On 2014-02-24 16:07, David Brown wrote:
extern const int const_var; > >GCC will read the value of const_var again after a compiler memory >barrier (e.g. __asm__ volatile("" ::: "memory")).That's the rules - a "memory clobber" says that/any/ memory may change, and things read from memory could change and must therefore be re-read. Specifying the extern var as "const" does not tell the compiler that the value is constant - it simply tells the compiler that/you/ promise not to change it. (It would be nice if C, or at least gcc, had a way to say that the value is never changed, but it does not.)
These variables go into the .rodata section. It seems a bit over paranoid to assume that they change. In my case the .rodata section is a read-only region covering a NOR flash, so its unlikely to change.
-- Sebastian Huber, embedded brains GmbH Address : Dornierstr. 4, D-82178 Puchheim, Germany Phone : +49 89 189 47 41-16 Fax : +49 89 189 47 41-09 E-Mail : sebastian.huber@xxxxxxxxxxxxxxxxxx PGP : Public key available on request. Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
