Synopsis

Do not add or subtract a scaled integer to a pointer.

Enabled by default

Yes

Severity/Certainty

High/Medium

Full description

When performing pointer arithmetic, the size of the value to add to or subtract from a pointer is automatically scaled to the size of the type of the referenced array object. Adding or subtracting a scaled integer value to or from a pointer is invalid because it may yield a pointer that does not point to an element within or one past the end of the array.

Coding standards

Code examples

The following code example fails the check and will give a warning:

enum { INTBUFSIZE = 80 };

extern int getdata(void);
int buf[INTBUFSIZE];

void func(void) {
    int *buf_ptr = buf;

    while (buf_ptr < (buf + sizeof(buf))) {
        *buf_ptr++ = getdata();
    }
}

The following code example passes the check and will not give a warning about this issue:

enum { INTBUFSIZE = 80 };

extern int getdata(void);
int buf[INTBUFSIZE];

void func(void) {
    int *buf_ptr = buf;

    while (buf_ptr < (buf + INTBUFSIZE)) {
        *buf_ptr++ = getdata();
    }
}