-- Manuel A. McLure KE6TAW <mmt@unify.com>
-----Original Message----- From: Richard B. Johnson [mailto:root@chaos.analogic.com] Sent: Wednesday, May 05, 1999 12:11 PM To: Steve VanDevender Cc: linux-kernel@vger.rutgers.edu Subject: Re: fork() Problem?
On Wed, 5 May 1999, Steve VanDevender wrote:
> Richard B. Johnson writes: > > > if (pid = fork()) > > ^^^^________ logical test of an assignment? This will always > > be true! > > No. An assignment expression has the value of the value > assigned. This allows expressions like a = b = c ('=' is > right-associative). It will be true if the assigned value is > true (nonzero), and false if the assigned value is false (zero). > > However, it is generally more clear and less error prone to make > such tests explicit (i.e. (a = b) != 0). >
No. Definitely not! The gcc compiler 'fixes' very obvious and awful bugs.
#include <stdio.h>
int foo() { return 0; }
int main() { int i; if(i=foo()) (void)puts("If this is not seen, it is a compiler BUG!");
return 0; }
LCLint 2.2a --- 04 Sep 96
xxx.c: (in function main) xxx.c:13,5: Test expression for if is assignment expression: i = foo() The condition test is an assignment expression. Probably, you mean to use == instead of =. If an assignment is intended, add an extra parentheses nesting (e.g., if ((a = b)) ...) to suppress this message. (-predassign will suppress message) xxx.c:13,5: Test expression for if not bool, type int: i = foo() Test expression type is not boolean or int. (-predboolint will suppress message)
Finished LCLint checking --- 2 code errors found
I started to notice sloppy code being written this way several years ago when 'gcc' started to allow it. Just because 'gcc' fixes bad code doesn't mean it's the way to go (unless it fixes the source at the same time).
Cheers, Dick Johnson ***** FILE SYSTEM WAS MODIFIED ***** Penguin : Linux version 2.2.6 on an i686 machine (400.59 BogoMips). Warning : It's hard to remain at the trailing edge of technology.
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