[TUHS] nm on Third Edition .o files?'

[Clem Cole]

touchė

On Tue, Dec 20, 2016 at 3:23 PM, Steve Johnson <scj at yaccman.com> wrote:

> I had a funny and somewhat embarrassing experience around the whole issue
> of structure name spaces.  When types were spreading through C, we had a
> lot of discussion about whether we should require all programs to call
> structures with a structure pointer (which would allow a separate name
> space for structure members of each structure).   We all thought it was a
> good idea, but the problem was there was a lot of code out there that
> didn't conform, including a lot of OS code.  As we started to port Unix to
> the Interdata (a 32-bit machine), the situation became critical.  So I took
> a deep breath and implemented the following: the compiler would use the old
> style structure rules until I saw a "new style" structure reference in the
> code.  At that point I would start to enforce the new rules, which involved
> translating the symbol table, and starting to complain if the types didn't
> match.   This was a very ugly hack, and I had inserted many firewalls and
> assertions to check that the data structures were correct after this
> translation.
>
> Now, a word about error messages.  The PDP-11 didn't have much memory.
> But at the same time it didn't have much of a debugger in those days.  So
> the main aim was to identify what went wrong in a small number of
> characters so you could put in print statements and run it again.  This
> meant that the message produced had to be short but also unique.  I was
> producing error checks at a great rate in this code and running out of
> synonyms for "corrupted" in my messages.
>
> I "published" the code, and everything seemed to be working for a couple
> of days.  Then Ken, who was working on the Interdata file system, tried to
> compile a structure declaration that contained a sizeof of a structure that
> was recursively declared inside of the sizeof, and my code gave up the
> ghost.  Ken came into my office with a strange look on his face and asked
> "What is a gummy structure?"
>
>
> ----- Original Message -----
> From:
> "Clem Cole" <clemc at ccc.com>
>
> To:
> "Larry McVoy" <lm at mcvoy.com>
> Cc:
> "TUHS main list" <tuhs at minnie.tuhs.org>, "Noel Chiappa" <
> jnc at mercury.lcs.mit.edu>
> Sent:
> Tue, 20 Dec 2016 11:21:41 -0500
> Subject:
> Re: [TUHS] nm on Third Edition .o files?'
>
>
>
> On Tue, Dec 20, 2016 at 11:09 AM, Larry McVoy <lm at mcvoy.com> wrote:
>
>> I get that it doesn't scale but man, so nice when reading
>> code to know that s.st_size is a stat structure.
>>
>
> ​Amen!!!​
>
>
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