Is function call a memory barrier?

Question

Consider this C code:

extern volatile int hardware_reg;

void f(const void *src, size_t len)
{
    void *dst = ;

    hardware_reg = 1;    
         


        

Answer 1

As far as I can see your reasoning leading to

the compiler would see no trouble in moving the memcpy call

is correct. Your question is not answered by the language definition, and can only be addressed with reference to specific compilers.

Sorry to not have any more-useful information.