[stackghost]

alloca()'s availability and correctness/bugginess is platform dependent, so it probably sees only niche usage since it's not portable. Furthermore, even its man page discourages its use in the general case:

>The alloca() function is machine- and compiler-dependent. Because it allocates from the stack, it's faster than malloc(3) and free(3). In certain cases, it can also simplify memory deallocation in applications that use longjmp(3) or siglongjmp(3). Otherwise, its use is discouraged.

Furthermore:

>The alloca() function returns a pointer to the beginning of the allocated space. If the allocation causes stack overflow, program behavior is undefined.

https://man7.org/linux/man-pages/man3/alloca.3.html