I have some memory mapped hardware in my arm controller.
I define struct regs to describe the registers and __gshared
regs* p to point to the actual address.
I have a loop like: while (p.status==0) {...}
The body of the loop does not touch status and so gdc optimizer
does not evaluate status again, resulting to an endless loop. Gcc
does the same, unless the variable is defined as volatile.
This is ok in tls variables, but gshared variables are not thread
safe. Actually I can see from assembler code that this occurs in
all shared variables, like:
__gshared int a=0;
while (a==0) {}
with nothing in the body generates just a jump to itself and the
program stops.
Another thread, interrupt or hardware can change a __gshared
variable any time, so I think that the evalution should not be
optimized away.
Another related question: is there a way to make the pointer p
immutable but leave the data mutable? The pointer is always set
to the fixed address of the hardware, but making the pointer
const makes also the data immutable.
