On 30/01/2021 00:13, Guy Sotomayor via cctalk wrote:
In a lot of industry standard coding practices (MISRA, CERT-C) that
type of statement is prohibited and *will* result in an error being
reported by the checker/scanner.
The if statement in your example has at least 2 errors from MISRA's
perspective:
* assignment within a conditional statement
* the conditional not being a boolean type (that is you can't assume 0
is false and non-0 is true...you actually need to compare...in this
case against NULL)
On 1/29/21 3:59 PM, Fred Cisin via cctalk wrote:
On Fri, 29 Jan 2021, Chuck Guzis via cctalk wrote:
In the past (and occasionally today, I use the following construct:
FILE *myfile;
if ( !(myfile = fopen( filename, "r"))
{
fprintf( stderr, "Couldn\'t open %s - exiting\n", filename);
exit (1);
}
Yes, it only saves a line, but neatly describes what's being done.
--Chuck
Yes.
That is another excellent example of where you DO want to do an
assignment AND a comparison (to zero). A better example than my
strcpy one, although yours does not need to save that extra line, but
a string copy can't afford to be slowed down even a little.
That is why it MUST be a WARNING, not an ERROR.
Of course, the error is when that wasn't what you intended to do.
I'm pretty sure that while modern compilers will correctly complain
about an assignment in a conditional, they also recognise the idiom and
don't warn when the extra set of brackets is present. So when you really
do want an assignment and a conditional all in one go, you use the extra
set of brackets and everyone (you, the compiler, future you) know that
you really meant it.
Antonio
--
Antonio Carlini
anto...@acarlini.com
