<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/67380>67380</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang-tidy] "unknown pragma ignored" generated on "pragma pack" in c++20 mode
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang-tidy
      </td>
    </tr>

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

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

<pre>
    Source `test.cpp`
```cpp
#pragma pack(1)
struct S {};
```
Compiling with `clang++-17 -Wall -Werror -std=c++20 -o test.o -c test.cpp` works fine, no errors.

I created `/tmp/test/compile_commands.json` using `-MJ` clang option
```json
[
  {
    "directory": "/tmp/test",
 "file": "test.cpp",
    "output": "test.o",
 "arguments": [
      "/usr/lib/llvm-17/bin/clang",
 "-xc++",
      "test.cpp",
      "-o",
      "test.o",
 "--driver-mode=g++",
      "-Wall",
      "-Werror",
 "-std=c++20",
      "-c",
 "--target=x86_64-pc-linux-gnu"
    ]
  }
]
```
Running `clang-tidy-17 test.cpp` in /tmp/test folder produces following output
```console
$ clang-tidy-17 test.cpp
1 error generated.
Error while processing /tmp/test/test.cpp.
test.cpp:1:9: error: unknown pragma ignored [clang-diagnostic-unknown-pragmas]
    1 | #pragma pack(1)
      |         ^
Found compiler error(s).
```

I am using latest 17 build from LLVM apt repo
```console
$ clang++-17 --version
Ubuntu clang version 17.0.2 (++20230925113614+481358974fb0-1~exp1~20230925113629.44)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ clang-tidy-17 --version
Ubuntu LLVM version 17.0.2
  Optimized build.
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyMVU2P2zYQ_TX0ZSBBGn1ZBx_sVQy0SFCgaZtjQEmUzIQiBZLa3fSQ316Qotder7OoYQgSZzh8M_PmkRrDR8nYjhQHUjQbutiT0rtHzqTdtKr_sfusFt0xIGVimbFxN8-kTEjSkGTvXvzfLa4rmM2ajhOFmXbfCW5TgvVqMlYvnYXPQKoDqRqSHW6CrJ8Papq54HKEJ25P7thOUDkSPBA8RGkF0RcqBERfmNZKQ2RsT7KmW-2YQKTA41QQdXCFGJ6U_m5g4JIRfACpwAcwcUDhn79Bpxm1rHfnEjzaaXZPZizBY-eRsa-dmiYqexN_M0q6yItxcEmZRJ9-d98eMKjZciVvcvRb1qUi5A--IOEVgCD2XLPOKv2DIJJs75ZusCDBh7CFIA5csIvrS87XXmtgtdh5sTeu6jYc1eMyMWnN2bG4ggcBzWI0waPgrXuKxylKK4LHlktXqLVhr6NGz6FHt7jgPdDeGKlf73mDPop6zR-ZjibVM5I14zuneir9wuLZ8Sb4Ddvu7-3eYrJUj8ySrHnell_LPJq7SHC5PEejXJz3pUtFc6FFc6ZKc3dU_lykDMzzJY8s73-4EbmmPZfwijwwKNEzDbNW_dIx476FenJxAj1uRltJowQ7j3cOvzjK29N1qGBkkmk3R2G6PvjVpxMXzB3cMbOOzM2EnYOFXS-xs31Ksn3tyLi2JdvDIr9L9SQhyA0fpdJubovDCrDndJTKWN5FwTVaXc1ViQFSINUDvCNboa3VA5x_pPiwmo5qkT0EWdABGm4NwTq-27CzyNApaIagviVpBe3CRQ-DVhN8_PjPJ6CzBc1m9b-6cSWO0SPT5kV3_m4XaZcgSMECaRUnMQLB7ZnGmCU1FmmalWlO8JBv06zY1lU-tEmU_mTPc_rz2gnrOM9fCvRXoPYe7nF7dTlpRntwEymc46wMfw7FkMZSIVjfcL2qUpAWJyVXRXvLvPup-uK9zvTcxz9myyf-L-vXYt-2aNPvsr7Oarphu7Ssi3KLiNXmtBuqNKdl37GcDmldVAOjyLo26XuKdTsUG747VwexSLCK0yrFrE27Mh-GqhhSkidsolzETiljpccNN2Zhu7LKtslG0JYJ4y9gxEuOThaKZqN3Xl7bZTQkTwQ31lzCWG6Fv7qvthWNk5z740EQL7MJykkDviI-Or24XKauY5tFi93J2tmQbE_wSPA4cnta2rhTU1D_8yUwa_WNdW6UfYKG4NHn-F8AAAD__9DIYmI">