rgenter@labs-b.bbn.com (Rick Genter) (09/16/86)
Yes, it will work to interchange (int) and (char) as the types of
function arguments, as long as you *never* use &, or *only* work on VAXen
(and similar-endian machines). At my previous employer we had a late-night
hacker who had written a really nice screen editor. One day I tried to port
it to the Sun. Nothing worked (core dumped before clearing the screen). I
started to track it down, then noticed things like:
<...>
add_char_to_line (':'); /* draw border */
<...>
add_char_to_line (c)
{ /* no decl for c, so default to int */
<...>
ins_char_in_buffer (& c, & buf);
}
ins_char_in_buffer (cp, bufp)
char *cp;
BUF *bufp;
{
<...>
}
Needless to say, this kind of coding was sprinkled throughout the source.
Dennis would have liked this guy; I said "lint" to him and he replied "?" :-).
The moral of the story: say what you mean, even if it *usually* doesn't
matter.
--------
Rick Genter BBN Laboratories Inc.
(617) 497-3848 10 Moulton St. 6/512
rgenter@labs-b.bbn.COM (Internet new) Cambridge, MA 02238
rgenter@bbn-labs-b.ARPA (Internet old) linus!rgenter%BBN-LABS-B.ARPA (UUCP)chris@mimsy.umd.edu (Chris Torek) (09/16/86)
From: Rick Genter <rgenter@labs-b.bbn.com>
Yes, it will work to interchange (int) and (char) as the
types of function arguments, as long as you *never* use &,
or *only* work on VAXen (and similar-endian machines).
It will work at other times as well.
I tried to port [code like the below] to the Sun.
add_char_to_line (':'); /* draw border */
add_char_to_line (c)
{ /* no decl for c, so default to int */
<...>
ins_char_in_buffer (& c, & buf);
}
ins_char_in_buffer (cp, bufp)
char *cp;
BUF *bufp;
{
<...>
}
This code is wrong, and lint will say so. It is wrong not because
':' is an int, and add_char_to_line's parameter is therefore int,
but because add_char_to_line's parameter is declared as an int and
its address (type `int *') is passed to a function expecting type
`char *'. Were add_char_to_line declared as
add_char_to_line(c)
char c;
{
...
ins_char_in_buffer(&c, &buf);
}
the code would have been correct (even though the call to
add_char_to_line above passes ':', which has type `int': this is
another place where automatic promotion has odd effects).
Dennis would have liked this guy; I said "lint" to him and
he replied "?" :-).
Actually, I believe `?' is due to Kernighan. (Anyone at You Know
Where care to comment?)
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP: seismo!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu