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* [TUHS] SDB debugger
@ 2020-05-01 20:48 Paul Ruizendaal
  2020-05-01 21:57 ` Clem Cole
                   ` (3 more replies)
  0 siblings, 4 replies; 26+ messages in thread
From: Paul Ruizendaal @ 2020-05-01 20:48 UTC (permalink / raw)
  To: TUHS main list

Reading some more stuff about the road from 7th Edition to 8th Edition, this time about debuggers.

My current understanding is as follows:

- On 6th edition the debugger was ‘cdb’

- On 7th edition it was ‘adb’, a rewrite / evolution from ‘cdb’

- In 32V a new debugger appears, ‘sdb’. Its code seems a derivative from ‘adb’, but the command language is substantially reworked and it uses a modified variant of the a.out linker format - in essence the beginnings of ‘stabs’. Of course the compiler, assembler, linker and related tools all emit/recognize these new symbol table elements. 

- The July 78 file note by London/Reiser does not mention a reworked debugger at all; the 32V tape that is on TUHS has ’sdb' files that are dated Feb/Mar 1979. This stuff must have been developed between July 78 and March 79.

- In the SysIII and 3BSD code on TUHS (from early 80 and late 79 respectively) the stabs format is more developed. For SysIII it is ‘VAX only’. With these roots, it is not surprising that it is also in 8th Edition.


Two questions:

(1) According to Wikipedia the original author of the stabs format is unknown. It also says that the original author of ‘sdb’ is unknown. Is that correct, is the author really unknown?

(2) As far as I can tell, the ’sdb’ debugger was never back ported to 16 bit Unix, not in the SysIII line and not in the 2.xBSD line. It would seem to me that the simple stabs format of 32V would have lent itself to being back ported. Is it correct that no PDP11 Unix used (a simple) stabs tool chain and debugger?




^ permalink raw reply	[flat|nested] 26+ messages in thread
* Re: [TUHS] DEC Compilers (was: Re: SDB debugger
@ 2020-05-06  2:52 Doug McIlroy
  0 siblings, 0 replies; 26+ messages in thread
From: Doug McIlroy @ 2020-05-06  2:52 UTC (permalink / raw)
  To: tuhs

> random small C programs with computable expected outputs

"computable" is subtle here. The only way to compute the
outputs was to run the program. McKeeman's trick was to
sic several completely unrelated compilers on the program
and let them vote on the answer.

Compile time was measured. My favorite "bug" was the
mmany minutes it took to compile a constant expression
that involved shifting a constant INT_MAX bits by
performing that many 1-bit shifts.

Doug

^ permalink raw reply	[flat|nested] 26+ messages in thread
* Re: [TUHS] DEC Compilers (was: Re: SDB debugger
@ 2020-05-06 15:53 Doug McIlroy
  2020-05-06 20:21 ` Tim Rylance
  0 siblings, 1 reply; 26+ messages in thread
From: Doug McIlroy @ 2020-05-06 15:53 UTC (permalink / raw)
  To: tuhs

>> Compile time was measured. My favorite "bug" was the
>> many minutes it took to compile a constant expression
>> that involved shifting a constant INT_MAX bits by
>> performing that many 1-bit shifts.
>
> I don't know if this anecdote is an urban legend or if it really
> happened.  I was told [a similar] story when I was interning as an operator
> at my alma mater, which was an IBM System/360 shop.

I heard it not from the grapevine, but from McKeeman himself.

Doug

^ permalink raw reply	[flat|nested] 26+ messages in thread

end of thread, other threads:[~2020-05-12  4:16 UTC | newest]

Thread overview: 26+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-01 20:48 [TUHS] SDB debugger Paul Ruizendaal
2020-05-01 21:57 ` Clem Cole
2020-05-02  9:10   ` Paul Ruizendaal
2020-05-02 16:04     ` Clem Cole
2020-05-01 23:05 ` Jeremy C. Reed
2020-05-02  0:49 ` Noel Hunt
2020-05-02  1:22   ` Rob Pike
2020-05-02  3:49     ` Noel Hunt
2020-05-02 20:16   ` Paul Ruizendaal
2020-05-03  6:58     ` arnold
2020-05-03 16:13     ` Clem Cole
2020-05-03 16:53       ` Henry Bent
2020-05-03 17:06         ` Henry Bent
2020-05-03 17:13       ` Henry Bent
2020-05-03 20:26         ` Clem Cole
2020-05-05  0:22           ` [TUHS] DEC Compilers (was: " Win Treese
2020-05-05 17:36             ` Paul Winalski
2020-05-05 18:53               ` Dr Iain Maoileoin
2020-05-05 21:59               ` Dan Cross
2020-05-05 21:49             ` Henry Bent
2020-05-03 17:35       ` [TUHS] " Paul Winalski
2020-05-03 21:27       ` Paul Ruizendaal
2020-05-12  4:15 ` Dave Horsfall
2020-05-06  2:52 [TUHS] DEC Compilers (was: " Doug McIlroy
2020-05-06 15:53 Doug McIlroy
2020-05-06 20:21 ` Tim Rylance

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