3.2 Memory Model

Memory accesses by multiple threads to the same variable without synchronization are not necessarily atomic with respect to each other. Several implementation-dependent and application-dependent factors affect whether accesses are atomic. Some variables might be larger than the largest atomic memory operation on the target platform. Some variables might be misaligned or of unknown alignment and the compiler or the runtime system might need to use multiple loads/stores to access the variable. Sometimes there are faster code sequences that use more loads/stores.