The explicit binary exponent stopped accumulating near 1e9 while the
digits add 4 per character without bound, so a subject with a few
hundred million digits was classified against the wrong exponent:
0x1 followed by 3e8 zeros and p-1200000005000 kept errno, and a long
zero fraction with p+1000000000000 underflowed instead of overflowing.
Saturate the explicit exponent at 2^62, beyond what any addressable
digit run can offset, so the sum never overflows or changes sign.
Record that _Stod and _Stodx follow the title libc.prx rule for
hexadecimal underflow, unverified for libSceLibcInternal.
Refs #9691
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Classify hexadecimal strtod and wcstod input from its own digits rather
than a long double approximation. As measured on God of War Ragnarok's
bundled libc.prx, ERANGE is set only on overflow or when the exact value
is below 2^-1074, and a value between 2^-1075 and 2^-1074 becomes the
smallest subnormal only from 2^-1075 * (1 + 2^-52) up.
Refs #9691
Co-Authored-By: Claude Opus 5.5 <[email protected]>
