tim@mtxinu.UUCP (Tim Wood) (03/19/88)
Subject: BSD C compiler bug?
Newsgroups: comp.unix,comp.lang.c
Keywords: comma notation
There seems to be a bug with comma notation in BSD C. (It shows up
on the Ultrix, MORE/BSD and Sun compilers, FYI).
This program:
1 # define NULL 0
2 main()
3 {
4 unsigned char **foo;
5 int fn();
6
7 foo = NULL;
8 foo = (NULL, NULL);
9 foo = ( !foo ? NULL : (fn(2), NULL) );
10 }
11
12 fn(a)
13 int a;
14 { return (a); }
15
gets 'cc' errors:
"comma.c", line 8: warning: illegal combination of pointer and integer, op =
"comma.c", line 9: warning: illegal combination of pointer and integer, op =
Removing the parentheses from line 8 results in:
"comma.c", line 9: warning: illegal combination of pointer and integer, op =
Leaving line 8 alone and replacing line 9 with:
foo = ( !foo ? NULL : fn(2), NULL );
or
foo = !foo ? NULL : fn(2), NULL;
gives the same errors (for lines 8 and 9).
K&R say that the result type & value of a comma expression are that of the
second term, which is NULL (0) in all cases here. And NULL is assignment
compatible to all pointers.
Or am I missing something?
-TW
{ihnp4!pacbell,pyramid,{uunet,ucbvax}!mtxinu}!sybase!tim
--
{ihnp4!pacbell,pyramid,{uunet,ucbvax}!mtxinu}!sybase!tim