Comment by JdeBP
5 years ago
No it would not. Think about what the function would see as its format string in both cases.
The root cause here isn't formatting or scanned items. It is C library implementations that implement the "s" versions of these functions by turning the input string into a nonce FILE object on every call, which requires an initial call to strlen() to set up the end of read buffer point. (C libraries do not have to work this way. Neither P.J. Plauger's Standard C library nor mine implement sscanf() this way. I haven't checked Borland's or Watcom's.)
Yes, it looks that way. On the unix/linux side of things, glibc also implements scanf() by converting to a FILE* object, as does the OpenBSD implementation.
It looks like this approach is taken by the majority of sscanf() implementations!
I honestly would not personally have expected sscanf() to implicitly call strlen() on every call.