The volatile keyword is intended to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler.
Objects declared as volatile are omitted from optimization because their values can be changed by code outside the scope of current code at any time. See Understanding “volatile” qualifier in C for more details.
Can a variable be both const and volatile?
yes, the const means that the variable cannot be assigned a new value. The value can be changed by other code or pointer. For example the following program works fine.
#include <stdio.h>
int main(void)
{
const volatile int local = 10;
int* ptr = (int*)&local;
printf("Initial value of local : %d \n", local);
*ptr = 100;
printf("Modified value of local: %d \n", local);
return 0;
}
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