<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylVtty4jgQ_Rrz0gUFNtcHHgiQytQmk9SEqdQ-UUJu29rIkkuSw_D30xLmkgVm9uIyxpbV0jl9TjdsdLqbcslU3uYShFVRPHJgnRHcASpd5wVshStAafzBsXIdmGtlRYomSmZRdxF1m-uHFilkUTyO4slxdpTcXXkL0eguGi3Oo_dXLjv4A6Fk72jBFcICU4DGaAMUyiykml4EuCAU7aLaB-ztUqdIi_8NVZTMra4NxyhZ0hLxfkaz5jxOaIQeiTRhG_lbgylmQgkntCL0kIosQ4OKshEY0TDYCrnIBGf-yV7dqNdspLRD_20RIUUCa0IQ6Oy46UUWvjgatqCV3AGDLTNK7PkeuP6KYzLzjIZ-zybyjCAJDKWw1q93g46felSPIqLBXfutFNxoqzPXPka1fVQ0WPxOXvBHNFiePfnjuMUZj5kjzREsKxGcKEnNOZxZE5zWB2cGS67XPqMBRzymRBdGby8dcGMWBMj5HvJnmzaDV1za-DO48OvziszB8sanDpiUnc-TG-heB_trzQbXNcv_uWbrNXOUm03tcL0OBM5T4s9_peW1HNyQ8rc7XyPc90YdnldIZfBD6Np-KhPiXlD1_Qcl4dZxJHBVK1voWqZBXC9F2B2Q3Iam43vQTFrtfSkc1DY0KYSt0aQN4ZLSi0Sl7UePSfGV6we8WXwojYHIYOt9tG-3wUZ7B9FMti9_FtobCV8jZNSsgs0qZpzgNeUHwpvOKb8X15UPKAkGGgsb5IwAByCviz-Aa-WYuLRlnIT2R5NWi6fl6uF5QaRLdIVOQ6qFcTWTMH9-Wi-W88fXl-V8Tcl6-Pb8Bg_flq_fH1en0Pns8XH158sSmgUuIL7qwPl8L9qFuJtDt8T0Zpk3qTwwCu3SV-aVfFyy-vL0cm6Km9CvYg5qYsZq6U4R5I77z-tXIffUtlmwyqmVh-51ag_-iYKtS0kNInlHZ28U7BY0DO2GiEPBqgpVCNDEnJ2iIJMsvzBDPOa6EpTC4B39gQYyo8uAn1MaS1GXlENqYYbxd_pFp5RqI3KhSJUdZEJS7GYHUb-rBCffT1rpNEknyYS1WE0gzJSVu_eiJiat2shp4VwVLBXf05kTznrT4bqkByk_Dl_tyui_kJPN74OJLd0M4vGw2yqmY-zz8WiT9iaDfpdPhtm4P-qzlAb6k36fbVqSbVDaKbWyKI4Vbvd1QPfUv1r_H4GYxt2414vjJKbPYNhJ02GajEcJy3pdxgc9ygWWTMiOX6ejTd4y07Ak5dHSSymss6eXjBp3rhAbwMd0NYCdcBJP_79O_d23BKUtFbs9tgmqZe59E36DbrimFfhMA5mfbT4Djw>52860</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang-cl exception diagnostics don't match cl.exe with /std:c++17
        </td>
    </tr>

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

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

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

<pre>
    clang-cl isn't strict enough with noexcept. Consider:

void f() noexcept;
void f()  {}


cl.exe makes this an error (as does clang in non-clang-cl-mode):

<source>(2): error C2382: 'f': redefinition; different exception specifications
<source>(1): note: see declaration of 'f'


It's only a warning in clang-cl:

<source>:2:6: warning: 'f' is missing exception specification 'noexcept' [-Wmicrosoft-exception-spec]
void f()  {}
     ^
         noexcept

At the same time, clang-cl is too strict with __declspec(nothrow):

__declspec(nothrow) void g();
void g() {}

cl.exe does NOT diag this at all.

clang-cl warns:

<source>:5:6: warning: 'g' is missing exception specification '__attribute__((nothrow))' [-Wmicrosoft-exception-spec]
void g() {}
     ^
         __attribute__((nothrow))
<source>:4:26: note: previous declaration is here
__declspec(nothrow) void g();
                         ^


clang-cl should NOT warn here either. (Also, it uses the wrong spelling of the attribute in the diag, but if we don't diag at all that's a non-issue for this particular issue.)



This matters because the SDK contains:

#define STDMETHOD(method) virtual COM_DECLSPEC_NOTHROW HRESULT STDMETHODCALLTYPE method


So all STDMETHOD()s are declared __declspec(nothrow), but the SDK only does


#define STDMETHODIMP            HRESULT STDMETHODCALLTYPE


So the default STDMETHOD / STDMETHODIMP pattern causes a warning with clang-cl with /std:c++17. (This does not happen without a /std: flag.)

(copied this over from the chromium bug tracker, originally filed by @nico)
</pre>
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