On Fri, 17 Sep 2021, Jorg Brown via Liaison wrote:
> Re: "strfromf128", is that documented anywhere?  N1312 doesn't mention it
> and Google is surprisingly unhelpful... I presume it's just
> https://man7.org/linux/man-pages/man3/strfromd.3.html but with added types?

You should be using
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2596.pdf as the current
C23 working draft, which documents strfromd, strfromf and strfroml (and
corresponding strfromd32, strfromd64, strfromd128).

Jorg Brown wrote:

 >> That's problematic, depending on the overload-resolution rules for the new floating-point types. 

>> [… example with intN_t types …]

 

In the early days of P1467 there was a vigorous debate about whether the std::floatN_t types could be typedefs of standard types or not.  People pointed out the problems that the interactions between the intN_t types and overloading, and that argument won the day.  The std::floatN_t types must be different types than float, double, or long double, similar to how the _FloatN types are different type than float, double, or long double in C.  It will be possible to have overloads of both float and std::float32_t.  The exact details of overload resolution in P1467 are still being worked out, but overload sets on floating-point types will not run into the same problems that overload sets on integral types currently do.

>> for my purposes I'd want something that corresponded to std::float16, not necessarily _Float16.

 

std::float16_t in C++ and _Float16 in C are required to have the same representation and same sets of values.  If your implementation defines the FLT16_* macros in <float.h>, then you can use them for std::float16_t.  Or you could get the information via std::numeric_limits<std::float16_t>.  P1467 does not require that C++ implementations define the FLT16_* macros.  Those macros will eventually make their way to C++ when the C++ standard library rebases on top of C23.