Function get_prompt

3rd/lua-5.4.3/src/lua.c:443–451

** Return the string to be used as a prompt by the interpreter. Leave ** the string (or nil, if using the default value) on the stack, to keep ** it anchored. */

** it anchored.
*/
static const char *get_prompt (lua_State *L, int firstline) {
  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
    return (firstline ? LUA_PROMPT : LUA_PROMPT2);  /* use the default */
  else {  /* apply 'tostring' over the value */
    const char *p = luaL_tolstring(L, -1, NULL);
    lua_remove(L, -2);  /* remove original value */
    return p;
  }
}

/* mark in error messages for incomplete statements */
#define EOFMARK		"<eof>"