Paul Schlie wrote:
Just as:
volatile int* port = (int*)PORT_ADDRESS;
int input = *port; supposedly invoking an undefined behavior.
is required to be well specified, effectively reading through a pointer
an un-initialized object's value, and then assigning that unspecified value
to the variable input; as otherwise the language couldn't be utilized to
write even the most hardware drivers required of all computer systems.
Now, wait just a minute here! Doesn't C's definition of "volatile"
specify that things outside the program can cause the value of a
volatile variable to become "determinate"? It's an obvious part of what
the term means, and Fortran's definition of volatile variables most
certainly includes the equivalent provision.
Thus, this code is _not_ invoking an undefined behavior if something
outside the program is causing *port to become determinate (and if the C
standard defines "volatile" in a reasonable way).
- Brooks
