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Guard fast decimal path on bit width instead of byte size

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Use num_bits<UInt>() == 32 instead of sizeof(UInt) == 4 in
do_format_decimal. The magic-number two-digit algorithm requires
exactly 32 value bits, so this is more precise on platforms where
CHAR_BIT != 8 and is consistent with existing num_bits<T>() usage.
This commit is contained in:
Victor Zverovich 2026-07-11 09:17:57 -07:00
parent 9d13c41ce6
commit 7077b016cc
1 changed files with 1 additions and 1 deletions
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2
include/fmt/format.h
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@ -1234,7 +1234,7 @@ FMT_CONSTEXPR20 auto do_format_decimal(Char* out, UInt value, int size)
unsigned n = to_unsigned(size);
while (value >= 100) {
n -= 2;
if (!is_constant_evaluated() && sizeof(UInt) == 4) {
if (!is_constant_evaluated() && num_bits<UInt>() == 32) {
auto p = value * static_cast<uint64_t>((1ull << 39) / 100 + 1);
write2digits_i(out + n, p >> (39 - 7) & ((1 << 7) - 1));
value = static_cast<UInt>(p >> 39) +