duerksen@bsu-cs.bsu.edu (Joel L. Duerksen) (10/17/90)
The program below crashes on my computer.... Most compilers would
complain about the 0.0 and would require explicit type casting.
Orca/C compiles it just fine. The value of the double doesn't seem
to matter, except sometimes the integer will get weird values instead
of crashing the program.
ps. I don't normally subtract zero from numbers :-) I found this
while trying to port a piece of generic C code.
------------------
#include <stdio.h>
#include <stdlib.h>
void main(void)
{
int i;
i= 50;
i -= 0.0;
printf("i=%d\n", i);
}
Joel Duerksen
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ARPA: duerksen@bsu-cs.bsu.edutoddpw@tybalt.caltech.edu (Todd P. Whitesel) (10/18/90)
Well, I just tried it, and yes, it's a bug. Hopefully someone will have caught this and fixed it in the 1.1 update, if not then we ought to get in touch with byteworks and let them know that the type casting code has a bug in it. Todd Whitesel toddpw @ tybalt.caltech.edu
gwyn@smoke.BRL.MIL (Doug Gwyn) (10/18/90)
In article <11906@bsu-cs.bsu.edu> duerksen@bsu-cs.bsu.edu (Joel L. Duerksen) writes: >The program below crashes on my computer.... Most compilers would >complain about the 0.0 and would require explicit type casting. No, they would not. The C language requires that compilers happily accept the construct "i -= 0.0", which means "convert i to double, subtract 0.0, convert back to int, and store into i". I have no doubt that some compilers get this wrong, but if so it is a bug in the compiler.
toddpw@tybalt.caltech.edu (Todd P. Whitesel) (10/18/90)
jb10320@uxa.cso.uiuc.edu (Desdinova) writes: > Orca DOES require a typecast. But it doesn't complain. One of the >biggest problems with ORCA is it's lack of error messages, or inappropriate >error messages. It's makes programming difficult sometimes. Funny... I've found the error messages to be a fairly good safety net. The only three things I'd run into before this were the structure auto- initialization bug, a problem with using fread and fwrite (i.e. they trash memory in subtle ways), and an inability to declare a pointer to void as a normal variable or element of a structure (ANSI K&R is a little vague on whether you can actually do that -- anybody know?). Todd Whitesel toddpw @ tybalt.caltech.edu
gwyn@smoke.BRL.MIL (Doug Gwyn) (10/19/90)
In article <1990Oct18.023155.17388@nntp-server.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: >... an inability to declare a pointer to void as a >normal variable or element of a structure (ANSI K&R is a little vague on >whether you can actually do that -- anybody know?). If you mean, is struct { void *p; }; permitted in a strictly conforming program, then the answer is, of course it is. It doesn't have to be specifically mentioned in K&R 2nd Edition because it follows naturally from the rules.
toddpw@tybalt.caltech.edu (Todd P. Whitesel) (10/19/90)
jh4o+@andrew.cmu.edu (Jeffrey T. Hutzelman) writes: >1.) Never declare main as void. Main returns an int. Um, I have been writing void main (...) without problems ever since I got ORCA (over 1 month of extensive use). If I declare main as void then everything works; if I try to return something from main I get an error because main is declared to return void. In actuality, 1 thru 4 byte values are returned in registers, so it doesn't really matter as far as code generation is concerned unless you are returning a struct or a float. BTW- I am still using a beta. Todd Whitesel toddpw @ tybalt.caltech.edu
gwyn@smoke.BRL.MIL (Doug Gwyn) (10/20/90)
In article <1990Oct19.133843.26089@nntp-server.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: >jh4o+@andrew.cmu.edu (Jeffrey T. Hutzelman) writes: >>1.) Never declare main as void. Main returns an int. >Um, I have been writing void main (...) without problems ever since I >got ORCA (over 1 month of extensive use). If I declare main as void then >everything works; if I try to return something from main I get an error >because main is declared to return void. Jeffrey is correct. Since main() is expected to return an integer, it had better do so. Otherwise the C runtime startup code could get tangled up when it tries to use the (nonexistent) value. It may be that a particular version of a particular compiler does not create code that runs entirely amok when your program attempts this sort of abuse, but you shouldn't rely on that. Do it right and avoid potential problems.
toddpw@tybalt.caltech.edu (Todd P. Whitesel) (10/20/90)
ORCA/C manual, ch. 13 "C Programs", p. 205: "You may declare the function main as either a function returning an integer or as a function returning void." Sorry to nitpick. Todd Whitesel toddpw @ tybalt.caltech.edu
gwyn@smoke.BRL.MIL (Doug Gwyn) (10/21/90)
In article <1990Oct19.232345.5653@nntp-server.caltech.edu> toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: >"You may declare the function main as either a function returning an integer or >as a function returning void." But do it right anyway. You might someday want to compile your code using a compiler where it matters.
jh4o+@andrew.cmu.edu (Jeffrey T. Hutzelman) (10/25/90)
toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes: >ORCA/C manual, ch. 13 "C Programs", p. 205: > "You may declare the function main as either a function returning an > integer or as a function returning void." Yes, you may. If you want to continue using ORCA/C on a IIgs the rest of your life. But what happens when you port it to a machine that doesn't follow this rule? You know as well as I do that the ORCA/C manual is not the definitive source on C. ----------------- Jeffrey Hutzelman America Online: JeffreyH11 Internet/BITNET:jh4o+@andrew.cmu.edu, jhutz@drycas.club.cc.cmu.edu, jh4o@cmuccvma >> Apple // Forever!!! <<