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Fix integer overflow when using max int precision

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This commit is contained in:
Victor Zverovich 2020-10-07 10:58:46 -07:00
parent 7b50dc0b24
commit 3541880efd
1 changed files with 22 additions and 19 deletions
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41
include/fmt/format.h
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@ -1729,15 +1729,17 @@ OutputIt write_float(OutputIt out, const buffer<char>& significand, int exp,
float_specs specs, Char decimal_point) { float_specs specs, Char decimal_point) {
const char* digits = significand.data(); const char* digits = significand.data();
int num_digits = static_cast<int>(significand.size()); int num_digits = static_cast<int>(significand.size());
int full_exp = exp + num_digits; exp += num_digits;
auto format = specs.format;
if (format == float_format::general &&
!(full_exp >= -3 &&
full_exp < (specs.precision > 0 ? specs.precision : 16) + 1)) {
format = float_format::exp;
}
const Char zero = static_cast<Char>('0'); const Char zero = static_cast<Char>('0');
if (format == float_format::exp) {
auto use_exp_format = [=]() {
if (specs.format == float_format::exp) return true;
if (specs.format != float_format::general) return false;
const int exp_threshold = -4; // Prefer 0.0001 to 1e-04.
return exp - 1 < exp_threshold ||
exp - 1 >= (specs.precision > 0 ? specs.precision : 17);
};
if (use_exp_format()) {
// Insert a decimal point after the first digit and add an exponent. // Insert a decimal point after the first digit and add an exponent.
*out++ = static_cast<Char>(*digits); *out++ = static_cast<Char>(*digits);
int num_zeros = specs.precision - num_digits; int num_zeros = specs.precision - num_digits;
@ -1746,17 +1748,18 @@ OutputIt write_float(OutputIt out, const buffer<char>& significand, int exp,
if (num_zeros > 0 && specs.showpoint) if (num_zeros > 0 && specs.showpoint)
out = std::fill_n(out, num_zeros, zero); out = std::fill_n(out, num_zeros, zero);
*out++ = static_cast<Char>(specs.upper ? 'E' : 'e'); *out++ = static_cast<Char>(specs.upper ? 'E' : 'e');
return write_exponent<Char>(full_exp - 1, out); return write_exponent<Char>(exp - 1, out);
} }
if (num_digits <= full_exp) {
if (num_digits <= exp) {
// 1234e7 -> 12340000000[.0+] // 1234e7 -> 12340000000[.0+]
out = copy_str<Char>(digits, digits + num_digits, out); out = copy_str<Char>(digits, digits + num_digits, out);
out = std::fill_n(out, full_exp - num_digits, zero); out = std::fill_n(out, exp - num_digits, zero);
if (specs.showpoint) { if (specs.showpoint) {
*out++ = decimal_point; *out++ = decimal_point;
int num_zeros = specs.precision - full_exp; int num_zeros = specs.precision - exp;
if (num_zeros <= 0) { if (num_zeros <= 0) {
if (format != float_format::fixed) *out++ = zero; if (specs.format != float_format::fixed) *out++ = zero;
return out; return out;
} }
#ifdef FMT_FUZZ #ifdef FMT_FUZZ
@ -1765,22 +1768,22 @@ OutputIt write_float(OutputIt out, const buffer<char>& significand, int exp,
#endif #endif
out = std::fill_n(out, num_zeros, zero); out = std::fill_n(out, num_zeros, zero);
} }
} else if (full_exp > 0) { } else if (exp > 0) {
// 1234e-2 -> 12.34[0+] // 1234e-2 -> 12.34[0+]
out = copy_str<Char>(digits, digits + full_exp, out); out = copy_str<Char>(digits, digits + exp, out);
if (!specs.showpoint) { if (!specs.showpoint) {
if (num_digits != full_exp) *out++ = decimal_point; if (num_digits != exp) *out++ = decimal_point;
return copy_str<Char>(digits + full_exp, digits + num_digits, out); return copy_str<Char>(digits + exp, digits + num_digits, out);
} }
*out++ = decimal_point; *out++ = decimal_point;
out = copy_str<Char>(digits + full_exp, digits + num_digits, out); out = copy_str<Char>(digits + exp, digits + num_digits, out);
// Add trailing zeros. // Add trailing zeros.
if (specs.precision > num_digits) if (specs.precision > num_digits)
out = std::fill_n(out, specs.precision - num_digits, zero); out = std::fill_n(out, specs.precision - num_digits, zero);
} else { } else {
// 1234e-6 -> 0.001234 // 1234e-6 -> 0.001234
*out++ = zero; *out++ = zero;
int num_zeros = -full_exp; int num_zeros = -exp;
if (num_digits == 0 && specs.precision >= 0 && specs.precision < num_zeros) if (num_digits == 0 && specs.precision >= 0 && specs.precision < num_zeros)
num_zeros = specs.precision; num_zeros = specs.precision;
if (num_zeros != 0 || num_digits != 0 || specs.showpoint) { if (num_zeros != 0 || num_digits != 0 || specs.showpoint) {