ajs@hpfcla.UUCP (05/10/84)
> In all seriousness, the more parentheses there are in an > expression, the harder it is to read. I personally find the > layout > y = x == 5 ? 1 : 0; > much clearer than > y = (x == 5) ? 1 : 0; In all seriousness, I wholly, absolutely, irrevocably disagree with you, and hope I never have to maintain any of your code, so there. It's obviously a religious discussion. On the bright side, award yourself two points if you care enough to consider coding standards at all. The only real losers are those who don't even think about it. Alan (we can still agree on something) Silverstein
ok@edai.UUCP (05/22/84)
I never use return(expr) or return (expr) on the grounds that
it looks like a FUNCTION CALL, and it isn't. Most of the time
you are saying return TRUE or return FALSE or return <variable>,
and the extra junk doesn't do anything for you.
Do people who like return(e) also #define Goto(x) goto x
and then write Goto(L), Break(), Continue() and so on? If not,
why not?
I'd prefer keywords like if ... then instead of if (...).
This principle that things which aren't function calls shouldn't
look like function calls has lead me to adopt the practice of
#define skip
while (this_does_everything) skip;
instead of
while (this_does_everything) ;
I apologise for letting code get out into the world without this
readability feature, and promise not to do it again.
In all seriousness, the more parentheses there are in an
expression, the harder it is to read. I personally find the
layout
y = x == 5 ? 1 : 0;
much clearer than
y = (x == 5) ? 1 : 0;
Yes, a policy of avoiding parentheses can make very large expressions
hard to read, but adding unnecessary parentheses only makes it worse;
the answer is to break up big expressions. (That doesn't hurt most
compilers either.)rich@mit-bugs-bunny.arpa (01/25/86)
I'm on a binary only 3b2/300 running SV.2.2 so... What's the difference between leaving main by return() vs exit() vs _exit()? I mean in reality, by proposed standards (X3J11 can you hear me?), and functionally (like on my machine). Who closes file descriptors? Who reclaims memory? What about shared memory? What is a gate 4, 8? K. Richard Magill
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (01/26/86)
> I'm on a binary only 3b2/300 running SV.2.2 so... > > What's the difference between leaving main by return() vs exit() vs _exit()? > I mean in reality, by proposed standards (X3J11 can you hear me?), and > functionally (like on my machine). Who closes file descriptors? Who reclaims > memory? What about shared memory? What is a gate 4, 8? There is no difference between reality and the proposed standards. If main() is left via a return statement, the effect is exactly the same as termination via invocation of exit() with the return value used as the parameter to exit(). exit() is required to flush STDIO output buffers and do any other required cleanup. _exit() directly terminates the process without performing any extra actions along the way. _exit() is not available in all C implementations, although it is required on UNIX systems. "File descriptor" is a UNIX-only concept. Open file descriptors are closed by the UNIX kernel when a process terminates. The kernel is also responsible for memory allocation and sharing. GATE is similar to a subroutine jump except it switches into the kernel (acquires new PC & PSW), vectored through tables indexed by R0 and R1. This constitutes a "service call" or "system call". _exit() is normally implemented as a small piece of assembly- language code that simply invokes the appropriate system call, perhaps "gate 4,8". exit() normally calls _cleanup(), perhaps runs registered onexit handlers, then invokes _exit().
brooks@lll-crg.ARpA (Eugene D. Brooks III) (01/26/86)
In article <178@rexago1.UUCP> rich@rexago1.UUCP (K. Richard Magill) writes: >I'm on a binary only 3b2/300 running SV.2.2 so... > >What's the difference between leaving main by return() vs exit() vs _exit()? return(i) from main is the same as exit(i), exit(i) flushes all the open file descriptors and then calls _exit(i). _exit(i) crashes and burns.
jsdy@hadron.UUCP (Joseph S. D. Yao) (01/26/86)
In article <178@rexago1.UUCP> rich@rexago1.UUCP (K. Richard Magill) writes: >What's the difference between leaving main by return() vs exit() vs _exit()? Functionally, return and exit should be identical. Your 'lint' (s5r2.0v2) prob'ly complains if you use exit() tho. The code goes roughly like: [C header, crt0.s:] push envp push argv push argc call $3, _main push r0 call $1, $_exit sys $exit_system_call halt Note that exit(main(argc, argv, envp)) is the effect. The exit() code resembles: exit(val) int val; { register FILE *fp; for (fp = _iob; fp < &_iob[NIOBUFS]; fp++) if fp has been opened fclose(fp); _exit(val); } .......... __exit: move arg to r0 sys $exit_system_call Shared and local memory are reclaimed by the kernel after an exit() system call. > ... What is a gate 4, 8? Got my curiosity piqued. -- Joe Yao hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}