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Fix scalblnl() for large long exponents - #363
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Clamp the long exponent to +/-65536 before converting it to int, as in msun, and pass the clamped value to scalbnl(). The previous call discarded the clamp and could turn extreme exponents into unrelated finite results. Add a regression for both signs of 2^32 and LONG_MIN/LONG_MAX, including the floating-point range exceptions.
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On LP64 x86-64 with round-to-nearest,
scalblnl(1.0L, 4294967296L)returns1.0Lwithout exceptions, although C's radix scaling requires positive infinity and overflow. Negating that exponent also returns1.0Linstead of positive zero and underflow.We clamp the exponent to ±65536 before converting it to
intand pass the bounded value toscalbnl(), following FreeBSD's correction.We added a regression and confirmed that it and the standalone reproducer pass, alongside the existing
make testsuite.— ChipLab