Daan De Meyer
d52c8f2068
exp10() has a symbol version > 2.34 on latest glibc. To allow dropping our baseline required glibc runtime version to <= 2.34, let's add our own version to prevent pulling in the newer symbol from glibc.
25 lines
963 B
C
25 lines
963 B
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include "math-util.h"
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double xexp10i(int n) {
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/* Powers of 10 up to 10^22 are exact in IEEE-754 binary64. */
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static const double table[] = {
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1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10, 1e11,
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1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22,
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};
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bool negative = n < 0;
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/* Cast before negation so n == INT_MIN doesn't invoke signed-overflow UB. Unsigned negation
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* wraps to the magnitude we want. */
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unsigned k = negative ? -(unsigned) n : (unsigned) n;
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/* 10^309 already overflows binary64 to +Inf; anything beyond just stays there. */
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k = MIN(k, 309u);
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double r = k < ELEMENTSOF(table) ? table[k] : table[ELEMENTSOF(table) - 1];
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for (unsigned i = ELEMENTSOF(table) - 1; i < k; i++)
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r *= 10.0;
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return negative ? 1.0 / r : r;
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}
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