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Don't generate zeros and fix UB on huge precision

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This commit is contained in:
Victor Zverovich 2020-09-19 16:01:43 -07:00
parent ce3f76994a
commit 0016da7ab3
1 changed files with 5 additions and 4 deletions
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9
include/fmt/format-inl.h
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@ -2612,10 +2612,7 @@ void fallback_format(Double d, int num_digits, bool binary32, buffer<char>& buf,
if (upper != &lower) *upper *= 10; if (upper != &lower) *upper *= 10;
} }
} }
// Generate the given number of digits up to the maximum possible number of // Generate the given number of digits.
// significant digits in an IEEE754 double.
const int max_double_digits = 767;
if (num_digits > max_double_digits) num_digits = max_double_digits;
exp10 -= num_digits - 1; exp10 -= num_digits - 1;
if (num_digits == 0) { if (num_digits == 0) {
buf.try_resize(1); buf.try_resize(1);
@ -2745,6 +2742,10 @@ int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
const auto cached_pow = get_cached_power( const auto cached_pow = get_cached_power(
min_exp - (normalized.e + fp::significand_size), cached_exp10); min_exp - (normalized.e + fp::significand_size), cached_exp10);
normalized = normalized * cached_pow; normalized = normalized * cached_pow;
// Limit precision to the maximum possible number of significant digits in an
// IEEE754 double because we don't need to generate zeros.
const int max_double_digits = 767;
if (precision > max_double_digits) precision = max_double_digits;
fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed}; fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error) { if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error) {
exp += handler.size - cached_exp10 - 1; exp += handler.size - cached_exp10 - 1;