APL\360

[Guy Sotomayor]

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.
>
-- 
TTFN - Guy