huge error for pow

Paul Zimmermann
Tue Feb 7 14:27:42 GMT 2023


while testing Newlib 4.3.0, I noticed the following huge error:

zimmerma@salade:~/svn/tbd/20/src/binary64$ VERBOSE=-v ./doitb.newlib pow 1000
Checking pow with newlib-
Using seed 1619945
pow 0 -1 -0x1.647ff80007ff8p-576,-0x1.3d018267f12fp+48 [inf] inf inf
libm gives inf
mpfr gives -inf

The exponent y in x^y is a large odd integer, thus since x is negative we
should get a negative number as result.

This issue was apparently already present in 3.3.0, but we only discovered
it now.

Best regards,

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