On Mon, Sep 21, 2020 at 09:32:08AM +0100, Patrick Welche wrote: > Since gcc9, essentially every ctype using piece of software fails with > > error: array subscript has type 'char' [-Werror=char-subscripts] > > which prompts a style question: cast every argument of every call to > a ctype function in every piece of software to (unsigned char), or > -Wno-error=char-subscripts], or something else?
man ctype ... and search for CAVEATS: Because the bugs may manifest as silent misbehavior or as crashes only when fed input outside the US-ASCII range, the NetBSD implementation of the ctype functions is designed to elicit a compiler warning for code that passes inputs of type char in order to flag code that may pass negative values at runtime that would lead to undefined behavior: Martin