I am writting a small project that has to take in account all versions of Standard C, from C89 to C11, trying to ensure some degree of compatibility across versions. In doing this, I found that the Standard Header <float.h> has very different specfications in C89 compared to C99.
In C89, almost all macros in <float.h>, except FLT_RADIX, are not necessarily constant expressions. However, in C99 all macros in <float.h> except FLT_ROUNDS are constant expressions (they can be used, for example, in static initializers).
My guess is that, even in the ancient C89, the expected behaviour for a given conforming implementation is that all macros in <float.h> (except FLT_ROUNDS) has to be unmodifiable values along program execution, even when they cannot be considered syntacticly as constant expressions.
On the other hand, C89 Standard document says (C89 draft, 2.2.4.2):
The floating-point model representation is provided for all values except FLT_ROUNDS.
Here "all values" refers to the list of macros declared in <float.h>.
MY QUESTION: What does it mean in C89 the word provided? Is it right to interpret that the implementation provides values for the macros that are unmodifiable along program execution? Moreover: are they unmodifiable values for the target execution environment?
Thanks in advance.