On 09/06/2010 22:52, Joerg Wunsch wrote:
As David Brown wrote:
Eric suggested making "some_temp_variable" volatile, which is the
traditional way to enforce ordering in C programming. Strictly
speaking, you don't have to make it volatile - it's enough to make
sure it is in memory if cli() and sei() have memory blocks.
Yes, but again: forcing the variable into memory is a pessimization.
It's not required for the job, but something like that is currently
the only way to force the compiler into doing what the programmer
intended.
Pretending to use the variable in an assembly statement should also
work, with no extra code generated. The syntax is slightly ugly, but it
could be wrapped in a macro:
#define forceGenerate(x) asm volatile("" :: "r" (x))
I can't think of any way to automate this with changes to the cli()
macro, but that's not surprising as the C language doesn't have the
relevant concepts.
If you have a code snippet that shows this sort of re-ordering, it would
be nice to try it with the above macro and see if it fixes the problem.
(suggested language extension)
I'm not sure there is any way to give a solid definition of the
semantics of "volatile" here. And I suspect that you'll have
/slightly/ more difficulty getting this into mainline gcc than for
other extensions such as 0b binary constants...
Yeah, sure. No, this won't be me to implement it...
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