gcc: Floating point implementation

1 
1 4.6 Floating Point
1 ==================
1 
1    * 'The accuracy of the floating-point operations and of the library
1      functions in '<math.h>' and '<complex.h>' that return
1      floating-point results (C90, C99 and C11 5.2.4.2.2).'
1 
1      The accuracy is unknown.
1 
1    * 'The rounding behaviors characterized by non-standard values of
1      'FLT_ROUNDS' (C90, C99 and C11 5.2.4.2.2).'
1 
1      GCC does not use such values.
1 
1    * 'The evaluation methods characterized by non-standard negative
1      values of 'FLT_EVAL_METHOD' (C99 and C11 5.2.4.2.2).'
1 
1      GCC does not use such values.
1 
1    * 'The direction of rounding when an integer is converted to a
1      floating-point number that cannot exactly represent the original
1      value (C90 6.2.1.3, C99 and C11 6.3.1.4).'
1 
1      C99 Annex F is followed.
1 
1    * 'The direction of rounding when a floating-point number is
1      converted to a narrower floating-point number (C90 6.2.1.4, C99 and
1      C11 6.3.1.5).'
1 
1      C99 Annex F is followed.
1 
1    * 'How the nearest representable value or the larger or smaller
1      representable value immediately adjacent to the nearest
1      representable value is chosen for certain floating constants (C90
1      6.1.3.1, C99 and C11 6.4.4.2).'
1 
1      C99 Annex F is followed.
1 
1    * 'Whether and how floating expressions are contracted when not
1      disallowed by the 'FP_CONTRACT' pragma (C99 and C11 6.5).'
1 
1      Expressions are currently only contracted if '-ffp-contract=fast',
1      '-funsafe-math-optimizations' or '-ffast-math' are used.  This is
1      subject to change.
1 
1    * 'The default state for the 'FENV_ACCESS' pragma (C99 and C11
1      7.6.1).'
1 
1      This pragma is not implemented, but the default is to "off" unless
1      '-frounding-math' is used in which case it is "on".
1 
1    * 'Additional floating-point exceptions, rounding modes,
1      environments, and classifications, and their macro names (C99 and
1      C11 7.6, C99 and C11 7.12).'
1 
1      This is dependent on the implementation of the C library, and is
1      not defined by GCC itself.
1 
1    * 'The default state for the 'FP_CONTRACT' pragma (C99 and C11
1      7.12.2).'
1 
1      This pragma is not implemented.  Expressions are currently only
1      contracted if '-ffp-contract=fast', '-funsafe-math-optimizations'
1      or '-ffast-math' are used.  This is subject to change.
1 
1    * 'Whether the "inexact" floating-point exception can be raised when
1      the rounded result actually does equal the mathematical result in
1      an IEC 60559 conformant implementation (C99 F.9).'
1 
1      This is dependent on the implementation of the C library, and is
1      not defined by GCC itself.
1 
1    * 'Whether the "underflow" (and "inexact") floating-point exception
1      can be raised when a result is tiny but not inexact in an IEC 60559
1      conformant implementation (C99 F.9).'
1 
1      This is dependent on the implementation of the C library, and is
1      not defined by GCC itself.
1