signed/unsigned char/short/int/long [was: #defines with parameters]

[Piercarlo Grandi]

First of all I wish to admit I have been inaccurate; as somebody remarked
"noalias" was only briefly in the dpANS C, and "far" and "near" never
actually made it in the official documents sent out for review. But all
were for a long time in various drafts, and as usually happens people
actually advertised "far" and "near" as examples of draft, unofficial
ANSI C conformance. Thank goodness X3J11 frustrated their efforts in the end.

In article <225 at twwells.uucp> bill at twwells.UUCP (T. William Wells) writes:

    In article <277 at aber-cs.UUCP> pcg at cs.aber.ac.uk (Piercarlo Grandi) writes:
    : As I understand it, this means that char,short,int,long are distinct
    : types, whereas unsigned and signed are type modifiers. In a sense then,
    : the view of dpANS is that unsigned [int] and [signed] int are the same
    : type, only that one has a sign and the other hasn't.
    
    If you want to, you can think of this as types and modifiers, though
    the standard does not speak of them that way. If so, here is how you
    do it:
    
    The types:
    
    	char
    	int
    
    That's right. Only two.
    
    The modifiers:
    
    	unsigned        signed
    	short           long
    
    The first pair modifies char or int; the second int only. You can
    specify only one of each pair.

OK, the standard does not speak of modifiers and types, but then the
result is the long lists you give and lots of confusion. I think there
are two issues here, one the introduction of signed as a keyword, and
the other neat ways of defining semantics. As to the latter, the whole
type system would be greatly simplified if one were to say that

[1] there are two distinct types, int and unsigned; they are distinct
types because different rules of arithmetic apply to them. This would
make it clear, and I have found very few people that actually
understand that unsigned is not just "positive int", that the same
operators applied to int and unsigned have very different semantics.

[2] Each of the two distinct types may come in three different extra
lengths, char, short and long, that are exactly equivalent among them
for the same type except for the different size.

As to the last point, char has been so far just a short short; a char
value can be operated upon exactly as an integer. Historically char
constants have been really the size of integer constants...

I would have liked, instead of the unnecessary and confusing signed
modifier, a nice range(abs_max) modifier for types integer and
unsigned, and char/short/long defined in terms of it. This would have
added tremendously to the portability of programs. The lack of some
sort of ranges and the use of short and long are one of the few things
I dislike in Algol68 and C.

I hope such an interesting extension makes it into C++, or at least into
the GNU C++ compilers (hint hint Michael Tiemann!).

    There is no relationship between char and signed or unsigned char,
    other than that they occupy the same amount of storage.

Now I reiterate the question: why was a new keyword introduced "signed"
when it just sufficed to sanction the existing practice of some
compilers (PCC had it, more recent BSD versions fixed this "bug") to
say "int char" or better "char int"?

Since storage classes, modifiers, and type names could be given in any
order in a declaration; most compilers therefore simply collected
keywords, and set a flag in the symbol table entry for the variable for
each keyword they collected.

This meant that "int static char int static" was accepted as a legal
declaration by many compilers :-). This has been later often
"corrected", notably in 4BSD pcc. Amusingly it persists even today in
other compilers, among them g++ 1.27, where interestingly "sizeof (char
int)" is 4 and "sizeof (int char)" is 1 on a 68020... Of course in my
opinion both ought to be 1, or an order storageclass/modifier/type
might be enforced, making "int char" illegal and "sizeof (char int)"
equal to 1.
-- 
Piercarlo "Peter" Grandi			INET: pcg at cs.aber.ac.uk
Sw.Eng. Group, Dept. of Computer Science	UUCP: ...!mcvax!ukc!aber-cs!pcg
UCW, Penglais, Aberystwyth, WALES SY23 3BZ (UK)