Add some more comments on WASM_STACK_GUARD_SIZE (bytecodealliance#3341)

Signed-off-by: victoryang00 <[email protected]>

Author: yamt

core/config.h

@@ -455,9 +455,11 @@
  * WASM_STACK_GUARD_SIZE needs to be large enough for:
  *
  * - native functions
+ *
  *   w/o hw bound check, the overhead (aot_call_function etc) + the native
  *   function itself. as of writing this, the former is about 1000 bytes
  *   on macOS amd64.
+ *
  *   with hw bound check, theoretically, only needs to cover the logic to
  *   set up the jmp_buf stack.
  *
@@ -466,9 +468,20 @@
  *
  * - w/o hw bound check, the intepreter loop
  *
+ *   the classic interpreter wasm_interp_call_func_bytecode alone
+ *   seems to consume about 2600 bytes stack.
+ *   (with the default configuration for macOS/amd64)
+ *
+ *   libc snprintf (used by eg. wasm_runtime_set_exception) consumes about
+ *   1600 bytes stack on macOS/amd64, about 2000 bytes on Ubuntu amd64 20.04.
+ *
  * - stack check wrapper functions generated by the aot compiler
  *   (--stack-bounds-checks=1)
  *
+ *   wamrc issues a warning
+ *   "precheck functions themselves consume relatively large amount of stack"
+ *   when it detects wrapper functions requiring more than 1KB.
+ *
  * Note: on platforms with lazy function binding, don't forget to consider
  * the symbol resolution overhead on the first call. For example,
  * on Ubuntu amd64 20.04, it seems to consume about 1500 bytes.