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1.1 root 1: .\" Copyright (c) 1983, 1990 The Regents of the University of California.
2: .\" All rights reserved.
3: .\"
4: .\" Redistribution and use in source and binary forms are permitted provided
5: .\" that: (1) source distributions retain this entire copyright notice and
6: .\" comment, and (2) distributions including binaries display the following
7: .\" acknowledgement: ``This product includes software developed by the
8: .\" University of California, Berkeley and its contributors'' in the
9: .\" documentation or other materials provided with the distribution and in
10: .\" all advertising materials mentioning features or use of this software.
11: .\" Neither the name of the University nor the names of its contributors may
12: .\" be used to endorse or promote products derived from this software without
13: .\" specific prior written permission.
14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17: .\"
18: .\" @(#)dbx.1 6.5 (Berkeley) 7/24/90
19: .\"
20: .Dd July 24, 1990
21: .Dt DBX 1
22: .Os BSD 4.2
23: .Sh NAME
24: .Nm dbx
25: .Nd debugger
26: .Sh SYNOPSIS
27: .Nm Dbx
28: .Op Fl r
29: .Op Fl i
30: .Op Fl k
31: .Op Fl I Ar dir
32: .Op Fl c Ar file
33: .Op Ar objfile Op Ar coredump
34: .Sh DESCRIPTION
35: .Nm Dbx
36: is a tool for source level debugging and execution of
37: programs under UNIX.
38: The
39: .Ar objfile
40: is an object file produced by a compiler
41: with the appropriate flag (usually
42: .Fl g )
43: specified to produce symbol information in the object file.
44: Currently,
45: .Xr cc 1 ,
46: .Xr f77 1 ,
47: .Xr pc 1 ,
48: and the DEC Western
49: Research Laboratory Modula-2 compiler,
50: .Xr mod l ,
51: produce the appropriate source information.
52: The machine level facilities of
53: .Nm dbx
54: can be used on any program.
55: .Pp
56: The object file contains a symbol table that includes the names of
57: all the source files translated by the compiler to create it.
58: These files are available for perusal while using the debugger.
59: .Pp
60: If a file named
61: .Pa core
62: exists in the current directory
63: or a
64: .Ar coredump
65: file is specified,
66: .Nm dbx
67: can be used
68: to examine the state of the program when it faulted.
69: .Pp
70: If the file
71: .Pa .dbxinit
72: exists in the current directory then the
73: debugger commands in it are executed.
74: .Nm Dbx
75: also checks for a
76: .Pa .dbxinit
77: in the user's home directory
78: if there isn't one in the current directory.
79: .Pp
80: The command line options and their meanings are:
81: .Tw Fl
82: .Tp Fl r
83: Execute
84: .Ar objfile
85: immediately.
86: If it terminates successfully
87: .Nm dbx
88: exits.
89: Otherwise the reason for termination will be reported
90: and the user offered the option of entering the debugger
91: or letting the program fault.
92: .Nm Dbx
93: will read from
94: .Pa /dev/tty
95: when
96: .Fl r
97: is specified
98: and standard input is not a terminal.
99: .Tp Fl i
100: Force
101: .Nm dbx
102: to act as though standard input is a terminal.
103: .Tp Fl k
104: Map memory addresses, useful for kernel debugging.
105: .Tp Cx Fl I
106: .Cx \&\ \&
107: .Ar dir
108: .Cx
109: Add
110: .Ar dir
111: to the list of directories
112: that are searched when looking for a source file.
113: Normally
114: .Nm dbx
115: looks for source files in the current directory
116: and in the directory where
117: .Ar objfile
118: is located.
119: The directory search path can also be set with the
120: .Ic use
121: command.
122: .Tp Cx Fl c
123: .Cx \&\ \&
124: .Ar file
125: .Cx
126: Execute the
127: .Nm dbx
128: commands in the
129: .Ar file
130: before
131: reading from standard input.
132: .Tp
133: .Pp
134: Unless
135: .Fl r
136: is specified,
137: .Nm dbx
138: just prompts and waits for a command.
139: .Ss Execution and Tracing Commands
140: .Dw Fl
141: .Di L
142: .Dp Cx Ic run
143: .Cx \&\ \&
144: .Op Ar args
145: .Cx \&\ \&
146: .Op Sy < Ar filename
147: .Cx \&\ \&
148: .Op Sy > Ar filename
149: .Cx
150: .Dp Cx Ic rerun
151: .Cx \&\ \&
152: .Op Ar args
153: .Cx \&\ \&
154: .Op Sy < Ar filename
155: .Cx \&\ \&
156: .Op Sy > Ar filename
157: .Cx
158: Start executing
159: .Ar objfile ,
160: passing
161: .Ar args
162: as command line arguments;
163: .Sy <
164: or
165: .Sy >
166: can be used to redirect input or output in the usual manner.
167: When
168: .Ic rerun
169: is used without any arguments the previous
170: argument list is passed to the program;
171: otherwise it is identical to
172: .Ic run .
173: If
174: .Ar objfile
175: has been written since the last time the symbolic information
176: was read in,
177: .Nm dbx
178: will read in the new information.
179: .Dp Cx Ic trace
180: .Cx \&\ \&
181: .Op Ic in Ar procedure/function
182: .Cx \&\ \&
183: .Op Ic if Ar condition
184: .Cx
185: .Dp Cx Ic trace
186: .Cx \&\ \&
187: .Ar source-line-number
188: .Cx \&\ \&
189: .Op Ic if Ar condition
190: .Cx
191: .Dp Cx Ic trace
192: .Cx \&\ \&
193: .Ar procedure/function
194: .Cx \&\ \&
195: .Op Ic in Ar procedure/function
196: .Cx \&\ \&
197: .Op Ic if Ar condition
198: .Cx
199: .Dp Cx Ic trace
200: .Cx \&\ \&
201: .Ar expression
202: .Cx \&\ \&
203: .Ic at
204: .Cx \&\ \&
205: .Ar source-line-number
206: .Cx \&\ \&
207: .Op Ic if Ar condition
208: .Cx
209: .Dp Cx Ic trace
210: .Cx \&\ \&
211: .Ar variable
212: .Cx \&\ \&
213: .Op Ic in Ar procedure/function
214: .Cx \&\ \&
215: .Op Ic if Ar condition
216: .Cx
217: Have tracing information printed when the program is executed.
218: A number is associated with the command that is used
219: to turn the tracing off (see the
220: .Ic delete
221: command).
222: .Pp
223: The first argument describes what is to be traced.
224: If it is a
225: .Ar source-line-number ,
226: then the line is printed
227: immediately prior to being executed.
228: Source line numbers in a file other than the current one
229: must be preceded by the name of the file in quotes and a colon, e.g.
230: "mumble.p":17.
231: .Pp
232: If the argument is a procedure or function name then
233: every time it is called, information is printed telling
234: what routine called it, from what source line it was called,
235: and what parameters were passed to it.
236: In addition, its return is noted, and if it's a function
237: then the value it is returning is also printed.
238: .Pp
239: If the argument is an
240: .Ar expression
241: with an
242: .Ic at
243: clause
244: then the value of the expression is printed whenever the
245: identified source line is reached.
246: .Pp
247: If the argument is a variable then the name and value of the variable
248: is printed whenever it changes.
249: Execution is substantially slower during this form of tracing.
250: .Pp
251: If no argument is specified then all source lines are printed
252: before they are executed.
253: Execution is substantially slower during this form of tracing.
254: .Pp
255: The clause
256: .Ic in
257: .Ar procedure/function
258: restricts tracing information
259: to be printed only while executing inside the given procedure
260: or function.
261: .Pp
262: .Ar Condition
263: is a boolean expression and is
264: evaluated prior to printing the tracing information;
265: if it is false then the information is not printed.
266: .Dp Cx Ic stop if
267: .Cx \&\ \&
268: .Ar condition
269: .Cx
270: .Dp Cx Ic stop at
271: .Cx \&\ \&
272: .Ar source-line-number
273: .Cx \&\ \&
274: .Op Ic if Ar condition
275: .Cx
276: .Dp Cx Ic stop in
277: .Cx \&\ \&
278: .Ar source-line-number
279: .Cx \&\ \&
280: .Op Ic if Ar condition
281: .Cx
282: .Dp Cx Ic stop
283: .Cx \&\ \&
284: .Ar variable
285: .Cx \&\ \&
286: .Op Ic if Ar condition
287: .Cx
288: Stop execution when the given line is reached, procedure or function
289: called, variable changed, or condition true.
290: .Dp Cx Ic status
291: .Cx \&\ \&
292: .Op Ic \&> Ar filename
293: .Cx
294: Print out the currently active
295: .Ic trace
296: and
297: .Ic stop
298: commands.
299: .Dp Cx Ic delete
300: .Cx \&\ \&
301: .Ar command-number ...
302: .Cx
303: The traces or stops corresponding to the given numbers are removed.
304: The numbers associated with traces and stops are printed by
305: the
306: .Ic status
307: command.
308: .Dp Cx Ic catch
309: .Cx \&\ \&
310: .Ar number
311: .Cx
312: .Dp Cx Ic catch
313: .Cx \&\ \&
314: .Ar signal-name
315: .Cx
316: .Dp Cx Ic ignore
317: .Cx \&\ \&
318: .Ar number
319: .Cx
320: .Dp Cx Ic ignore
321: .Cx \&\ \&
322: .Ar signal-name
323: .Cx
324: Start or stop trapping a signal before it is sent
325: to the program.
326: This is useful when a program being debugged
327: handles signals such as interrupts.
328: A signal may be specified by number or by a name
329: (e.g., SIGINT).
330: Signal names are case insensitive and the ``SIG'' prefix is optional.
331: By default all signals are trapped except SIGCONT, SIGCHILD,
332: SIGALRM and SIGKILL.
333: .Dp Cx Ic cont
334: .Cx \&\ \&
335: .Ar integer
336: .Cx
337: .Dp Cx Ic cont
338: .Cx \&\ \&
339: .Ar signal-name
340: .Cx
341: Continue execution from where it stopped.
342: If a signal is specified, the process continues as though
343: it received the signal.
344: Otherwise, the process is continued as though it had not been stopped.
345: .Pp
346: Execution cannot be continued if the process has ``finished'',
347: that is, called the standard procedure ``exit''.
348: .Nm Dbx
349: does not allow the process to exit, thereby
350: letting the user to examine the program state.
351: .Dp Ic step
352: Execute one source line.
353: .Dp Ic next
354: Execute up to the next source line.
355: The difference between this and
356: .Ic step
357: is that
358: if the line contains a call to a procedure or function
359: the
360: .Ic step
361: command will stop at the beginning of that
362: block, while the
363: .Ic next
364: command will not.
365: .Dp Cx Ic return
366: .Cx \&\ \&
367: .Op Ar procedure
368: .Cx
369: Continue until a return to
370: .Ar procedure
371: is executed, or
372: until the current procedure returns if none is specified.
373: .Dp Cx Ic call
374: .Cx \&\ \&
375: .Ar procedure (parameters )
376: .Cx
377: Execute the object code associated with the named procedure or function.
378: .Dp
379: .Ss Printing Variables and Expressions
380: Names are resolved first using the static scope of the current function,
381: then using the dynamic scope if the name is not defined
382: in the static scope.
383: If static and dynamic searches do not yield a result,
384: an arbitrary symbol is chosen and
385: the message
386: .Dq Li [using Ar qualified name]
387: is printed.
388: The name resolution procedure may be overridden by qualifying an identifier
389: with a block name, e.g.,
390: .Dq Li module.variable
391: For C, source files are treated as modules named
392: by the file name without ``.c''.
393: .Pp
394: Expressions are specified with an approximately
395: common subset of C and Pascal (or equivalently Modula-2) syntax.
396: Indirection can be denoted using either a prefix ``*'' or
397: a postfix ``^'' and
398: array expressions are subscripted by brackets
399: .Cx (``
400: .Op
401: .Cx \'\').
402: .Cx
403: The field reference operator (``.'') can be used with pointers
404: as well as records, making the C operator ``\->'' unnecessary
405: (although it is supported).
406: .Pp
407: Types of expressions are checked;
408: the type of an expression may be overridden
409: by using
410: .Cx ``
411: .Ar type-name (expression)
412: .Cx \'\'.
413: .Cx
414: When there is no corresponding named type
415: the special constructs
416: .Cx ``&
417: .Ar type-name
418: .Cx \'\'
419: .Cx
420: and
421: .Cx ``$$
422: .Ar tag-name
423: .Cx \'\'
424: .Cx
425: can be used to represent a pointer to a named type or C structure tag.
426: .Dw Fl
427: .Di L
428: .Dp Cx Ic assign
429: .Cx \&\ \&
430: .Ar variable
431: .Ic =
432: .Ar expression
433: .Cx
434: Assign the value of the expression to the variable.
435: .Dp Cx Ic dump
436: .Cx \&\ \&
437: .Op Ar procedure
438: .Cx \&\ \&
439: .Op Ic > Ar filename
440: .Cx
441: Print the names and values of variables in the given procedure,
442: or the current one if none is specified.
443: If the procedure given is ``.'', then the all active variables
444: are dumped.
445: .Dp Cx Ic print
446: .Cx \&\ \&
447: .Ar expression
448: .Cx \&\ \&
449: .Op Ic \&, Ar expression ...
450: .Cx
451: Print out the values of the expressions.
452: .Dp Cx Ic whatis
453: .Cx \&\ \&
454: .Ar name
455: .Cx
456: Print the declaration of the given name, which may be qualified
457: with block names as above.
458: .Dp Cx Ic which
459: .Cx \&\ \&
460: .Ar identifier
461: .Cx
462: Print the full qualification of the given identifer, i.e.
463: the outer blocks that the identifier is associated with.
464: .Dp Cx Ic up
465: .Cx \&\ \&
466: .Op Ar count
467: .Cx
468: .Dp Cx Ic down
469: .Cx \&\ \&
470: .Op Ar count
471: .Cx
472: Move the current function, which is used for resolving names,
473: up or down the stack
474: .Ar count
475: levels.
476: The default
477: .Ar count
478: is 1.
479: .Dp Ic where
480: Print out a list of the active procedures and function.
481: .Dp Cx Ic whereis
482: .Cx \&\ \&
483: .Ar identifier
484: .Cx
485: Print the full qualification of all the symbols whose
486: name matches the given identifier.
487: The order in which the symbols are printed is not meaningful.
488: .Dp
489: .Ss Accessing Source Files
490: .Pp
491: .Di L
492: .Dp Cx Ar /regular expression
493: .Op /
494: .Cx
495: .Dp Cx Ar ?regular expression
496: .Op ?
497: .Cx
498: Search forward or backward in the current source file
499: for the given pattern.
500: .Dp Cx Ic edit
501: .Cx \&\ \&
502: .Op Ar filename
503: .Cx
504: .Dp Cx Ic edit
505: .Cx \&\ \&
506: .Ar procedure/function-name
507: .Cx
508: Invoke an editor on
509: .Ar filename
510: or the current source file if none
511: is specified.
512: If a
513: .Ar procedure
514: or
515: .Ar function
516: name is specified,
517: the editor is invoked on the file that contains it.
518: Which editor is invoked by default depends on the installation.
519: The default can be overridden by setting the environment variable
520: .Ev EDITOR
521: to the name of the desired editor.
522: .Dp Cx Ic file
523: .Cx \&\ \&
524: .Op Ar filename
525: .Cx
526: Change the current source file name to
527: .Ar filename .
528: If none is specified then the current source file name is printed.
529: .Dp Cx Ic func
530: .Cx \&\ \&
531: .Op Ar procedure/function
532: .Cx
533: Change the current function.
534: If none is specified then print the current function.
535: Changing the current function implicitly changes the current source file
536: to the one that contains the function; it also changes the current scope
537: used for name resolution.
538: .Dp Cx Ic list
539: .Cx \&\ \&
540: .Op Ar source-line-number Op Ic \&, Ar source-line-number
541: .Cx
542: .Dp Cx Ic list
543: .Cx \&\ \&
544: .Ar procedure/function
545: .Cx
546: List the lines in the current source file from the first line number to
547: the second inclusive.
548: If no lines are specified, the next 10 lines are listed.
549: If the name of a procedure or function is given
550: lines
551: .Ar n-k
552: to
553: .Ar n+k
554: are listed where
555: .Ar n
556: is the first statement
557: in the procedure or function and
558: .Ar k
559: is small.
560: .Dp Cx Ic use
561: .Cx \&\ \&
562: .Ar directory-list
563: .Cx
564: Set the list of directories to be searched
565: when looking for source files.
566: .Dp
567: .Ss Command Aliases and Variables
568: .Dw Fl
569: .Di L
570: .Dp Cx Ic alias
571: .Cx \&\ \&
572: .Ar name
573: .Cx \&\ \&
574: .Ar name
575: .Cx
576: .Dp Cx Ic alias
577: .Cx \&\ \&
578: .Ar name
579: .Cx \&\ \&
580: .Ar string
581: .Cx
582: .Dp Cx Ic alias
583: .Cx \&\ \&
584: .Ar name (parameters)
585: .Cx \&\ \&
586: .Cx ``
587: .Ar string
588: .Cx \'\'
589: .Cx
590: When commands are processed,
591: dbx first checks to see if the word
592: is an alias for either a command or a string.
593: If it is an alias, then dbx treats the input as though
594: the corresponding string (with values substituted for any parameters)
595: had been entered.
596: For example,
597: to define an alias ``rr'' for the command ``rerun'',
598: one can say
599: .Pp
600: .Dl alias rr rerun
601: .Pp
602: To define an alias called ``b'' that sets a stop at a particular line
603: one can say
604: .Pp
605: .Dl alias b(x) ``stop at x''
606: .Pp
607: Subsequently, the command ``b(12)'' will expand to ``stop at 12''.
608: .Pp
609: .Dp Cx Ic set
610: .Ws
611: .Ar name
612: .Op \&= Ar expression
613: .Cx
614: The
615: .Ic set
616: command defines values for debugger variables.
617: The names of these variables cannot conflict with names in the program
618: being debugged, and are expanded to the corresponding expression
619: within other commands.
620: The following variables have a special meaning:
621: .Dw Ds
622: .Di L
623: .Dp Li $frame
624: Setting this variable to an address causes dbx to use the stack frame
625: pointed to by the address for
626: doing stack traces and accessing local variables.
627: This facility is of particular use for kernel debugging.
628: .Dp Li $hexchars
629: .Dp Li $hexints
630: .Dp Li $hexoffsets
631: .Dp Li $hexstrings
632: When set, dbx prints out
633: out characters, integers, offsets from registers, or character pointers
634: respectively in hexadecimal.
635: .Dp Li $listwindow
636: The value of this variable specifies the number
637: of lines to list around a function or when the
638: .Ic list
639: command
640: is given without any parameters.
641: Its default value is 10.
642: .Dp Li $mapaddrs
643: Setting (unsetting) this variable causes dbx to start (stop)
644: mapping addresses.
645: As with ``$frame'', this is useful for kernel debugging.
646: .Dp Li $unsafecall
647: .Dp Li $unsafeassign
648: When ``$unsafecall'' is set,
649: strict type checking is turned off for arguments to
650: subroutine or function calls (
651: .Ar e .g .
652: in the
653: .Ic call
654: statement).
655: When ``$unsafeassign'' is set,
656: strict type checking between the two sides
657: of an
658: .Ic assign
659: statement is turned off.
660: These variables should be used only with great care,
661: because they severely limit dbx's usefulness
662: for detecting errors.
663: .Dp
664: .Dp Cx Ic unalias
665: .Cx \&\ \&
666: .Ar name
667: .Cx
668: Remove the alias with the given name.
669: .Dp Cx Ic unset
670: .Cx \&\ \&
671: .Ar name
672: .Cx
673: Delete the debugger variable associated with
674: .Ar name .
675: .Dp
676: .Ss Machine Level Commands
677: .Dw Fl
678: .Di L
679: .Dp Cx Ic tracei
680: .Cx \&\ \&
681: .Op Ar address
682: .Cx \&\ \&
683: .Op .Ic if Ar cond
684: .Cx
685: .Dp Cx Ic tracei
686: .Cx \&\ \&
687: .Op Ar variable
688: .Cx \&\ \&
689: .Op Ic at Ar address
690: .Cx \&\ \&
691: .Op Ic if Ar cond
692: .Cx
693: .Dp Cx Ic stopi
694: .Cx \&\ \&
695: .Op Ar address
696: .Cx \&\ \&
697: .Op Ic if Ar cond
698: .Cx
699: .Dp Cx Ic stopi
700: .Cx \&\ \&
701: .Op Ic at
702: .Cx \&\ \&
703: .Op Ar address
704: .Cx \&\ \&
705: .Op Ic if Ar cond
706: .Cx
707: Turn on tracing or set a stop using a machine instruction address.
708: .Dp Ic stepi
709: .Dp Ic nexti
710: Single step as in
711: .Ic step
712: or
713: .Ic next ,
714: but do a single instruction
715: rather than source line.
716: .Dp Cx Ar address
717: .Cx \&,
718: .Ar address
719: .Cx \&/
720: .Op Ar mode
721: .Cx
722: .Dp Cx Ar address
723: .Cx \&/
724: .Op Ar count
725: .Op Ar mode
726: .Cx
727: Print the contents of memory starting at the first
728: .Ar address
729: and continuing up to the second
730: .Ar address
731: or until
732: .Ar count
733: items are printed.
734: If the address is ``.'', the address following the one
735: printed most recently is used.
736: The
737: .Ar mode
738: specifies how memory is to be printed;
739: if it is omitted the previous mode specified is used.
740: The initial mode is ``X''.
741: The following modes are supported:
742: .Dw Cm
743: .Dp Cm i
744: print the machine instruction
745: .Dp Cm d
746: print a short word in decimal
747: .Dp Cm D
748: print a long word in decimal
749: .Dp Cm o
750: print a short word in octal
751: .Dp Cm O
752: print a long word in octal
753: .Dp Cm x
754: print a short word in hexadecimal
755: .Dp Cm X
756: print a long word in hexadecimal
757: .Dp Cm b
758: print a byte in octal
759: .Dp Cm c
760: print a byte as a character
761: .Dp Cm s
762: print a string of characters terminated by a null byte
763: .Dp Cm f
764: print a single precision real number
765: .Dp Cm g
766: print a double precision real number
767: .Dp
768: .Pp
769: Symbolic addresses are specified by preceding the name with an ``&''.
770: Registers are denoted by ``$rN'' where N is the number of the register.
771: Addresses may be expressions made up of other addresses and
772: the operators ``+'', ``-'', and indirection (unary ``*'').
773: .Dp
774: .Ss Miscellaneous Commands
775: .Tw Ic
776: .Tp Ic gripe
777: Invoke a mail program to send a message to the person in charge of
778: .Nm dbx .
779: .Tp Ic help
780: Print out a synopsis of
781: .Nm dbx
782: commands.
783: .Tp Ic quit
784: Exit
785: .Nm dbx .
786: .Tp Cx Ic sh
787: .Cx \&\ \&
788: .Ar command-line
789: .Cx
790: Pass the command line to the shell for execution.
791: The SHELL environment variable determines which shell is used.
792: .Tp Cx Ic source
793: .Cx \&\ \&
794: .Ar filename
795: .Cx
796: Read
797: .Nm dbx
798: commands from the given
799: .Ar filename .
800: .Tp
801: .Sh ENVIRONMENT
802: .Nm Dbx
803: utilizes the following environment variables:
804: .Ds I
805: EDITOR
806: HOME
807: PATH
808: SHELL
809: .De
810: .Sh FILES
811: .Dw .dbxinit
812: .Di L
813: .Dp Pa a.out
814: object file
815: .Dp Pa .dbxinit
816: initial commands
817: .Dp
818: .Sh SEE ALSO
819: .Xr cc 1 ,
820: .Xr mod l ,
821: .Xr f77 1 ,
822: .Xr pc 1
823: .Sh HISTORY
824: .Nm Dbx
825: appeared in 4.2 BSD.
826: .Sh BUGS
827: .Nm Dbx
828: suffers from the same ``multiple include'' malady as did
829: .Nm sdb .
830: If you have a program consisting of a number of object files
831: and each is built from source files that include header files,
832: the symbolic information for the header files is replicated in
833: each object file.
834: Since about one debugger start-up is done for each link,
835: having the linker
836: .Xr ld 1
837: re-organize the symbol information
838: would not save much time, though it would reduce some of the
839: disk space used.
840: .Pp
841: This problem is an artifact of the unrestricted semantics
842: of #include's in C; for example an include file can contain
843: static declarations that are separate entities for each file
844: in which they are included.
845: However, even with Modula-2 there is a substantial amount of duplication
846: of symbol information necessary for inter-module type checking.
847: .Pp
848: Some problems remain with the support for individual languages.
849: Fortran problems include:
850: inability to assign to logical, logical*2, complex
851: and double complex variables;
852: inability to represent parameter constants
853: which are not type integer or real;
854: peculiar representation for the values of dummy procedures
855: (the value shown for a dummy procedure is actually
856: the first few bytes of the procedure text;
857: to find the location of the procedure,
858: use ``&'' to take the address of the variable).
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