This compiler option causes the compiler to emit a call to a stack probe function to ensure that a sufficient amount of stack space is available.
Rather than just probe once for each stack page used, you can substitute a function that *FILLS* the stack frame with a particular value - something like 0xBAADF00D - one could set the value to anything you wanted at runtime.
This would get you similar behaviour to gcc/clang's -ftrivial-auto-var-init
Windows has started to auto-initialize most stack variables in the Windows kernel and several other areas.
The following types are automatically initialized:
Scalars (arrays, pointers, floats)
Arrays of pointers
Structures (plain-old-data structures)
The following are not automatically initialized:
Volatile variables
Arrays of anything other than pointers (i.e. array of int, array of structures, etc.)
Classes that are not plain-old-data
During initial testing where we forcibly initialized all types of data on the stack we saw performance regressions of over 10% in several key scenarios.
With POD structures only, performance was more reasonable. Compiler optimizations to eliminate redundant stores (both inside basic blocks and between basic blocks) were able to further drop the regression caused by POD structures from observable to noise-level for most tests.
We plan on revisiting zero initializing all types (especially now that our optimizer has more powerful optimizations), we just haven’t gotten to it yet.