Path: utzoo!mnetor!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!ames!pacbell!att-ih!att-cb!clyde!watmath!watdragon!violet!gjditchfield
From: gjditchfield@violet.waterloo.edu (Glen Ditchfield)
Newsgroups: comp.lang.c++
Subject: possible bugs
Message-ID: <6112@watdragon.waterloo.edu>
Date: 30 Mar 88 21:58:38 GMT
Sender: daemon@watdragon.waterloo.edu
Distribution: na
Lines: 74
Keywords: typedef, stream.h, pointer-to-function parameters


Here's three possible bugs in C++, using cfront 1.2.1 and BSD4.3 on
a Vax.  (The CC command has been renamed ccc locally.)

1) Cfront silently absorbs typedefs inside classes, to the confusion of C.
	----------------------------------------
	class bar {
	  public:
	    typedef int* ip;
	    ip i;
	    };
	----------------------------------------
	ccc  typedef.cc:
	cc  -c  typedef..c
	"typedef.cc", line 4: syntax error
	"typedef.cc", line 4: warning: Missing ',' or '=' in variable
		declaration
	"typedef.cc", line 4: warning: undeclared initializer name _bar_i
	"typedef.cc", line 4: illegal initialization
	"typedef.cc", line 5: syntax error
	----------------------------------------
   I have no idea how typedef should interact with public/private/protected,
   but cc should not produce error messages.

2) Declaration of "complex" variables in the middle of code causes
   confusion about the scope of other variables.
	----------------------------------------
	#include <stream.h>
	void foo() {
	    for (int i = 1; i <= 10; i += 1) {
		}
	    filebuf fb;
	    for (char *i = (char *)0; i != 0; i += 1) {
		}
	    }
	----------------------------------------
   If "filebuf fb;" is commented out, the messages produced are
	ccc  redef2.cc:
	"redef2.cc", line 6: error: two declarations of i
   Similar messages are produced if the filebuf declaration is replaced by
   a declaration of an integer and the #include is removed.

   If "filebuf fb;" is not commented out, the messages produced are
	ccc  redef2.cc:
	cc  -c  redef2..c
	"redef2.cc", line 6: warning: "_au1_i" redefinition hides earlier one
   Again, a C error is produced.

3) This is more likely to be my misunderstanding than a bug.  The syntax in
   the back of "The C++ Programming Language" suggests that functions can
   have pointer-to-function parameters, but I get (uninformative) error
   messages unless I use a typedef.
	----------------------------------------
	typedef int (*PFCCI)(char, char); // ptr to fn mapping 2 chars to int.
	
	void f( PFCCI p);
	
	void g( int (*p)(char, char) );
	----------------------------------------
	ccc  pmf.cc:
	"pmf.c", line 5: error: syntax error
	"pmf.cc", line 5: error: syntax error
	"pmf.cc", line 5: error: syntax error
	----------------------------------------
   Does C++ require the typedef, or have I just messed up the declaration
   of g?

4) Is there a better place to send complaints to than this group?  The
   local C++ maintainer doesn't know of one.

Glen Ditchfield                              watmath!violet!gjditchfield
Dept of Computer Science, U of Waterloo         (519) 885-1211 x6658
Waterloo, Ontario, Canada			   Office: MC 2006
	  I'm the compiler user your professors warned you about.