unsigned what?

Guy Harris guy at rlgvax.UUCP
Fri Jun 22 15:31:07 AEST 1984

"unsigned short x;" and "unsigned long x;" aren't Berkeleyisms.  The 4.1BSD
C compiler differs from the System III C compiler ("compiler" here refers
to "/lib/ccom") in 1) the addition of "flexnames", 2) a mod not to put anything
shorter than 32 bits declared "register" into a register, and 3) other
very minor changes - these differences were found by using the "diff" command.

The System V source file "getty.c" contains the line

	unsigned short timer;

so the System V compiler supports it (any other result would have surprised
the living **** out of me).  Therefore:

	1) the PDP-11 V7 Ritchie compiler already supported them, and your
	   compiler (being based on that compiler) didn't need to be changed
	   to support them.

	2) your System V source to "getty.c" (and some other programs,
	   probably) was a PDP-11 distribution; the PDP-11 S5 compiler
	   doesn't support "unsigned short x;"; and all file using this
	   construct were modified not to use it.

	3) somebody at BB&N changed "getty.c".

I infer from what you say that 3) isn't the case.  2) is unlikely, but not
impossible; I put my money on 1).

I interpret "8.2 Type specifiers" to say that there are two classes of
"type-specifier", adjectives and nouns.  "long", "short", and "unsigned"
are adjectives, and the others are nouns.  ("The words 'long', 'short', and
'unsigned' may be thought of as adjectives...")  A declaration consists of one
noun ("Otherwise, at most one type-specifier may be given in a declaration.")
and several adjectives.  The adjectives "short", "long", and "unsigned"
may modify "int", and the adjective "long" may modify "float".  No other
combinations of adjective and noun are permitted.  ("...the following
combinations are acceptable.")

In the statement "If the type-specifier is missing from a declaration, it
is taken to be 'int'.", I interpret "the type-specifier" to refer back to
the "one type-specifier given in a declaration" mentioned in the previous
sentence.  As such, in "unsigned short int" the "int" is the missing
type-specifier, so "unsigned short" is a declaration with the type-specifier
(in the sense used in that sentence) missing and taken as "int".

I see no reason this shouldn't be considered a legitimate interpretation; I
don't find it far-fetched, forbidding "unsigned" to be applied to "short int"
and "long int" reduces the usefulness of the language, *and* it describes
current practice for a lot of existing compilers and code.  I consider the
other interpretations legitimate as well, which is why I consider the passage

	Guy Harris

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