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From: geoff@cs.warwick.ac.uk (Geoff Rimmer)
Newsgroups: comp.lang.c,comp.std.c
Subject: Some Comments & Questions about ANSI C
Message-ID: <GEOFF.89Jun11231924@onyx.cs.warwick.ac.uk>
Date: 11 Jun 89 22:19:24 GMT
Sender: news@warwick.ac.uk
Followup-To: comp.lang.c
Organization: Computer Science, Warwick University, UK
Lines: 76


1. 15 standard include files are listed in K&R2.  Only 12 are
described in sufficient detail.  The other three are

	errno.h	 - this will contain the #defines for error messages.
		   But will it contain the declaration "extern int errno" ?
	locale.h - This will contain "properties that depend on local
		   language, nationality, or culture".  Such as?
	stddef.h - Definition of the type size_t (A7.4.8).  But what
		   else goes in here?  ino_t and dev_t presumably stay
		   in sys/types.h (8.6 p 181).

2. It seems to me that every time I want to #include <stdio.h>, I must
also #include <stdarg.h> and <stddef.h> beforehand.  This is to stop
it barfing on the function declarations in <stdio.h> like

	size_t fread( void *, size_t, size_t, FILE * );
		/* size_t is defined in <stddef.h> */

and
	int vprintf( const char *, va_list );
		/* va_list is defined in <stdarg.h> */

I find this annoying sometimes, especially when working on a simple
program that is only including <stdio.h> to get _iobuf defined.  Am I
correct on this?

3. Am I missing something, or is "difftime" the most simple function
around?  It seems to me that it is essentially a subtract:

	double difftime( time_t t2, time_t t1)
	{
		return (double)t2 - t1;
	}
In which case, why is it a function?  I'd rather do a subtraction myself!

4. I'm still not entirely sure I understand "void *".  If I have a
function which takes as argument a void *, and I want to pass it the
variable x (which could be of type char *, int *, or even
float(*)(int,char*) ), do I have to CAST x to a (void *) when calling
the function?  Similarly, if the function then returned a void *, and
I have a variable y of type int *, would I have to do
	y = (int *) function (......);
?

5. Does the standard say anything about where function definitions for
fopen and opendir must go?  Also, is <dirent.h> mentioned in the
standard, or is it up to the individual implementor to choose this?

6. Finally, I see there's no strdup in ANSI C.  Sigh.  I guess it's
back to 

	#define strdup(x) (strcpy(Malloc(strlen(x)+1),(x)))

	:-(

Geoff
	One of these days, I'm going to write an ANSI C compiler.  And
	whenever it encounters some code whose behavior is undefined
	(such as fflush(stdin);) it will draw a picture of Snow White (tm) 
	on the screen, and then play Rule Brittania 3 times, before
	crashing with a segmentation fault, and leaving a
		while(1){fork();malloc(UINT_MAX);}
	running in the background. 

	/---------------------------------------------------------------\
	|	GEOFF RIMMER						|
	|	email	: geoff@uk.ac.warwick.cs			|
	|	address : Computer Science Dept, Warwick University, 	|
	|		  Coventry, England.				|
	|	PHONE	: +44 203 692320				|
	|	FAX	: +44 865 726753				|
	\---------------------------------------------------------------/

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