Hi,
I'm contemplating using D for an embedded project where system
configuration registers have fixed memory locations.
One way of doing it would be to have a constant pointer to a structure
with manually aligned members that match the register map, and access
them like that. This becomes cumbersome, as all accesses look like
struct Regs {
...
};
Regs* cfg = cast(Regs*)0xF00;
cfg.reg0 = ...
This is also where D's const-transitivity becomes problematic. Since
the configuration registers are not going anywhere, ideally you'd want
a way of telling the compiler that the *pointer* is constant, but not
the pointed-to stuff.
For a systems language, this seems like a serious drawback. Why can't
I tell the compiler that noone should muck with the cfg pointer's
value? I presume there can be ways around it via delegates, but this
seems like a C++ approach: instead of making it simple, it becomes
convoluted...
OTOH, there's a C hack that allows you to access variables at fixed
memory locations "directly":
#define CFGREG0 (*(unsigned short*)0xBEEF)
I'm an absolute noob to D, and so far I found no way of approximating
this behavior -- of bringing the configuration registers at a fixed
memory location into the scope as an identifier that can be used naked, like
CFGREG0 = 0xFF;
if (CFGREG0 != 3) { ... }
Any hints?
Cheers, Kuba