Hello, I'm thinking about how to implement Fortran 2003's IEEE support in gfortran. The IEEE allow a) To set an IEEE value (NaN, INF, etc.) b) Check whether a value is NaN, etc. c) To query for IEEE capabilities (IEEE_SUPPORT_NAN, IEEE_SUPPORT_SQRT (a sqrt() which has IEEE exception support), etc.) d) To query/set haltmodes for DIVIDE_BY_ZERO, INVALID etc. e) Getting/setting an exception flag, etc.
While (a) and (b) can be easily handled in the front end, I don't see how I can handle the rest efficiently. Most parts are provided by fenv.h, for which I seemingly have to write a wrapper function (in libgfortran) as the typedefs and constants cannot be made available in the front end - or have I missed something? My biggest issue is that I don't see how I can compile-time evaluate the following - or how to evaluate it at all: if (IEEE_SUPPORT_NAN(x)) & ! should be always true (or false) on a given system x = IEEE_VALUE(IEEE_QUIET_NAN, x) ! x = qNaN (trivial in the front end). The Fortran standard lists: IEEE_SUPPORT_DENORMAL, _DIVIDE (by zero), _INF, _NAN, _SQRT (a sqrt which follows IEEE), _ROUNDING, (and _IO). Is there some possibility to query the target whether e.g. NaN is supported? For querying/setting the halting mode, I would work with the data in libgfortran/config/*.h. Tobias
