<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/124808>124808</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc][test] -Werror=maybe-uninitialized in high_precision_decimal_test.cpp
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            build-problem,
            libc
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            michaelrj-google
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          nickdesaulniers
      </td>
    </tr>
</table>

<pre>
    The unit tests fail with gcc-14:
```
In file included from /android0/llvm-project/libc/test/src/__support/high_precision_decimal_test.cpp:9:
In member function ‘bool __llvm_libc_20_0_0_git::internal::HighPrecisionDecimal::should_round_up(int32_t, __llvm_libc_20_0_0_git::internal::RoundDirection)’,
    inlined from ‘T __llvm_libc_20_0_0_git::internal::HighPrecisionDecimal::round_to_integer_type(__llvm_libc_20_0_0_git::internal::RoundDirection) [with T = long unsigned int]’ at /android0/llvm-project/libc/src/__support/high_precision_decimal.h:428:46,
    inlined from ‘virtual void LlvmLibcHighPrecisionDecimalTest_NumLenDigitsTest::Run()’ at /android0/llvm-project/libc/test/src/__support/high_precision_decimal_test.cpp:435:3:
/android0/llvm-project/libc/src/__support/high_precision_decimal.h:150:36: error: ‘longer_hpd’ may be used uninitialized [-Werror=maybe-uninitialized]
  150 |     if (this->digits[round_to_digit] == 5 &&
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~^
/android0/llvm-project/libc/test/src/__support/high_precision_decimal_test.cpp: In member function ‘virtual void LlvmLibcHighPrecisionDecimalTest_NumLenDigitsTest::Run()’:
/android0/llvm-project/libc/test/src/__support/high_precision_decimal_test.cpp:431:50: note: ‘longer_hpd’ declared here
  431 |   LIBC_NAMESPACE::internal::HighPrecisionDecimal longer_hpd =
      |                                                  ^~~~~~~~~~
```
In this case, I think GCC is correct.  The constructor for `HighPrecisionDecimal` doesn't guarantee that its `digits` member is fully initialized, so constructing an object then calling `round_to_integer_type` may end up reading uninitialized memory (UB).  I think the constructor of `HighPrecisionDecimal` should unconditionally initialize `digits`.
</pre>
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