On 06-12-2012 19:38, Iain Buclaw wrote:
On 6 December 2012 18:30, Alex Rønne Petersen <a...@lycus.org> wrote:
On 06-12-2012 19:28, Timo Sintonen wrote:
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.
Yes, the compiler *must* assume that anything __gshared is implicitly
volatile in the C sense.
Is this going off your word or mine.... I know as a fact gdc marks
shared decls as volatile, but not __gshared. This was brought into
question once when I pointed it out to you, are you now in agreement?
Regards,
I think it was shared declarations that I didn't think needed volatile,
but __gshared definitely does (I think Walter agrees on the latter too,
not sure about the former).
--
Alex Rønne Petersen
a...@lycus.org
http://lycus.org
