Estimating Remaining Stack Space in a C Program

The article challenges the common belief that remaining stack space cannot be reliably estimated in C programs. On modern Unix systems (Linux, BSD, macOS), combining stack limits (via getrlimit, pthread_getattr_np, and GCC/Clang constructor attributes) with the current stack pointer allows building a utility function like stack_remaining() to estimate available space. This enables smarter runtime decisions between stack and heap allocation.