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Fix num_get's float-parsing problem #3982

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Sep 7, 2023
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Fix num_get's float-parsing problem #3982

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4 changes: 0 additions & 4 deletions stl/inc/xlocnum
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Original file line number Diff line number Diff line change
Expand Up @@ -1019,10 +1019,6 @@ private:
_Seendigit = true;
}

if (_Seendigit) {
*_Ptr++ = '0'; // put one back
}

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for (size_t _Idx; _First != _Last && (_Idx = _STD _Find_elem(_Atoms, *_First)) < _Offset_dec_digit_end;
_Seendigit = true, (void) ++_First) {
if (_Exponent_part < PTRDIFF_MAX / 10
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21 changes: 21 additions & 0 deletions tests/std/tests/LWG2381_num_get_floating_point/test.cpp
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Expand Up @@ -532,6 +532,23 @@ void test_gh_3378() {
}
}

// Also test GH-3980 <iostream>: Wrong reading of float values
template <class Flt>
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Not worth resetting testing: vwls pls.
Flt isn't that much shorter than Float. If you want a descriptive name, be descriptive. If you want a short name, T would work fine here and honestly std::floating_point T (or static_assert(std::is_floating_point_v<T>) in the function body) would be even better.

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Float specifically is dangerous due to the potential confusion with float. Floating or any other name avoids that hazard.

void test_gh_3980() {
auto test_case = [](const char* str, double expected) {
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Not worth resetting testing: there are a log of strs floating around here, it might be nice to call this parameter "input" or something.

Flt val = 0;
istringstream{str} >> val;
assert((ostringstream{} << val).str() == (ostringstream{} << expected).str());
};

test_case("0x1p+07", 0x1p+07);
test_case("1e+07", 1e+07);
test_case("1e+0", 1);
test_case("1e-0", 1);
test_case("1e-07", 1e-07);
test_case("0x1p-07", 0x1p-07);
}

#if _HAS_CXX17
void test_float_from_char_cases() {
for (const auto& test_case : float_from_chars_test_cases) {
Expand Down Expand Up @@ -589,6 +606,10 @@ int main() {
test_gh_3378<double>();
test_gh_3378<long double>();

test_gh_3980<float>();
test_gh_3980<double>();
test_gh_3980<long double>();

#if _HAS_CXX17
test_float_from_char_cases();
test_double_from_char_cases<double>();
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