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Re: Conflicts between C standard and 754-2008



To Fred Tydeman, who quoted the relevant C99 section:
So, strtod() can do what IEEE-754 requires.

For underflow, yes, but not for overflow:  HUGE_VAL can have only one
value, is the required result on overflow, and yet 754 requires two
different values.

To Vincent Lefèvre, who dug up extra and conflicting information about
directed rounding:  Thank you very much!  So how does one go about
opening a defect against a standard?

Btw, this matters to the IEEE 1788 crowd, where I shall post next.

On hex strings:  based on the adage "be lenient on input and strict on
output" I would say that scanf() (e.g. via strtod()) should accept 0x123
but that printf() should produce 0x123p0 when asked for hex conversion.

As for "0xgarbage", I came to the somewhat unhappy conclusion that it
has to be parsed as a valid "0" terminated by "xgarbage", and will fix
my parser.  Linux seems to do this; AIX actually eats "0x" because it
appears to accept zero given digits (it would eat "0xp-1" too) as the
value zero (which must be seen as a  bug).

Michel.
---Sent: 2011-01-01 03:21:25 UTC


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