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V2663. MISRA. The macro EOF should only be compared with the unmodified return value of any Standard Library function capable of returning EOF.
This diagnostic rule is based on the MISRA (Motor Industry Software Reliability Association) software development guidelines.
This diagnostic rule is relevant only for C.
Certain standard library functions use the return EOF value to indicate the end-of-file stream state or input/output errors. The return values of these functions should not undergo conversion or type casting operations before being compared to EOF.
The example:
#define EOF (-1);
//....
int i = (char)getchar();
if (EOF != i)
{
//....
}The getchar function returns a value of int type in the range of 0 to 255 or -1 (EOF). The resulting value is converted to char type and assigned to a variable of int type. With this conversion, the character with the 0xFF (255) value will turn into -1 and will be interpreted exactly the same as the end-of- file macro constant (EOF).
The fixed code:
#define EOF (-1);
//....
int i = getchar();
if (EOF != i)
{
//....
}To avoid such errors, use alternative functions feof for the end-of-file stream state check or ferror for reading errors. These functions directly check the stream descriptor and are not affected by type conversion operations.
The example:
while (!feof(stdin))
{
char ch;
ch = (char)getchar();
//....
}Was this page helpful?
