Inside Macintosh: PowerPC Numerics / Part 2 - The PowerPC Numerics C Implementation

Chapter 8 - Environmental Control Functions

Accessing the Floating-Point Environment

MathLib defines four functions that access the entire floating-point environment:

fegetenv	Returns the current environment.
feholdexcept	Saves the previous environment and clears all exception flags.
fesetenv	Sets new environmental values.
feupdateenv	Restores a previously saved environment.

These functions take parameters of type fenv_t. Type fenv_t is the environment word type. In general, the environmental access functions either take a pointer to a variable of type fenv_t or accept the macro FE_DFL_ENV, which defines the default environment (default rounding direction and all exceptions cleared).