17 Oct
2014
17 Oct
'14
1:51 a.m.
Hi folks,
I've been looking at Unix v5 cc limitations.
It seems like early cc could only use variable and function names up
to 8 characters.
This limitation occurs in v5, v6 and v7.
But when using the nm utility to print out the name list I see
function test1234() listed as:
000044T _test123
That seems to suggest that only the first 7 characters are
significant, but when looking at other sources they stated that one
can use up to 8 characters.
I hacked up a short program to test this:
main()
{
test1234();
test1235();
}
test1234()
{
printf ("\nWorking");
}
test1235()
{
printf ("\nAlso working");
}
This generated:
Multiply defined: test5.o;_test123
So it would seem that function names can only be 7 characters in
length. I am not sure if limitations of early cc were documented
anywhere. When I backported unirubik to v5 it compiled the longer
functions without any problem.
Did anyone document these sorts of limitations of early cc? Does
anyone remember when cc started to use function names longer than 7
characters?
Mark
17 Oct
17 Oct
2:20 a.m.
External names were limited to 7 (user-defined) characters because the compiler prepended
the _ to them. Function names were always external in that era of C. Internal variables
could be up to 8 characters. As for longer names, they were allowed but only the first 8 (
including the compiler supplied _ for external names) were signiicant.
I'll look for my documentation from v6.
- Milo
On Oct 16, 2014, at 8:51 PM, Mark Longridge wrote:
Hi folks,
I've been looking at Unix v5 cc limitations.
It seems like early cc could only use variable and function names up
to 8 characters.
This limitation occurs in v5, v6 and v7.
But when using the nm utility to print out the name list I see
function test1234() listed as:
000044T _test123
That seems to suggest that only the first 7 characters are
significant, but when looking at other sources they stated that one
can use up to 8 characters.
I hacked up a short program to test this:
main()
{
test1234();
test1235();
}
test1234()
{
printf ("\nWorking");
}
test1235()
{
printf ("\nAlso working");
}
This generated:
Multiply defined: test5.o;_test123
So it would seem that function names can only be 7 characters in
length. I am not sure if limitations of early cc were documented
anywhere. When I backported unirubik to v5 it compiled the longer
functions without any problem.
Did anyone document these sorts of limitations of early cc? Does
anyone remember when cc started to use function names longer than 7
characters?
Mark
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https://minnie.tuhs.org/mailman/listinfo/tuhs
2:21 a.m.
On Thu, 16 Oct 2014, Mark Longridge wrote:
It seems like early cc could only use variable and
function names up to
8 characters.
In those days it took only the first seven and ignored the rest,
prepending an underscore as you discovered. I don't remember when longer
names were recognised; for all I know it could've been around when
pathnames could be longer than 14 chars (which I think may have been a
BSDism).
--
Dave Horsfall (VK2KFU)
http://www.horsfall.org/spam.html
1:35 p.m.
On Thu, Oct 16, 2014, at 22:21, Dave Horsfall wrote:
On Thu, 16 Oct 2014, Mark Longridge wrote:
For externals, it's a limitation of the PDP-11 a.out format. Other
systems may or may not have had the same limit or a different limit.
For VAX, 4BSD appears to use an "index into file string table", whereas
3BSD still has an 8-character string. I don't see any provision in the
4BSD linker for loading 3BSD binaries.
Filenames over 14 characters appear to have been introduced in 4.1BSD.
It seems like early cc could only use variable
and function names up to
8 characters.
In those days it took only the first seven and ignored the rest,
prepending an underscore as you discovered. I don't remember when longer
names were recognised; for all I know it could've been around when
pathnames could be longer than 14 chars (which I think may have been a
BSDism). 
1:44 p.m.
On Oct 17, 2014, at 7:35 AM, random832(a)fastmail.us wrote:
On Thu, Oct 16, 2014, at 22:21, Dave Horsfall wrote:
As someone that wrote an assembler and a linker/loader for the VAX
back in the day (for my first CS class), I know that 4.2 definitely had
the string table, as did all the descendants that I encountered in the
field back during the great unix wars when I was instructed by my employer
to obfuscate certain symbols to “protect” IP.
Warner
On Thu, 16 Oct 2014, Mark Longridge wrote:
For externals, it's a limitation of the PDP-11 a.out format. Other
systems may or may not have had the same limit or a different limit.
For VAX, 4BSD appears to use an "index into file string table", whereas
3BSD still has an 8-character string. I don't see any provision in the
4BSD linker for loading 3BSD binaries. It seems like early cc could only use variable
and function names up to
8 characters.
In those days it took only the first seven and ignored the rest,
prepending an underscore as you discovered. I don't remember when longer
names were recognised; for all I know it could've been around when
pathnames could be longer than 14 chars (which I think may have been a
BSDism). Filenames over 14 characters appear to have been
introduced in 4.1BSD.
_______________________________________________
TUHS mailing list
TUHS(a)minnie.tuhs.org
https://minnie.tuhs.org/mailman/listinfo/tuhs
2:07 p.m.
Warner Losh <imp(a)bsdimp.com> wrote:
> For VAX, 4BSD appears to use an "index into
file string table", whereas
> 3BSD still has an 8-character string. I don't see any provision in the
> 4BSD linker for loading 3BSD binaries.
I think System III or System V picked this up.
> Filenames over 14 characters appear to have been
introduced in 4.1BSD.
No, at 4.2 BSD with the Fast Filesystem. (Maybe 4.1c or some such
already had the FFS, but the original 4.1 didn't...)
Arnold
2:22 p.m.
On Oct 17, 2014, at 9:07 AM, arnold(a)skeeve.com wrote:
Warner Losh <imp(a)bsdimp.com> wrote:
Right!
McKusick, et al. say that it came with the Fast Filesystem in 4.2 [1]
I recall a presentation at UW in Madison where he said, (paraphrasing from memory) We
heard you guys. We included long file names in the Fast File System. (loud cheers)
- Milo
[1] https://www.cs.berkeley.edu/~brewer/cs262/FFS.pdf
> For VAX, 4BSD appears to use an "index
into file string table", whereas
> 3BSD still has an 8-character string. I don't see any provision in the
> 4BSD linker for loading 3BSD binaries.
I think System III or System V picked this up.
> Filenames over 14 characters appear to have
been introduced in 4.1BSD.
No, at 4.2 BSD with the Fast Filesystem. (Maybe 4.1c or some such
already had the FFS, but the original 4.1 didn't...)
Arnold
7:29 p.m.
On Fri, Oct 17, 2014, at 10:07, arnold(a)skeeve.com wrote:
I was looking at 4.1c in the archive, sorry for not being clear.
Warner Losh <imp(a)bsdimp.com> wrote:
What's actually quoted is what I wrote.
> For VAX,
4BSD appears to use an "index into file string table", whereas
> 3BSD still has an 8-character string. I don't see any provision in the
> 4BSD linker for loading 3BSD binaries.
I think System III or System V picked this up.
> Filenames over 14 characters appear to have
been introduced in 4.1BSD.
No, at 4.2 BSD with the Fast Filesystem. (Maybe 4.1c or some such
already had the FFS, but the original 4.1 didn't...) 
18 Oct
18 Oct
7:25 a.m.
On Thursday, 16 October 2014 at 21:51:56 -0400, Mark Longridge wrote:
So it would seem that function names can only be 7
characters in
length. I am not sure if limitations of early cc were documented
anywhere.
This is really an identifier issues, and it's documented in K&R 1st
edition, page 179:
DEC PDP-11 7 characters, 2 cases
Honeywell 6000 6 characters, 1 case
IBM 360/370 7 characters, 1 case
Interdata 8/32 8 characters, 2 cases
Greg
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3478
days inactive
3479
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8 comments
8 participants
participants (8)
-
arnold＠skeeve.com -
Dave Horsfall -
Greg 'groggy' Lehey -
Mark Longridge -
Milo Velimirovic -
Milo Velimirović
-
random832＠fastmail.us -
Warner Losh