https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111021
--- Comment #8 from Hans-Peter Nilsson <hp at gcc dot gnu.org> --- (In reply to Kewen Lin from comment #6) > > btw, thanks for the suggestion on "defaulting to NULL or something" in ML, > but I guess a default value like zero rather than ERROR_MARK has to base on > the assertion that the default value is equal to ERROR_MARK, IMHO it isn't > quite maintainable. I believe you could add a code_helper constructor for another type, maybe even "int"? Then the "default" value for the code_helper argument for the legitimate address hook function would just look like "code_helper = 0". Maybe that's too error-prone and a pointer-type or some entirely different type would be better. I might have misunderstood things of course, but that's what I mean by "or something".