Is the Microsoft Stack always aligned to 16-bytes?

As of my knowledge cutoff date in September 2021, the Microsoft Stack, also known as the x86 Stack, is typically aligned to 4 bytes, not 16 bytes. The stack alignment refers to the requirement that data be stored on the stack at addresses that are multiples of a specific value, often referred to as the "stack alignment boundary." For x86 processors, the stack alignment boundary is 4 bytes.

In x86 architectures, the stack grows downward in memory, and each stack frame typically contains data for function arguments, local variables, and return addresses. The stack pointer (ESP register) is used to keep track of the top of the stack.

However, there are some cases where specific data types or SIMD (Single Instruction, Multiple Data) operations require 16-byte alignment. In these cases, compilers and assemblers can use special alignment directives to ensure that the data is properly aligned on the stack.

Additionally, with the introduction of 64-bit x86 architectures (x86-64 or AMD64), the stack alignment can be increased to 8 bytes to support the larger data types and extended register set of 64-bit processors.

It's essential to note that stack alignment may vary based on the specific compiler, architecture, and target platform. Additionally, future updates or changes to Microsoft's toolchain and libraries may impact the stack alignment behavior. Therefore, it's always a good practice to consult the official documentation and specifications for the specific version of the toolchain you are using to confirm the stack alignment requirements.