Conversation

With 64 bit address spaces, thread stacks should have GBs reserved by default, and programming with alloca should be encouraged. A lot of string and container work could be done at high performance with alloca and no frees if you don't let them escape.

545

Replying to

Gotta love the man page. Don't get carried away. "The alloca() function returns a pointer to the beginning of the allocated space. If the allocation causes stack overflow, program behavior is undefined"

Old Man Yells At Cloud Provider

Replying to

and

Surely touching anything outside the stack limit would result in a page fault, no?

Replying to

and

It depends on the platform including the OS and compiler. You need -fstack-clash-protection with Clang and GCC on Linux to guarantee stack overflows are detected. Otherwise, you can easily skip over the guard page. It's not inherently caught from going past the end of the stack.

Touisteur EmporteUneVache

Replying to

Never quite understood the difference between that and -fstack-check?

Replying to

GCC -fstack-check doesn't provide protection in the general case and is actively dangerous on architectures without new-style checking. Clang doesn't actually implement it. -fstack-clash-protection is safe and provides full protection on architectures with proper support for it.

7:49 AM · May 2, 2021Twitter Web App

Replying to

MSVC++ and Clang with the proper Windows ABI always have full protection from the issue since the Windows ABI has taken care of this properly for ages. MinGW is unsafe in general and lacks multiple protections + has flawed implementations. It probably gets this wrong too...