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Fix js_atod rounding when input has more than max_digits significant digits #506

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Fix js_atod rounding when input has more than max_digits significant digits #506

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6 changes: 4 additions & 2 deletions dtoa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1505,8 +1505,10 @@ double js_atod(const char *str, const char **pnext, int radix, int flags,
}

/* Use the extra digits for rounding if the base is a power of
two. Otherwise they are just truncated. */
if (radix_bits != 0 && extra_digits != 0) {
two. Otherwise use them as a sticky bit so that round-half-to-even
rounds correctly when there are non-zero digits beyond the
precision we kept. */
if (extra_digits != 0) {
tmp0->tab[0] |= 1;
}

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6 changes: 6 additions & 0 deletions tests/test_builtin.js
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Expand Up @@ -398,6 +398,12 @@ function test_number()

assert((1.3).toString(7), "1.2046204620462046205");
assert((1.3).toString(35), "1.ahhhhhhhhhm");

/* parsing must use digits beyond max_digits as a sticky bit so
that round-half-to-even rounds in the correct direction.
https://github.com/bellard/quickjs/issues/452 */
assert(+"100000000000000000000000.000000000000001",
1.0000000000000001e+23);
}

function test_eval2()
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