[PATCH RFC v3 3/5] lib: test-kstrtox: add E notation tests for kstrto[u]dec64()
From: Rodrigo Alencar via B4 Relay
Date: Tue Oct 20 2026 - 08:30:24 EST
From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
Cover E notation parsing in kstrtoudec64() and kstrtodec64(): positive,
zero and negative exponents, upper case 'E', an explicit '+' sign,
rounding (ties to even) of integer digits dropped by negative exponents,
large values, and failures for overflowing and invalid inputs.
Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
---
lib/test-kstrtox.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 72 insertions(+), 1 deletion(-)
diff --git a/lib/test-kstrtox.c b/lib/test-kstrtox.c
index 1f176b232085..5365d020746d 100644
--- a/lib/test-kstrtox.c
+++ b/lib/test-kstrtox.c
@@ -780,7 +780,36 @@ static void __init test_kstrtoudec64_ok(void)
{"0.0000000000000000000012345", 23, 123},
/* rounding with many excess digits */
{"0.00000000000000000000000000000000423", 34, 42},
- {"1.99999999999999999999999999999999999", 3, 2000},
+ /* E notation: positive exponent, no fraction */
+ {"1e3", 3, 1000000ULL},
+ {"42e2", 3, 4200000ULL},
+ /* E notation: positive exponent with fraction */
+ {"2.718e3", 3, 2718000ULL},
+ {"1.5e2", 1, 1500ULL},
+ /* E notation: uppercase E */
+ {"1E3", 3, 1000000ULL},
+ /* E notation: explicit positive exponent sign */
+ {"1e+3", 3, 1000000ULL},
+ /* E notation: zero exponent */
+ {"1.5e0", 1, 15ULL},
+ /* E notation: negative exponent shifts decimal left */
+ {"271828e-5", 3, 2718ULL},
+ {"2.71828e-1", 3, 272ULL},
+ {"270e-2", 3, 2700ULL},
+ /* E notation: negative exponent that rounds integer digits */
+ {"27e-4", 3, 3ULL},
+ {"19e-1", 0, 2ULL},
+ /* E notation: ties to even on integer digits */
+ {"125e-1", 0, 12ULL},
+ {"135e-1", 0, 14ULL},
+ {"25.0001e-1", 0, 3ULL},
+ /* E notation: negative exponent below 1 ULP rounds to 0 */
+ {"1e-5", 3, 0ULL},
+ {"5e-1", 0, 0ULL},
+ {"5e-2", 0, 0ULL},
+ {"6e-1", 0, 1ULL},
+ /* E notation: large value (27 GHz in micro Hz) */
+ {"2.7e10", 6, 27000000000000000ULL},
};
TEST_OK(kstrtoudec64, u64, "%llu", test_udec64_ok);
}
@@ -814,6 +843,17 @@ static void __init test_kstrtoudec64_fail(void)
{"0.2", 20},
{"0.18446744073709551616", 20},
{"1", 20},
+ /* E notation: exponent causes overflow */
+ {"1e21", 1},
+ {"2e20", 1},
+ /* E notation: no digits after exponent marker */
+ {"1e", 3},
+ /* E notation: sign only after exponent marker */
+ {"1e+", 3},
+ {"1e-", 3},
+ /* E notation: misc */
+ {"1ee", 3}, /* double 'e' */
+ {"1e+0b", 3}, /* hex character after exponent */
};
TEST_FAIL(kstrtoudec64, u64, "%llu", test_udec64_fail);
}
@@ -873,6 +913,27 @@ static void __init test_kstrtodec64_ok(void)
{"-0.00000000000000000001", 20, -1},
{"0.009223372036854775807", 21, LLONG_MAX},
{"-0.009223372036854775808", 21, LLONG_MIN},
+ /* E notation: positive number */
+ {"1e3", 3, 1000000LL},
+ {"2.7e3", 3, 2700000LL},
+ {"1.5e0", 1, 15LL},
+ /* E notation: negative number with positive exponent */
+ {"-1e3", 3, -1000000LL},
+ {"-2.7e3", 3, -2700000LL},
+ /* E notation: negative exponent */
+ {"27e-1", 3, 2700LL},
+ {"-27e-1", 3, -2700LL},
+ {"2.7e-1", 3, 270LL},
+ {"-2.7e-1", 3, -270LL},
+ /* E notation: negative exponent rounds integer digits */
+ {"-27e-4", 3, -3LL},
+ {"-125e-1", 0, -12LL},
+ {"-135e-1", 0, -14LL},
+ /* E notation: negative exponent below 1 ULP rounds to 0 */
+ {"1e-5", 3, 0LL},
+ {"-1e-5", 3, 0LL},
+ {"-5e-1", 0, 0LL},
+ {"-6e-1", 0, -1LL},
};
TEST_OK(kstrtodec64, s64, "%lld", test_dec64_ok);
}
@@ -903,6 +964,16 @@ static void __init test_kstrtodec64_fail(void)
{"-0.1", 20},
{"0.09223372036854775808", 20},
{"-0.09223372036854775809", 20},
+ /* E notation: exponent causes overflow */
+ {"1e21", 1},
+ {"-1e21", 1},
+ /* E notation: no digits after exponent marker */
+ {"1e", 3},
+ {"1e+", 3},
+ {"1e-", 3},
+ /* E notation: misc */
+ {"1Ee+3", 3}, /* double 'e' with mixed case */
+ {"1e+0xa", 3}, /* hex number exponent */
};
TEST_FAIL(kstrtodec64, s64, "%lld", test_dec64_fail);
}
--
2.43.0