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Merge pull request #353 from toughengineer/main

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Fixed UB
This commit is contained in:
Daniel Lemire 2025-12-27 12:03:36 -05:00 committed by GitHub
commit 43f7c83a55
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1 changed files with 21 additions and 19 deletions
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40
include/fast_float/ascii_number.h
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@ -523,33 +523,36 @@ parse_int_string(UC const *p, UC const *pend, T &value,
return answer;
}
union {
uint8_t as_str[4];
uint32_t as_int;
} digits;
uint32_t digits;
if (cpp20_and_in_constexpr()) {
digits.as_int = 0;
#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED && FASTFLOAT_HAS_BIT_CAST
if (std::is_constant_evaluated()) {
uint8_t str[4]{};
for (size_t j = 0; j < 4 && j < len; ++j) {
digits.as_str[j] = static_cast<uint8_t>(p[j]);
str[j] = static_cast<uint8_t>(p[j]);
}
} else if (len >= 4) {
memcpy(&digits.as_int, p, 4);
digits = std::bit_cast<uint32_t>(str);
}
#else
if (false) {
}
#endif
else if (len >= 4) {
::memcpy(&digits, p, 4);
} else {
uint32_t b0 = static_cast<uint8_t>(p[0]);
uint32_t b1 = (len > 1) ? static_cast<uint8_t>(p[1]) : 0xFFu;
uint32_t b2 = (len > 2) ? static_cast<uint8_t>(p[2]) : 0xFFu;
uint32_t b3 = 0xFFu;
#if FASTFLOAT_IS_BIG_ENDIAN
digits.as_int = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
digits = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
#else
digits.as_int = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
digits = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
#endif
}
uint32_t magic =
((digits.as_int + 0x46464646u) | (digits.as_int - 0x30303030u)) &
0x80808080u;
((digits + 0x46464646u) | (digits - 0x30303030u)) & 0x80808080u;
uint32_t tz = (uint32_t)countr_zero_32(magic); // 7, 15, 23, 31, or 32
uint32_t nd = (tz == 32) ? 4 : (tz >> 3);
nd = (uint32_t)std::min((size_t)nd, len);
@ -578,18 +581,17 @@ parse_int_string(UC const *p, UC const *pend, T &value,
return answer;
}
digits.as_int ^= 0x30303030u;
digits.as_int <<= ((4 - nd) * 8);
digits ^= 0x30303030u;
digits <<= ((4 - nd) * 8);
uint32_t check = ((digits.as_int >> 24) & 0xff) |
((digits.as_int >> 8) & 0xff00) |
((digits.as_int << 8) & 0xff0000);
uint32_t check = ((digits >> 24) & 0xff) | ((digits >> 8) & 0xff00) |
((digits << 8) & 0xff0000);
if (check > 0x00020505) {
answer.ec = std::errc::result_out_of_range;
answer.ptr = p + nd;
return answer;
}
value = (uint8_t)((0x640a01 * digits.as_int) >> 24);
value = (uint8_t)((0x640a01 * digits) >> 24);
answer.ec = std::errc();
answer.ptr = p + nd;
return answer;