Is there any definition how floating-point values evaluated at compile-time are rounded?

Question

Is there any definition how floating-point values evaluated at compile-time are rounded in C or C++ ? Fe when I have "double d = 1.0 / 3.0;" ? Ie what kind of rounding is done at compile-time.

And is there a definition of what's the default-rounding mode for a thread at runtime (C99's / C++11's fegetround() / fesetround()) ?

And is rounding to integer-values also included in the latter configuration parameters ? Im aware of nearbyint(), but this is specified to bound to the rounding-parameters which can be set by fesetround(). What I'm concerned about is direct casting to an integer.

Answer 1

In both specs (C17 and C++20), the compile time rounding is implementation defined.

The C spec recommends that translation time conversion should match execution time conversion by library functions (like strtod ) but it is not required.