How to say there is a struct of this type at this memory location?

[Timo Sintonen via D.gnu]

On Monday, 7 March 2016 at 21:12:02 UTC, Taylor Hillegeist wrote:
> I'm working on getting my FRDM-kl25z board up and running with 
> d. whatever works at this point.
>
> The issue is when i try to specify hey this struct is over 
> here! using:
>
> __gshared SIM_MemMap  * SIMY       = cast(SIM_MemMap *) 
> 0x40047000;
> __gshared PORT_MemMap * TMP2CH     = cast(PORT_MemMap*) 
> 0x4004A000;
> __gshared PORT_MemMap * TMP0CH     = cast(PORT_MemMap*) 
> 0x4004C000;
> __gshared TPM_MemMap  * TPM0       = cast(TPM_MemMap *) 
> 0x40038000;
> __gshared TPM_MemMap  * TPM2       = cast(TPM_MemMap *) 
> 0x4003A000;
> __gshared SCB_MemMap  * SCB        = cast(SCB_MemMap *) 
> 0xE000E000;
>
> and then try an set values:
>
> SIMY.COPC = 0; //DISABLE WATCHDOG TIMER;
>
> it looks like someone moves my cheese when i run in the 
> simulator (uvision)
>
> SIMY actual address ends up being 0x1FFFF0C4;
>
> http://dpaste.dzfl.pl/20c95c182f6c
>
> the whole projects is two files a linker and the file above. i 
> switched from LDC because i couldn't get the section attribute 
> working on 0.14.
> Any help would be appreciated thanks!

I make it this way:
shared (uartreg*) uart2=cast (shared(uartreg*))0x40004400;

See for example
https://bitbucket.org/timosi/minlibd/src/61039fcbbf5845c7f18370c30857cfc034241fa2/tools/main/uart.d?at=default&fileviewer=file-view-default

Then I mark all individual registers as ahared too.

The compiler may optimize register accesses when it thinks they 
are not necessary. For example, if there are multiple writes to 
the same register, the compiler may remove all but the last. 
Repetitive reads, like status poll may be optimized to be done 
just once.

Gdc treats all shared variables as volatile and marking all 
struct members shared solves the problem partially. However this 
is unstable and buggy feature and may be removed in future.