tcl-debug.ps

Linux下的tcl语言调试器

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612 792 0 FMBEGINPAGE
0 12 Q
0 X
0 K
(T) 72 27 T
(cl/Tk W) 78.9 27 T
(orkshop - June 10-1) 119.89 27 T
(1, 1993 - Berkeley) 220.85 27 T
(, CA) 311.46 27 T
1 10 Q
(3) 553 27 T
0 18 Q
(Intr) 72 177.67 T
(oduction) 102.65 177.67 T
1 12 Q
0.48 (T) 72 156.67 P
0.48 (cl [1][2] is a language speci\336cally intended for) 78.49 156.67 P
2.75 (generic application control.  In some applica-) 72 142.67 P
6.1 (tions it dominates the user) 72 128.67 P
6.1 (\325) 222.76 128.67 P
6.1 (s view of the) 226.09 128.67 P
0.56 (application.  Expect [3][4] is a good example of) 72 114.67 P
0.81 (this.  Expect is always executing T) 72 100.67 P
0.81 (cl statements) 242.9 100.67 P
1.46 (\320 usually from a script.  When the script ends,) 72 86.67 P
(Expect ends.) 72 72.67 T
1.37 (This type of application is common.  W) 324 157.83 P
1.37 (ith this) 523.64 157.83 P
1.07 (heavy reliance on T) 324 143.83 P
1.07 (cl, it is useful to have a de-) 421.28 143.83 P
2.76 (bugger that understands T) 324 129.83 P
2.76 (cl.  For example, it) 456.35 129.83 P
0.77 (should be able to single-step and print values at) 324 115.83 P
(user discretion.) 324 101.83 T
0.59 (The debugger described herein works in exactly) 324 82.83 P
2.15 (this way) 324 68.83 P
2.15 (.  It works best with applications like) 365.69 68.83 P
126 225 504 684 R
7 X
V
0 24 Q
0 X
(A Debugger for T) 148.87 668 T
(cl Applications) 328.53 668 T
2 14 Q
(Don Libes) 286.04 632.67 T
1 F
(National Institute of Standards and T) 182.77 611.67 T
(echnology) 388.93 611.67 T
2 F
(Abstract) 291.29 548.67 T
1 12 Q
0.51 (T) 126 529 P
0.51 (cl is a language speci\336cally intended for generic application control.  By us-) 132.49 529 P
2.79 (ing it, application programmers escape the dilemma of whether to design) 126 515 P
2.36 (sophisticated application-speci\336c languages or whether to build tools more) 126 501 P
0.5 (quickly but that are limited in \337exibility) 126 487 P
0.5 (.  T) 320.13 487 P
0.5 (cl is easy for application program-) 336.62 487 P
0.49 (mers to use, however) 126 473 P
0.49 (, up to now) 228.91 473 P
0.49 (, there has been no general-purpose debugger) 283.58 473 P
(for application users.) 126 459 T
1.88 (This paper describes an implementation of a debugger for T) 126 440 P
1.88 (cl applications.) 429.5 440 P
1.02 (The debugger has a typical front-end but with some extremely unusual com-) 126 426 P
0.37 (mands, in part because of the features and limitations of T) 126 412 P
0.37 (cl.  The debugger is) 407.61 412 P
1.47 (modeless, allowing users to issue T) 126 398 P
1.47 (cl and application commands along with) 302.42 398 P
0.58 (debugger commands.  Each type of command may invoke the other) 126 384 P
0.58 (, allowing) 455.44 384 P
(debugging to be programmed, dynamically or in advance.) 126 370 T
0.43 (The debugger is written in C and is very fast.  When linked in but not used, it) 126 351 P
0.99 (does not slow applications at all.  The debugger requires no modi\336cations to) 126 337 P
(the T) 126 323 T
(cl core, and can be plugged into applications with little ef) 150.14 323 T
(fort.) 425.4 323 T
(Keywords: T) 126 285 T
(cl, Tk, T) 188.11 285 T
(ool Command Language, Expect, debugger) 228.58 285 T
(, interpreter) 436.62 285 T
2 F
0.57 (Reprinted fr) 126 247 P
0.57 (om Pr) 184.42 247 P
0.57 (oceedings of the 1993 T) 214.2 247 P
0.57 (cl/Tk W) 329.96 247 P
0.57 (orkshop, Berkeley) 366.4 247 P
0.57 (, CA, June) 452.9 247 P
(10-1) 126 233 T
(1, 1993.) 147.1 233 T
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612 792 0 FMBEGINPAGE
0 12 Q
0 X
0 K
(A Debugger for T) 54 758.33 T
(cl Applications) 143.83 758.33 T
(Don Libes) 487.68 758.33 T
1 10 Q
(4) 54 27 T
0 12 Q
(T) 277.22 27 T
(cl/Tk W) 284.12 27 T
(orkshop - June 10-1) 325.11 27 T
(1, 1993 - Berkeley) 426.08 27 T
(, CA) 516.68 27 T
1 F
0.6 (Expect that sequentially execute T) 54 730 P
0.6 (cl commands,) 220.77 730 P
0.81 (although it can also be used with any T) 54 716 P
0.81 (cl appli-) 247.55 716 P
(cation.) 54 702 T
2.39 (This paper has three parts.  The \336rst part de-) 54 683 P
-0.12 (scribes the debugger in terms of how it is used in) 54 669 P
-0.08 (a typical application.   The second part of the pa-) 54 655 P
8.03 (per describes how the debugger can be) 54 641 P
1.48 (integrated into T) 54 627 P
1.48 (cl applications.  The third part) 136.06 627 P
1.36 (describes the design and implementation of the) 54 613 P
(debugger) 54 599 T
(.) 97.97 599 T
0 18 Q
(V) 54 567 T
(iew by the Application User) 66.32 567 T
1 12 Q
1.35 (This section of the paper is a debugger tutorial) 54 546 P
1.34 (which shows the application user) 54 532 P
1.34 (\325) 219.02 532 P
1.34 (s view of the) 222.36 532 P
0.84 (debugger) 54 518 P
0.84 (.  For the sake of concreteness, Expect) 97.97 518 P
2.08 ([1] will be used as the application.  However) 54 504 P
2.08 (,) 285 504 P
2.8 (any other application using the debugger will) 54 490 P
(work similarly) 54 476 T
(.) 123.51 476 T
0 F
(Starting the Debugger) 54 454 T
1 F
0.93 (The debugger is initially invoked in an applica-) 54 435 P
0.75 (tion-dependent way) 54 421 P
0.75 (.  In Expect, the debugger is) 148.9 421 P
(started by using the \337ag \322-D 1\323.  For example:) 54 407 T
3 11 Q
(% expect -D 1 script) 72 388.67 T
1 12 Q
2.78 (If the system supports the #! mechanism, the) 54 374 P
(script may also be started as:) 54 360 T
3 11 Q
(% script -D 1) 72 341.67 T
1 12 Q
0.25 (In either case, additional ar) 54 327 P
0.25 (guments may be sup-) 184.99 327 P
(plied as usual.) 54 313 T
1.72 (The user is prompted for a command.  At this) 54 294 P
1.73 (point either Expect commands, T) 54 280 P
1.73 (cl commands,) 219.65 280 P
0.48 (or debugger commands may be entered.  This is) 54 266 P
-0.25 (true at all other times that the user is prompted as) 54 252 P
(well.  The debugger is modeless.) 54 238 T
1.5 (The following T) 54 219 P
1.5 (cl commands illustrate that the) 134.77 219 P
(debugger evaluates T) 54 205 T
(cl commands as usual.) 155.74 205 T
3 11 Q
(expect2.1> set m {a b c}) 72 186.67 T
(a b c) 72 175.67 T
(expect2.2> llength $m) 72 164.67 T
(3) 72 153.67 T
(expect2.3>) 72 142.67 T
1 12 Q
1.21 (The command prompt is changeable by the ap-) 54 128 P
-0.09 (plication or user) 54 114 P
-0.09 (.  Here, the second number is the) 131.1 114 P
2.41 (T) 54 100 P
2.41 (cl history identi\336er) 60.49 100 P
2.41 (.  The \336rst number is the) 155.93 100 P
(depth of the evaluation stack.) 54 86 T
0.51 (In the context of a script, the initial depth of the) 306 730 P
0.02 (evaluation stack is 1 but the debugger always in-) 306 716 P
0.02 (troduces a new level to the stack.  Hence, we see) 306 702 P
(a \3222\323 in the prompt.) 306 688 T
0.54 (Expect also allows the application to take initial) 306 669 P
1.31 (control.  By using the \337ag \322-D 0\323, the applica-) 306 655 P
0.39 (tion runs until the user presses ^C at which time) 306 641 P
0.69 (the debugger begins running.  The remainder of) 306 627 P
1.97 (this tutorial will assume that the debugger has) 306 613 P
(started up immediately from the \337ag \322-D 1\323.) 306 599 T
0 F
(Command Overview and Philosophy) 306 577 T
1 F
(The debugger commands are:) 306 558 T
352.64 537.69 324 537.69 2 L
V
0.59 H
0 Z
N
(Name) 324 539 T
424.96 537.69 369 537.69 2 L
V
N
(Description) 369 539 T
(s) 338.11 523 T
(step into procedure) 369 523 T
(n) 338.11 508 T
(step over procedure) 369 508 T
(r) 338.11 493 T
(return from procedure) 369 493 T
(b) 338.11 478 T
(set, clear) 369 478 T
(, or show breakpoint) 411.14 478 T
(c) 338.11 463 T
(continue) 369 463 T
(w) 338.11 448 T
(show stack) 369 448 T
(u) 338.11 433 T
(move scope up) 369 433 T
(d) 338.11 418 T
(move scope down) 369 418 T
(h) 338.11 403 T
(help) 369 403 T
0.12 (The debugger commands are all one letter) 306 386 P
0.12 (. Short) 507.89 386 P
0.7 (procedure names are desirable in an interactive-) 306 372 P
1.31 (only application such as the debugger) 306 358 P
1.31 (.  In con-) 492.77 358 P
1.9 (trast, scripted applications rarely use one-letter) 306 344 P
2.03 (commands.  The chances of name con\337ict be-) 306 330 P
0.03 (tween the debugger and scripted applications are) 306 316 P
(very low) 306 302 T
(.) 347.52 302 T
2.5 (The command names are very similar and, in) 306 283 P
0.19 (some cases, identical to other popular debuggers) 306 269 P
0.54 (\050gdb, dbx, etc.\051.  Existing T) 306 255 P
0.54 (cl procedures are di-) 440.13 255 P
0.23 (rectly usable so there are no new commands, for) 306 241 P
-0.14 (example, to print variables since T) 306 227 P
-0.14 (cl already pro-) 470.35 227 P
2.58 (vides such commands \050e.g., set, puts, parray\051.) 306 213 P
1.76 (The intent of the debugger is that it should be) 306 199 P
0.83 (easy to learn and use, and otherwise stay out of) 306 185 P
(the way) 306 171 T
(.) 342.86 171 T
0.03 (The debugger uses the application\325) 306 152 P
0.03 (s top-level in-) 473.32 152 P
0.47 (teractor) 306 138 P
0.47 (.  In the case of Expect, for example, the) 341.97 138 P
-0.03 (debugger uses Expect\325) 306 124 P
-0.03 (s interact command which) 413.85 124 P
(prompts for commands and evaluates them.) 306 110 T
3.8 (For the purposes of describing the debugger) 306 91 P
0.02 (commands, the following script is assumed to be) 306 77 P
2.34 (named) 306 63 P
2 F
2.34 (debug-test.exp) 343.31 63 P
1 F
2.34 (.) 412.92 63 P
1 10 Q
1.95 (1) 415.92 67.8 P
1 12 Q
2.34 (  The script doesn\325) 420.92 63 P
2.34 (t do) 519.33 63 P
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612 792 0 FMBEGINPAGE
0 12 Q
0 X
0 K
(Don Libes) 72 758.33 T
(A Debugger for T) 391.87 758.33 T
(cl Applications) 481.7 758.33 T
(T) 72 27 T
(cl/Tk W) 78.9 27 T
(orkshop - June 10-1) 119.89 27 T
(1, 1993 - Berkeley) 220.85 27 T
(, CA) 311.46 27 T
1 10 Q
(5) 553 27 T
1 12 Q
2.4 (anything useful.  It merely serves to illustrate) 72 730 P
(how the debugger is used.) 72 716 T
3 11 Q
(set b 1) 90 697.67 T
(proc p4 {x} {) 90 675.67 T
(return [) 126 664.67 T
(    expr 5+[expr 1+$x]]) 126 653.67 T
(}) 90 642.67 T
(set z [) 90 620.67 T
(   expr 1+[expr 2+[p4 $b]]) 90 609.67 T
(]) 90 598.67 T
(proc p3 {} {) 90 576.67 T
(set m 0) 126 565.67 T
(}) 90 554.67 T
(proc p2 {} {) 90 532.67 T
(set c 4) 126 521.67 T
(p3) 126 510.67 T
(set d 5) 126 499.67 T
(}) 90 488.67 T
(proc p1 {} {) 90 466.67 T
(set a 2) 126 455.67 T
(p2) 126 444.67 T
(set a 3) 126 433.67 T
(set a 5) 126 422.67 T
(}) 90 411.67 T
(p1) 90 389.67 T
(set k 7) 90 378.67 T
(p1) 90 367.67 T
1 12 Q
0.43 (If the debugger is started at the beginning of the) 72 353 P
2.1 (script, no statements have been executed.  T) 72 339 P
2.1 (cl) 297.34 339 P
(and application commands have global scope.) 72 325 T
3 11 Q
(% expect -D 1 debug-test.exp) 90 306.67 T
(1: set b 1) 90 295.67 T
(expect2.1>) 90 284.67 T
1 12 Q
0.98 (When a new command is about to be executed,) 72 270 P
-0.02 (the debugger prints the command.  It is preceded) 72 256 P
1.78 (by the evaluation stack level.  \322set b 1\323 is the) 72 242 P
-0.05 (\336rst line in the script.  It has not yet been execut-) 72 228 P
(ed.  \322info exists\323 con\336rms this.) 72 214 T
3 11 Q
(expect2.1> info exists b) 90 195.67 T
(0) 90 184.67 T
0 14 Q
(The \322n\323 command \320 \322Next\323) 72 161.67 T
1 12 Q
0.36 (The) 72 142 P
2 F
0.36 (n) 94.01 142 P
1 F
0.36 ( command executes the pending command) 100.01 142 P
1.26 (\320 in this case \322set b 1\323 \320 and displays the next) 72 128 P
(command to be executed.) 72 114 T
3 11 Q
(expect2.2> n) 90 95.67 T
(1: proc p4 {} {) 90 84.67 T
72 66 306 81 C
81 79 225 79 2 L
0.5 H
2 Z
0 X
0 K
N
0 0 612 792 C
1 10 Q
0 X
0 K
(1. Italics indicate something being de\336ned.) 90 59.33 T
3 11 Q
(return [) 378 730.67 T
(expr 5+[expr 1+$x]]) 414 719.67 T
(}) 342 708.67 T
(expect2.3> info exists b) 342 697.67 T
(1) 342 686.67 T
1 12 Q
-0.15 (The command \322info exists b\323 con\336rms that b has) 324 672 P
1.58 (been set.  The procedure p4 is about to be de-) 324 658 P
(\336ned.) 324 644 T
3 11 Q
(expect2.4> n) 342 625.67 T
(4: p4 $b) 342 614.67 T
(expect5.5>) 342 603.67 T
1 12 Q
1.9 (The procedure p4 has now been de\336ned.  The) 324 589 P
0.32 (next command to be executed is p4 itself.  It ap-) 324 575 P
(pears in the statement:) 324 561 T
3 11 Q
(set z [) 342 542.67 T
(expr 1+[expr 2+[p4 $b]]) 378 531.67 T
(]) 342 520.67 T
1 12 Q
0.11 (The three sets of braces introduce three new lev-) 324 506 P
0.23 (els on the evaluation stack, hence the stack level) 324 492 P
0.62 (in which p4 is about to be executed is shown as) 324 478 P
(\3224\323.) 324 464 T
1 10 Q
(1) 343.64 468.8 T
1 12 Q
1.88 (Notice that the evaluation stack level does not) 324 445 P
2.22 (af) 324 431 P
2.22 (fect the scope.  W) 333.1 431 P
2.22 (e are still in the top-level) 427.3 431 P
(scope and b is still visible.) 324 417 T
3 11 Q
(expect5.5> info exists b) 342 398.67 T
(1) 342 387.67 T
1 12 Q
0.4 (The ar) 324 373 P
0.4 (gument to p4 is $b.  The value of this can) 355.15 373 P
(be evaluated by using set or puts.) 324 359 T
3 11 Q
(expect5.6> set b) 342 340.67 T
(1) 342 329.67 T
(expect5.7> puts $b) 342 318.67 T
(1) 342 307.67 T
1 12 Q
2.19 (Another n command executes p4, popping the) 324 293 P
0.21 (stack one level.  Additional n commands contin-) 324 279 P
0.15 (ue evaluation of the \322set z\323 command, each time) 324 265 P
(popping the stack one level.) 324 251 T
3 11 Q
(expect5.8> n) 342 232.67 T
(3: expr 2+[p4 $b]) 342 221.67 T
(expect4.9> n) 342 210.67 T
(2: expr 1+[expr 2+[p4 $b]]) 342 199.67 T
(expect3.10> n) 342 188.67 T
(1: set z [) 342 177.67 T
(expr 1+[expr 2+[p4 $b]]) 378 166.67 T
(]) 342 155.67 T
(expect2.11>) 342 144.67 T
324 90 558 105 C
333 103 477 103 2 L
0.5 H
2 Z
0 X
0 K
N
0 0 612 792 C
1 10 Q
0 X
0 K
0.85 (1. Whether the word \322stack\323 refers to procedure) 342 83.33 P
2.31 (call stack or evaluation stack should either be) 342 71.33 P
(explicit or clearly implied by context.) 342 59.33 T
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612 792 0 FMBEGINPAGE
0 12 Q
0 X
0 K
(A Debugger for T) 54 758.33 T
(cl Applications) 143.83 758.33 T
(Don Libes) 487.68 758.33 T