Local buffer optimization in detail

We have seen the applications of local buffer optimization; for simplicity, we stayed with the most basic implementation of it. This simple implementation misses several important details, which we will now highlight.

First of all, we completely neglected the alignment of the buffer. The type we used to reserve the space inside an object is char; therefore, our buffer is byte-aligned. Most data types have higher alignment requirements: the exact requirements are platform-specific, but most built-in types are aligned on their own size (double is 8-byte-aligned on a 64-bit platform such as x86). Higher alignments are needed for some machine-specific types such as packed integer or floating-point arrays for AVX instructions.

Alignment is important: depending on the processor and the code generated by the compiler, accessing memory not aligned as required by the data type can result in poor performance or memory access violations (crashes). For...