<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/131107>131107</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            wcin >> buffer error
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

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

<pre>
    
sample

debug config 

launch.json
{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "type": "lldb",
            "request": "launch",
            "name": "Launch",
            "program": "${workspaceFolder}/build/testcpp",
            "args": [],
            "cwd": "${workspaceFolder}",
            "initCommands": [
                "settings set target.process.thread.step-avoid-regexp \"\"",
            ],
            "console": "integratedTerminal",
            "env": {
                "LANG":"en_US.UTF-8"
            }
        }
    ]
}

please add "LANG":"en_US.UTF-8"



<img width="714" alt="Image" src="https://github.com/user-attachments/assets/2870f4bd-9fe4-46d7-9b07-0ec0469efeb8" />

in file locale.cpp
codecvt<wchar_t, char, mbstate_t>::result codecvt<wchar_t, char, mbstate_t>::do_in(

have bug when trans utf-8 to wchar_t

when input 你123

do_in trans uncompleted utf-8 bytes with first byte 0xe4
and return ok, but correct is partial

so bug come out

</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJyUVVGP2zYM_jXKCxFDke1z8uAH36XZChR7aft8kCXaVitLnkQn7b8fZCe7tLvrNiCILerjx08UScsYTe8Qa1Y-svK4kTMNPtQa27lH3LRef68Zb6IcJ4uMN4w3yx4o7zrTw2qycnZqyL5E75KhemS8AQBg4sTECT5HhPeO0FrzEV1EIA8WZXAgWz8TTD5G01oESRRMOxPG7EeG3_0ZQ3I7G7yAxqiCmch4F8F3gN9MJOP6t_1PPsDoA4JxnQ-jTK5MPMHZREMsb2AgmiLLmxXf-2w0KvjoO8qUH5k4dRdr3Ne0nZ_Sm9EsP-5znu-rv0OJM4a4MIvEyYTgmch4WoqnF9SaujksKuINXN6StqCq-9XVj75P-EJtrW5_YL5DBvxzxkh34OWC3oI7Od4Rf_gldgq-D3J8gTNRsOrx4sPXOEmFJ281BlYdmTi1s7GaiRNhJDVNb1HK0N9noTy-ilIX_V-Cvh7COENPfhyl068n_A4bkVIxRYhIQDL0SNkUvMIYMxoCSp1Fwmkrz97obcAev03AyqfEu_6_KuKtY3kXvb1Lv3GEfZCE-hOG0Thp3zoUuvPN7R_lcoV8aP74bcUs-OfPH7PPn07bfbL9xFcdf6i_2yrpTi19XDt9sigjgtT63-lffvmTGXu4GE0Dy9MlVbuCCQHS0rp-P8o-5QBiUKvlp4Y0NMzttRXniGEriaQaRnQUmTjJGHF5EfuKd0Wrt4cOi23xoKvtoeXVlqPixcMBO2yTumUu5O9WecZBZyyC9UpazFKl8kZ5jepMLH-6qEGGZ0rjIr2l59hGkoTPlDjyhuVNwDhbgv_ppf2zcUzsVx2DPCOk2XoZ0AEF6SLM1G33afDd-BbkAjBumgnYu4I9HlnDdyK_zudEenN3yqfJTaivVO13wggXQwN0JkRaDMC_YcF4I52GgDQHB_5rktzO6UwhoCIwESYZyEi7xoke1g_BiODnpGyj61wf8oPcYL2rit2-rLioNkO9L9uHgyyLtlNthYe8exCIO7FXmj9I3fGNqQUXJc93OT_suHjIFJYlClXqfVVwme9YwXGUxmbWnsfMh35jYpyx3uW7Ha82VrZo4_IRE8LhBZbdpSOPm1Anp20795EV3JpI8YWGDFmsL8o4WK7lHbRz12EADMGHzRxs_YtSTDTXx3YK_gsqYuK0BE_VeFV3rsVfAQAA__84VCE4">