !            64: private Integer trid;                  /* id number of next allocated trace */
        !            65: 
        !            66: typedef struct Trcmd {
        !            67:     Integer trid;
        !            68:     Event event;
        !            69:     Cmdlist cmdlist;
        !            70: } *Trcmd;
        !            71: 
        !            72: private List eachline;         /* commands to execute after each line */
        !            73: private List eachinst;         /* commands to execute after each instruction */
        !            74: 
        !            75: private Breakpoint bp_alloc();
        !            76: 
        !            77: /*
        !            78:  * Initialize breakpoint information.
        !            79:  */
        !            80: 
        !            81: private Symbol builtinsym(str, class, type)
        !            82: String str;
        !            83: Symclass class;
        !            84: Symbol type;
        !            85: {
        !            86:     Symbol s;
        !            87: 
        !            88:     s = insert(identname(str, true));
        !            89:     s->language = findlanguage(".s");
        !            90:     s->class = class;
        !            91:     s->type = type;
        !            92:     return s;
        !            93: }
        !            94: 
        !            95: public bpinit()
        !            96: {
        !            97:     linesym = builtinsym("$line", VAR, t_int);
        !            98:     procsym = builtinsym("$proc", PROC, nil);
        !            99:     pcsym = lookup(identname("$pc", true));
        !           100:     if (pcsym == nil) {
        !           101:        panic("can't find $pc");
        !           102:     }
        !           103:     retaddrsym = builtinsym("$retaddr", VAR, t_int);
        !           104:     eventlist = list_alloc();
        !           105:     bplist = list_alloc();
        !           106:     eachline = list_alloc();
        !           107:     eachinst = list_alloc();
        !           108: }
        !           109: 
        !           110: /*
        !           111:  * Trap an event and do the associated commands when it occurs.
        !           112:  */
        !           113: 
        !           114: public Event event_alloc(istmp, econd, cmdlist)
        !           115: Boolean istmp;
        !           116: Node econd;
        !           117: Cmdlist cmdlist;
        !           118: {
        !           119:     register Event e;
        !           120: 
        !           121:     e = new(Event);
        !           122:     ++eventid;
        !           123:     e->id = eventid;
        !           124:     e->temporary = istmp;
        !           125:     e->condition = econd;
        !           126:     e->actions = cmdlist;
        !           127:     eventlist_append(e, eventlist);
        !           128:     translate(e);
        !           129:     return e;
        !           130: }
        !           131: 
        !           132: /*
        !           133:  * Delete the event with the given id.
        !           134:  */
        !           135: 
        !           136: public delevent(id)
        !           137: unsigned int id;
        !           138: {
        !           139:     Event e;
        !           140:     Breakpoint bp;
        !           141:     Trcmd t;
        !           142: 
        !           143:     foreach (Event, e, eventlist)
        !           144:        if (e->id == id) {
        !           145:            list_delete(list_curitem(eventlist), eventlist);
        !           146:            foreach (Breakpoint, bp, bplist)
        !           147:                if (bp->event == e) {
        !           148:                    list_delete(list_curitem(bplist), bplist);
        !           149:                }
        !           150:            endfor
        !           151:            break;
        !           152:        }
        !           153:     endfor
        !           154:     foreach (Trcmd, t, eachline)
        !           155:        if (t->event->id == id) {
        !           156:            printrmtr(t);
        !           157:            list_delete(list_curitem(eachline), eachline);
        !           158:        }
        !           159:     endfor
        !           160:     foreach (Trcmd, t, eachinst)
        !           161:        if (t->event->id == id) {
        !           162:            printrmtr(t);
        !           163:            list_delete(list_curitem(eachinst), eachinst);
        !           164:        }
        !           165:     endfor
        !           166:     if (list_size(eachinst) == 0) {
        !           167:        inst_tracing = false;
        !           168:        if (list_size(eachline) == 0) {
        !           169:            single_stepping = false;
        !           170:        }
        !           171:     }
        !           172: }
        !           173: 
        !           174: /*
        !           175:  * Translate an event into the appropriate breakpoints and actions.
        !           176:  * While we're at it, turn on the breakpoints if the condition is true.
        !           177:  */
        !           178: 
        !           179: private translate(e)
        !           180: Event e;
        !           181: {
        !           182:     Breakpoint bp;
        !           183:     Symbol s;
        !           184:     Node place;
        !           185:     Lineno line;
        !           186:     Address addr;
        !           187: 
        !           188:     checkref(e->condition);
        !           189:     switch (e->condition->op) {
        !           190:        case O_EQ:
        !           191:            if (e->condition->value.arg[0]->op == O_SYM) {
        !           192:                s = e->condition->value.arg[0]->value.sym;
        !           193:                place = e->condition->value.arg[1];
        !           194:                if (s == linesym) {
        !           195:                    if (place->op == O_QLINE) {
        !           196:                        line = place->value.arg[1]->value.lcon;
        !           197:                        addr = objaddr(line,
        !           198:                            place->value.arg[0]->value.scon);
        !           199:                    } else {
        !           200:                        eval(place);
        !           201:                        line = pop(long);
        !           202:                        addr = objaddr(line, cursource);
        !           203:                    }
        !           204:                    if (addr == NOADDR) {
        !           205:                        delevent(e->id);
        !           206:                        beginerrmsg();
        !           207:                        fprintf(stderr, "no executable code at line ");
        !           208:                        prtree(stderr, place);
        !           209:                        enderrmsg();
        !           210:                    }
        !           211:                    bp = bp_alloc(e, addr, line, e->actions);
        !           212:                } else if (s == procsym) {
        !           213:                    eval(place);
        !           214:                    s = pop(Symbol);
        !           215:                    bp = bp_alloc(e, codeloc(s), 0, e->actions);
        !           216:                    if (isactive(s) and pc != codeloc(program)) {
        !           217:                        evalcmdlist(e->actions);
        !           218:                    }
        !           219:                } else if (s == pcsym) {
        !           220:                    eval(place);
        !           221:                    bp = bp_alloc(e, pop(Address), 0, e->actions);
        !           222:                } else {
        !           223:                    condbp(e);
        !           224:                }
        !           225:            } else {
        !           226:                condbp(e);
        !           227:            }
        !           228:            break;
        !           229: 
        !           230:        /*
        !           231:         * These should be handled specially.
        !           232:         * But for now I'm ignoring the problem.
        !           233:         */
        !           234:        case O_AND:
        !           235:        case O_OR:
        !           236:        default:
        !           237:            condbp(e);
        !           238:            break;
        !           239:     }
        !           240: }
        !           241: 
        !           242: /*
        !           243:  * Create a breakpoint for a condition that cannot be pinpointed
        !           244:  * to happening at a particular address, but one for which we
        !           245:  * must single step and check the condition after each statement.
        !           246:  */
        !           247: 
        !           248: private condbp(e)
        !           249: Event e;
        !           250: {
        !           251:     Symbol p;
        !           252:     Breakpoint bp;
        !           253:     Cmdlist actions;
        !           254: 
        !           255:     p = tcontainer(e->condition);
        !           256:     if (p == nil) {
        !           257:        p = program;
        !           258:     }
        !           259:     actions = buildcmdlist(build(O_IF, e->condition, e->actions));
        !           260:     actions = buildcmdlist(build(O_TRACEON, false, actions));
        !           261:     bp = bp_alloc(e, codeloc(p), 0, actions);
        !           262: }
        !           263: 
        !           264: /*
        !           265:  * Determine the deepest nested subprogram that still contains
        !           266:  * all elements in the given expression.
        !           267:  */
        !           268: 
        !           269: public Symbol tcontainer(exp)
        !           270: Node exp;
        !           271: {
        !           272:     Integer i;
        !           273:     Symbol s, t, u, v;
        !           274: 
        !           275:     checkref(exp);
        !           276:     s = nil;
        !           277:     if (exp->op == O_SYM) {
        !           278:        s = container(exp->value.sym);
        !           279:     } else if (not isleaf(exp->op)) {
        !           280:        for (i = 0; i < nargs(exp->op); i++) {
        !           281:            t = tcontainer(exp->value.arg[i]);
        !           282:            if (t != nil) {
        !           283:                if (s == nil) {
        !           284:                    s = t;
        !           285:                } else {
        !           286:                    u = s;
        !           287:                    v = t;
        !           288:                    while (u != v and u != nil) {
        !           289:                        u = container(u);
        !           290:                        v = container(v);
        !           291:                    }
        !           292:                    if (u == nil) {
        !           293:                        panic("bad ancestry for \"%s\"", symname(s));
        !           294:                    } else {
        !           295:                        s = u;
        !           296:                    }
        !           297:                }
        !           298:            }
        !           299:        }
        !           300:     }
        !           301:     return s;
        !           302: }
        !           303: 
        !           304: /*
        !           305:  * Determine if the given function can be executed at full speed.
        !           306:  * This can only be done if there are no breakpoints within the function.
        !           307:  */
        !           308: 
        !           309: public Boolean canskip(f)
        !           310: Symbol f;
        !           311: {
        !           312:     Breakpoint p;
        !           313:     Boolean ok;
        !           314: 
        !           315:     ok = true;
        !           316:     foreach (Breakpoint, p, bplist)
        !           317:        if (whatblock(p->bpaddr) == f) {
        !           318:            ok = false;
        !           319:            break;
        !           320:        }
        !           321:     endfor
        !           322:     return ok;
        !           323: }
        !           324: 
        !           325: /*
        !           326:  * Print out what's currently being traced by looking at
        !           327:  * the currently active events.
        !           328:  *
        !           329:  * Some convolution here to translate internal representation
        !           330:  * of events back into something more palatable.
        !           331:  */
        !           332: 
        !           333: public status()
        !           334: {
        !           335:     Event e;
        !           336: 
        !           337:     foreach (Event, e, eventlist)
        !           338:        if (not e->temporary) {
        !           339:            printevent(e);
        !           340:        }
        !           341:     endfor
        !           342: }
        !           343: 
        !           344: public printevent(e)
        !           345: Event e;
        !           346: {
        !           347:     Command cmd;
        !           348: 
        !           349:     if (not isredirected()) {
        !           350:        printf("(%d) ", e->id);
        !           351:     }
        !           352:     cmd = list_element(Command, list_head(e->actions));
        !           353:     if (cmd->op == O_PRINTCALL) {
        !           354:        printf("trace ");
        !           355:        printname(stdout, cmd->value.sym);
        !           356:     } else {
        !           357:        if (list_size(e->actions) > 1) {
        !           358:            printf("{ ");
        !           359:        }
        !           360:        foreach (Command, cmd, e->actions)
        !           361:            printcmd(stdout, cmd);
        !           362:            if (not list_islast()) {
        !           363:                printf("; ");
        !           364:            }
        !           365:        endfor
        !           366:        if (list_size(e->actions) > 1) {
        !           367:            printf(" }");
        !           368:        }
        !           369:        printcond(e->condition);
        !           370:     }
        !           371:     printf("\n");
        !           372: }
        !           373: 
        !           374: /*
        !           375:  * Print out a condition.
        !           376:  */
        !           377: 
        !           378: private printcond(cond)
        !           379: Node cond;
        !           380: {
        !           381:     Symbol s;
        !           382:     Node place;
        !           383: 
        !           384:     if (cond->op == O_EQ and cond->value.arg[0]->op == O_SYM) {
        !           385:        s = cond->value.arg[0]->value.sym;
        !           386:        place = cond->value.arg[1];
        !           387:        if (s == procsym) {
        !           388:            if (place->value.sym != program) {
        !           389:                printf(" in ");
        !           390:                printname(stdout, place->value.sym);
        !           391:            }
        !           392:        } else if (s == linesym) {
        !           393:            printf(" at ");
        !           394:            prtree(stdout, place);
        !           395:        } else if (s == pcsym or s == retaddrsym) {
        !           396:            printf("i at ");
        !           397:            prtree(stdout, place);
        !           398:        } else {
        !           399:            printf(" when ");
        !           400:            prtree(stdout, cond);
        !           401:        }
        !           402:     } else {
        !           403:        printf(" when ");
        !           404:        prtree(stdout, cond);
        !           405:     }
        !           406: }
        !           407: 
        !           408: /*
        !           409:  * Add a breakpoint to the list and return it.
        !           410:  */
        !           411: 
        !           412: private Breakpoint bp_alloc(e, addr, line, actions)
        !           413: Event e;
        !           414: Address addr;
        !           415: Lineno line;
        !           416: Cmdlist actions;
        !           417: {
        !           418:     register Breakpoint p;
        !           419: 
        !           420:     p = new(Breakpoint);
        !           421:     p->event = e;
        !           422:     p->bpaddr = addr;
        !           423:     p->bpline = line;
        !           424:     p->actions = actions;
        !           425:     if (tracebpts) {
        !           426:        printf("new bp at 0x%x\n", addr);
        !           427:        fflush(stdout);
        !           428:     }
        !           429:     bplist_append(p, bplist);
        !           430:     return p;
        !           431: }
        !           432: 
        !           433: /*
        !           434:  * Free all storage in the event and breakpoint tables.
        !           435:  */
        !           436: 
        !           437: public bpfree()
        !           438: {
        !           439:     register Event e;
        !           440: 
        !           441:     fixbps();
        !           442:     foreach (Event, e, eventlist)
        !           443:        delevent(e->id);
        !           444:        list_delete(list_curitem(eventlist), eventlist);
        !           445:     endfor
        !           446: }
        !           447: 
        !           448: /*
        !           449:  * Determine if the program stopped at a known breakpoint
        !           450:  * and if so do the associated commands.
        !           451:  */
        !           452: 
        !           453: public Boolean bpact()
        !           454: {
        !           455:     register Breakpoint p;
        !           456:     Boolean found;
        !           457: 
        !           458:     found = false;
        !           459:     foreach (Breakpoint, p, bplist)
        !           460:        if (p->bpaddr == pc) {
        !           461:            if (tracebpts) {
        !           462:                printf("breakpoint found at location 0x%x\n", pc);
        !           463:            }
        !           464:            found = true;
        !           465:            if (p->event->temporary) {
        !           466:                delevent(p->event->id);
        !           467:            }
        !           468:            evalcmdlist(p->actions);
        !           469:        }
        !           470:     endfor
        !           471:     if (isstopped) {
        !           472:        printstatus();
        !           473:     }
        !           474:     fflush(stdout);
        !           475:     return found;
        !           476: }
        !           477: 
        !           478: /*
        !           479:  * Begin single stepping and executing the given commands after each step.
        !           480:  * If the first argument is true step by instructions, otherwise
        !           481:  * step by source lines.
        !           482:  *
        !           483:  * We automatically set a breakpoint at the end of the current procedure
        !           484:  * to turn off the given tracing.
        !           485:  */
        !           486: 
        !           487: public traceon(inst, event, cmdlist)
        !           488: Boolean inst;
        !           489: Event event;
        !           490: Cmdlist cmdlist;
        !           491: {
        !           492:     register Trcmd trcmd;
        !           493:     Breakpoint bp;
        !           494:     Node until;
        !           495:     Cmdlist actions;
        !           496:     Address ret;
        !           497: 
        !           498:     trcmd = new(Trcmd);
        !           499:     ++trid;
        !           500:     trcmd->trid = trid;
        !           501:     trcmd->event = event;
        !           502:     trcmd->cmdlist = cmdlist;
        !           503:     single_stepping = true;
        !           504:     if (inst) {
        !           505:        inst_tracing = true;
        !           506:        list_append(list_item(trcmd), nil, eachinst);
        !           507:     } else {
        !           508:        list_append(list_item(trcmd), nil, eachline);
        !           509:     }
        !           510:     ret = return_addr();
        !           511:     if (ret != 0) {
        !           512:        until = build(O_EQ, build(O_SYM, pcsym), build(O_LCON, ret));
        !           513:        actions = buildcmdlist(build(O_TRACEOFF, trcmd->trid));
        !           514:        event_once(until, actions);
        !           515:     }
        !           516:     if (tracebpts) {
        !           517:        printf("adding trace %d for event %d\n", trcmd->trid, event->id);
        !           518:     }
        !           519: }
        !           520: 
        !           521: /*
        !           522:  * Turn off some kind of tracing.
        !           523:  * Strictly an internal command, this cannot be invoked by the user.
        !           524:  */
        !           525: 
        !           526: public traceoff(id)
        !           527: Integer id;
        !           528: {
        !           529:     register Trcmd t;
        !           530:     register Boolean found;
        !           531: 
        !           532:     found = false;
        !           533:     foreach (Trcmd, t, eachline)
        !           534:        if (t->trid == id) {
        !           535:            printrmtr(t);
        !           536:            list_delete(list_curitem(eachline), eachline);
        !           537:            found = true;
        !           538:            break;
        !           539:        }
        !           540:     endfor
        !           541:     if (not found) {
        !           542:        foreach (Trcmd, t, eachinst)
        !           543:            if (t->event->id == id) {
        !           544:                printrmtr(t);
        !           545:                list_delete(list_curitem(eachinst), eachinst);
        !           546:                found = true;
        !           547:                break;
        !           548:            }
        !           549:        endfor
        !           550:        if (not found) {
        !           551:            panic("missing trid %d", id);
        !           552:        }
        !           553:     }
        !           554:     if (list_size(eachinst) == 0) {
        !           555:        inst_tracing = false;
        !           556:        if (list_size(eachline) == 0) {
        !           557:            single_stepping = false;
        !           558:        }
        !           559:     }
        !           560: }
        !           561: 
        !           562: /*
        !           563:  * If breakpoints are being traced, note that a Trcmd is being deleted.
        !           564:  */
        !           565: 
        !           566: private printrmtr(t)
        !           567: Trcmd t;
        !           568: {
        !           569:     if (tracebpts) {
        !           570:        printf("removing trace %d", t->trid);
        !           571:        if (t->event != nil) {
        !           572:            printf(" for event %d", t->event->id);
        !           573:        }
        !           574:        printf("\n");
        !           575:     }
        !           576: }
        !           577: 
        !           578: /*
        !           579:  * Print out news during single step tracing.
        !           580:  */
        !           581: 
        !           582: public printnews()
        !           583: {
        !           584:     register Trcmd t;
        !           585: 
        !           586:     foreach (Trcmd, t, eachline)
        !           587:        evalcmdlist(t->cmdlist);
        !           588:     endfor
        !           589:     foreach (Trcmd, t, eachinst)
        !           590:        evalcmdlist(t->cmdlist);
        !           591:     endfor
        !           592:     bpact();
        !           593: }
        !           594: 
        !           595: /*
        !           596:  * A procedure call/return has occurred while single-stepping,
        !           597:  * note it if we're tracing lines.
        !           598:  */
        !           599: 
        !           600: private Boolean chklist();
        !           601: 
        !           602: public callnews(iscall)
        !           603: Boolean iscall;
        !           604: {
        !           605:     if (not chklist(eachline, iscall)) {
        !           606:        chklist(eachinst, iscall);
        !           607:     }
        !           608: }
        !           609: 
        !           610: private Boolean chklist(list, iscall)
        !           611: List list;
        !           612: Boolean iscall;
        !           613: {
        !           614:     register Trcmd t;
        !           615:     register Command cmd;
        !           616: 
        !           617:     curfunc = whatblock(pc);
        !           618:     foreach (Trcmd, t, list)
        !           619:        foreach (Command, cmd, t->cmdlist)
        !           620:            if (cmd->op == O_PRINTSRCPOS and
        !           621:              (cmd->value.arg[0] == nil or cmd->value.arg[0]->op == O_QLINE)) {
        !           622:                if (iscall) {
        !           623:                    printentry(curfunc);
        !           624:                } else {
        !           625:                    printexit(curfunc);
        !           626:                }
        !           627:                return true;
        !           628:            }
        !           629:        endfor
        !           630:     endfor
        !           631:     return false;
        !           632: }
        !           633: 
        !           634: /*
        !           635:  * When tracing variables we keep a copy of their most recent value
        !           636:  * and compare it to the current one each time a breakpoint occurs.
        !           637:  * MAXTRSIZE is the maximum size variable we allow.
        !           638:  */
        !           639: 
        !           640: #define MAXTRSIZE 512
        !           641: 
        !           642: /*
        !           643:  * List of variables being watched.
        !           644:  */
        !           645: 
        !           646: typedef struct Trinfo *Trinfo;
        !           647: 
        !           648: struct Trinfo {
        !           649:     Node variable;
        !           650:     Address traddr;
        !           651:     Symbol trblock;
        !           652:     char *trvalue;
        !           653: };
        !           654: 
        !           655: private List trinfolist;
        !           656: 
        !           657: /*
        !           658:  * Find the trace information record associated with the given record.
        !           659:  * If there isn't one then create it and add it to the list.
        !           660:  */
        !           661: 
        !           662: private Trinfo findtrinfo(p)
        !           663: Node p;
        !           664: {
        !           665:     register Trinfo tp;
        !           666:     Boolean isnew;
        !           667: 
        !           668:     isnew = true;
        !           669:     if (trinfolist == nil) {
        !           670:        trinfolist = list_alloc();
        !           671:     } else {
        !           672:        foreach (Trinfo, tp, trinfolist)
        !           673:            if (tp->variable == p) {
        !           674:                isnew = false;
        !           675:                break;
        !           676:            }
        !           677:        endfor
        !           678:     }
        !           679:     if (isnew) {
        !           680:        if (tracebpts) {
        !           681:            printf("adding trinfo for \"");
        !           682:            prtree(stdout, p);
        !           683:            printf("\"\n");
        !           684:        }
        !           685:        tp = new(Trinfo);
        !           686:        tp->variable = p;
        !           687:        tp->traddr = lval(p);
        !           688:        tp->trvalue = nil;
        !           689:        list_append(list_item(tp), nil, trinfolist);
        !           690:     }
        !           691:     return tp;
        !           692: }
        !           693: 
        !           694: /*
        !           695:  * Print out the value of a variable if it has changed since the
        !           696:  * last time we checked.
        !           697:  */
        !           698: 
        !           699: public printifchanged(p)
        !           700: Node p;
        !           701: {
        !           702:     register Trinfo tp;
        !           703:     register int n;
        !           704:     char buff[MAXTRSIZE];
        !           705:     static Lineno prevline;
        !           706: 
        !           707:     tp = findtrinfo(p);
        !           708:     n = size(p->nodetype);
        !           709:     dread(buff, tp->traddr, n);
        !           710:     if (tp->trvalue == nil) {
        !           711:        tp->trvalue = newarr(char, n);
        !           712:        mov(buff, tp->trvalue, n);
        !           713:        mov(buff, sp, n);
        !           714:        sp += n;
        !           715:        printf("initially (at line %d):\t", curline);
        !           716:        prtree(stdout, p);
        !           717:        printf(" = ");
        !           718:        printval(p->nodetype);
        !           719:        putchar('\n');
        !           720:     } else if (cmp(tp->trvalue, buff, n) != 0) {
        !           721:        mov(buff, tp->trvalue, n);
        !           722:        mov(buff, sp, n);
        !           723:        sp += n;
        !           724:        printf("after line %d:\t", prevline);
        !           725:        prtree(stdout, p);
        !           726:        printf(" = ");
        !           727:        printval(p->nodetype);
        !           728:        putchar('\n');
        !           729:     }
        !           730:     prevline = curline;
        !           731: }
        !           732: 
        !           733: /*
        !           734:  * Stop if the value of the given expression has changed.
        !           735:  */
        !           736: 
        !           737: public stopifchanged(p)
        !           738: Node p;
        !           739: {
        !           740:     register Trinfo tp;
        !           741:     register int n;
        !           742:     char buff[MAXTRSIZE];
        !           743:     static Lineno prevline;
        !           744: 
        !           745:     tp = findtrinfo(p);
        !           746:     n = size(p->nodetype);
        !           747:     dread(buff, tp->traddr, n);
        !           748:     if (tp->trvalue == nil) {
        !           749:        tp->trvalue = newarr(char, n);
        !           750:        mov(buff, tp->trvalue, n);
        !           751:        isstopped = true;
        !           752:     } else if (cmp(tp->trvalue, buff, n) != 0) {
        !           753:        mov(buff, tp->trvalue, n);
        !           754:        isstopped = true;
        !           755:     }
        !           756:     prevline = curline;
        !           757: }
        !           758: 
        !           759: /*
        !           760:  * Free the tracing table.
        !           761:  */
        !           762: 
        !           763: public trfree()
        !           764: {
        !           765:     register Trinfo tp;
        !           766: 
        !           767:     foreach (Trinfo, tp, trinfolist)
        !           768:        dispose(tp->trvalue);
        !           769:        dispose(tp);
        !           770:        list_delete(list_curitem(trinfolist), trinfolist);
        !           771:     endfor
        !           772: }
        !           773: 
        !           774: /*
        !           775:  * Fix up breakpoint information before continuing execution.
        !           776:  *
        !           777:  * It's necessary to destroy events and breakpoints that were created
        !           778:  * temporarily and still exist because the program terminated abnormally.
        !           779:  */
        !           780: 
        !           781: public fixbps()
        !           782: {
        !           783:     register Event e;
        !           784:     register Trcmd t;
        !           785: 
        !           786:     single_stepping = false;
        !           787:     inst_tracing = false;
        !           788:     trfree();
        !           789:     foreach (Event, e, eventlist)
        !           790:        if (e->temporary) {
        !           791:            delevent(e->id);
        !           792:        }
        !           793:     endfor
        !           794:     foreach (Trcmd, t, eachline)
        !           795:        printrmtr(t);
        !           796:        list_delete(list_curitem(eachline), eachline);
        !           797:     endfor
        !           798:     foreach (Trcmd, t, eachinst)
        !           799:        printrmtr(t);
        !           800:        list_delete(list_curitem(eachinst), eachinst);
        !           801:     endfor
        !           802: }
        !           803: 
        !           804: /*
        !           805:  * Set all breakpoints in object code.
        !           806:  */
        !           807: 
        !           808: public setallbps()
        !           809: {
        !           810:     register Breakpoint p;
        !           811: 
        !           812:     foreach (Breakpoint, p, bplist)
        !           813:        setbp(p->bpaddr);
        !           814:     endfor
        !           815: }
        !           816: 
        !           817: /*
        !           818:  * Undo damage done by "setallbps".
        !           819:  */
        !           820: 
        !           821: public unsetallbps()
        !           822: {
        !           823:     register Breakpoint p;
        !           824: 
        !           825:     foreach (Breakpoint, p, bplist)
        !           826:        unsetbp(p->bpaddr);
        !           827:     endfor
        !           828: }

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