what is “stack alignment”?

Question

What is stack alignment? Why is it used? Can it be controlled by compiler settings?

The details of this question are taken from a problem faced when trying to use

Answer 1

Some CPU architectures require specific alignment of various datatypes, and will throw exceptions if you don't honor this rule. In standard mode, x86 doesn't require this for the basic data types, but can suffer performance penalties (check www.agner.org for low-level optimization tips).

However, the SSE instruction set (often used for high-performance) audio/video procesing has strict alignment requirements, and will throw exceptions if you attempt to use it on unaligned data (unless you use the, on some processors, much slower unaligned versions).

Your issue is probably that one compiler expects the caller to keep the stack aligned, while the other expects callee to align the stack when necessary.

EDIT: as for why the exception happens, a routine in the DLL probably wants to use SSE instructions on some temporary stack data, and fails because the two different compilers don't agree on calling conventions.