Question

Help me understand this statement:

static int  ** volatile ptr

Please let me know how to analyze this pointer statement.

Answer 1

To address the title text after inserting markers into it: 4(static int 3( * 2( * 1(volatile ptr))). Working inside out:

1: Variable that is free to change at run time for reasons the program may not be aware of. Popular causes are other threads, signals or other events, and pointers to “memory” that is really hardware controllers, etc. Stops compilers/optimizers from emitting code that can fail under such changes.

2: Volatile pointer to this memory. What is pointed to is not volatile.

3: pointer to pointer, or array of pointers. Think char **argv; Again, not volatile.

4: static: this depends on where in the declaration is found:

• outside any function: the ptr value only has compile scope.
• inside a function: the memory will be shared by all calls and/or threads to the function. Allocated just once at compile time.

Interesting: const volatile indicates external influences can change the pointer but your software can not do so.