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Prevent overflow with zero precision

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This commit is contained in:
Victor Zverovich 2019-03-13 10:46:25 -07:00
parent 49bbf3c876
commit e28429ee73
2 changed files with 12 additions and 6 deletions
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17
include/fmt/format-inl.h
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@ -489,8 +489,9 @@ digits::result grisu2_gen_digits(fp value, uint64_t error, int& exp,
// The fractional part of scaled value (p2 in Grisu) c = value % one. // The fractional part of scaled value (p2 in Grisu) c = value % one.
uint64_t fractional = value.f & (one.f - 1); uint64_t fractional = value.f & (one.f - 1);
exp = count_digits(integral); // kappa in Grisu. exp = count_digits(integral); // kappa in Grisu.
auto result = handler.on_start(data::POWERS_OF_10_64[exp] << -one.e, value.f, // Divide by 10 to prevent overflow.
error, exp); auto result = handler.on_start(data::POWERS_OF_10_64[exp - 1] << -one.e,
value.f / 10, error * 10, exp);
if (result != digits::more) return result; if (result != digits::more) return result;
// Generate digits for the integral part. This can produce up to 10 digits. // Generate digits for the integral part. This can produce up to 10 digits.
do { do {
@ -571,18 +572,22 @@ struct fixed_handler {
bool fixed; bool fixed;
bool enough_precision(int full_exp) const { bool enough_precision(int full_exp) const {
return full_exp <= 0 && -full_exp >= precision; return /*full_exp <= 0 &&*/ -full_exp >= precision;
} }
digits::result on_start(uint64_t divisor, uint64_t remainder, uint64_t error, digits::result on_start(uint64_t divisor, uint64_t remainder, uint64_t error,
int& exp) { int& exp) {
// Non-fixed formats require at least one digit and no precision adjustment.
if (!fixed) return digits::more; if (!fixed) return digits::more;
int full_exp = exp + exp10; int full_exp = exp + exp10;
if (full_exp >= 0) precision += full_exp; // Increase precision by the number of integer digits, e.g.
// format("{:.2f}", 1.23) should produce "1.23", not "1.2".
if (full_exp > 0) precision += full_exp;
if (!enough_precision(full_exp)) return digits::more; if (!enough_precision(full_exp)) return digits::more;
auto dir = get_round_direction(divisor, remainder, error); auto dir = get_round_direction(divisor, remainder, error);
if (dir == up) buf[size++] = '1'; if (dir == unknown) return digits::error;
return dir != unknown ? digits::done : digits::error; buf[size++] = dir == up ? '1' : '0';
return digits::done;
} }
// TODO: test // TODO: test

1
test/format-test.cc
View File

@ -1471,6 +1471,7 @@ TEST(FormatterTest, FormatDouble) {
} }
TEST(FormatterTest, PrecisionRounding) { TEST(FormatterTest, PrecisionRounding) {
EXPECT_EQ("0", format("{:.0f}", 0.1));
EXPECT_EQ("0.000", format("{:.3f}", 0.00049)); EXPECT_EQ("0.000", format("{:.3f}", 0.00049));
EXPECT_EQ("0.001", format("{:.3f}", 0.0005)); EXPECT_EQ("0.001", format("{:.3f}", 0.0005));
} }