<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/71250>71250</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] Assertion in `getObjCEncodingForStructureImpl` with `[[no_unique_address]]` in Objective-C++ class
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++20,
            clang:codegen,
            crash-on-valid,
            objective-c++
      </td>
    </tr>

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

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

<pre>
    When compiling the following Objective-C++ code with an asserts build of `main` (c7a7a43db):

```objc++
struct Empty {};
struct Foo {
 [[no_unique_address]] Empty m_empty;
  long m_a;
  long m_b;
};
@interface Bar {
  Foo m_foo;
}
@end
@implementation Bar
@end
```

The following assertion below is triggered:

```
void clang::ASTContext::getObjCEncodingForStructureImpl(clang::RecordDecl*, std::string&, const clang::FieldDecl*, bool, clang::QualType*) const: Assertion `CurOffs <= CurLayObj->first' failed.
```

<details>
<summary>Complete backtrace</summary>

```console
clang++: /root/llvm-project/clang/lib/AST/ASTContext.cpp:8598: void clang::ASTContext::getObjCEncodingForStructureImpl(clang::RecordDecl*, std::string&, const clang::FieldDecl*, bool, clang::QualType*) const: Assertion `CurOffs <= CurLayObj->first' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -x objective-c++ <source>
1.      <eof> parser at end of file
2.      <source>:11:17: LLVM IR generation of declaration 'Bar'
 #0 0x0000000003778cf8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3778cf8)
 #1 0x00000000037769bc llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x37769bc)
 #2 0x00000000036bf368 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x00007f7dbf9ec420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007f7dbf4af00b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #5 0x00007f7dbf48e859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #6 0x00007f7dbf48e729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #7 0x00007f7dbf49ffd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x0000000006de73e7 clang::ASTContext::getObjCEncodingForStructureImpl(clang::RecordDecl*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&, clang::FieldDecl const*, bool, clang::QualType*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6de73e7)
 #9 0x0000000006de807e clang::ASTContext::getObjCEncodingForTypeImpl(clang::QualType, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>&, clang::ASTContext::ObjCEncOptions, clang::FieldDecl const*, clang::QualType*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x6de807e)
#10 0x0000000003f2cb91 (anonymous namespace)::CGObjCGNU::GenerateClass(clang::ObjCImplementationDecl const*) CGObjCGNU.cpp:0:0
#11 0x0000000003b72f40 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#12 0x00000000049eb916 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#13 0x00000000049dc9d8 clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49dc9d8)
#14 0x0000000005efdd54 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x5efdd54)
#15 0x00000000049e9208 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x49e9208)
#16 0x000000000424bdc9 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x424bdc9)
#17 0x00000000041cc4be clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x41cc4be)
#18 0x000000000432afce clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x432afce)
#19 0x0000000000bf5fd6 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbf5fd6)
#20 0x0000000000bed89a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#21 0x0000000004027cc9 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#22 0x00000000036bf814 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x36bf814)
#23 0x00000000040282bf clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#24 0x0000000003ff0215 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff0215)
#25 0x0000000003ff0c7d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff0c7d)
#26 0x0000000003ff8ba5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0x3ff8ba5)
#27 0x0000000000bf347c clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbf347c)
#28 0x0000000000aec0b1 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xaec0b1)
#29 0x00007f7dbf490083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#30 0x0000000000bed37e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+++0xbed37e)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
```

</details>

 Removing the two `long` member variables or moving the `[[no_unique_address]]` member from the C++ class to the ObjC class leads to successful compilation.



Godbolt link: https://godbolt.org/z/G35PvPP8j
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkWl1z4yrS_jXkhlJKRrI-LnLhOPG8c2rOm-wke_bShQA5zCDQAso4--u3ANkWjpOTOZXMXpypiRMh1P300013I4yN4RvJ2AWYX4L51Rke7IPSF5dMWyywvDprFH26-NcDk5CorueCyw20Dwy2Sgj1w13dNN8YsfyRJUuALgG6hERRBn9w-wCxhNgYpq2BzcAFhaqFoEg7zCUoUghQRUpc4jyjDUA1yBYgvQLp7rNIw3_VfCNBdLhhrB6Ihdddb58gKC9BeQWy-N5KKX_Hj0Fv3KVU60Hyfw9sjSnVzBgwvwLzq1FOt2bu914QhELJDezW-PlQsx-aqgZ5yqVlusWEwUusJwA8nm7dKhU9uXuMSXoQ0fWCdUxabLmSTs6JaTtmpnTdR14JtDsJDRPqB-QGWs03G6YZfYnncPmoOIVEYLlx87LF4u5-qaRlWxuuN8zeNN-W15IoyuVmpfSd53zQ7HPXC-fTw8NfGVGaXjEiAFoAtITG0nDHWM3lBqDCjRIljZ0qXXEmpo81Sgk_8TDlHwMW90898zPqIAJkC7jYWw6KdDnom7Y1EGRLkF3B5aC_4Keb5lsCsuuWa2MBKmGLuWD0_BVuQbakzGIuDMiu90Nm6Dqsn0B2vVTOa5bBBpPvVmPCnEK0Osw4SbjDrAQLo8G0EObZAgK00kpZgFZCPHZJr5VbZgCtxnkrwRuAVou7-_A5-uic9D3IFtW8rpyUv7kzb79cL-6uoRmajluIYTNsoGa90hZaBR-s7Y3Tj1YArTbcPgzNOVHdyPlz6rkxAzMArSCWFHJJxECZT4dEY_Mw8T5awl6zXivCjGEUGjXoMOyexMYowrFlFOpBQkM07-0I-c5i8h3Soev3yzQ9B2l9q9VG4w5ivRlcejBjkKjeB4VPzkwnbNsLpZneBUqyTwQmsXqQ3wFaNVwe4shn7GRDf2DdJjlMNjBRTi7ueyd9sP1gzw1MOscFTJJtVSTYdIl5khZvQXblcp6AyR1Mkg0hiVVKkAeX4LOrV-G5yUbi3jwoC5OWKKF0QjneSGUsJwYmrVSJJzYe3kK1LzljXXAhMVK8W2ozRxrIlky1ILuGPdaGaYgtZNKXoZbvFh4aZx4EZIvZzH2UjuMvX_74HX7-CjdMMh2SsmohZUTg8RKg0qVpVO7KDcpSmG7T3b-sLCvSVtAHVVgvTyb8cau5tN7l9yFuqsMkjX-slbGa4W5cWVxatzoAqt7J8QBdptsRnivAe_yzI_xF3ZBT-JeCYTn0N_KObyR2-WKQvqOgvlZ-DFoHJkKLIrRF02ZFBZcuclzKemT6KcD7PyypcEqrkcloTpxBU_-zV5GNKsq2pE1bM5KjFK7XmhmrNFtrO9oZsvK2KtZFngguh22ykUO40dsHzTA9N-o89bbM8hylkSV5pCbHbZo2UGNu2BvkEye58JLzLE2bSPI8llyxal5D3Kg3IZ9IRqia15Hk4lhyuff6m2WWKJZZxjLrtqXFz8nMspYWkcxqGiUFZWXGyl9QG9drst36fAKyRYMNJ-uxXGZL8uDyxmSyG1hbjbnL7-F2dh3NwEIogq3Sk_tuSnFUUfdFdyymP1V633vRjmxH7qiP3FGlJfs5dzjUzz1xsOd_74RjG0YDbnpP2ps89us95Ryx95SrBXExaxFp6pnTi6WST50aDJS4Y6b3BaweC8MnZ-un__9nuPwUiidbCmxM7C8373O06TnioIZ7Yc9zs8MXF6umRG2eTnlbKso-MRld_K7oIFgYuu64vVf9F_bIRFjBU3z7Ne2T2nmPtXXpu4aRpNPIosKU16ypZ8WfMhfEOrqU9uHth0Pteh3mJ62G_itrHboA69Ltupk-jS6L0VFS02rK2yUm35mkSyXN0DH913C8c3yOMKP4zKd2zFlL6Tyf2nHrej-_UZoCvWMdHlfsLiuG3--OeYQUYZ4fRUaN0upEzC6IUzCG6ZaRwbJxyEH8AHY9kAhpESFFeUNJHaUt7TKcpCegfhDIgCECWUYgZ4TkDYvpDGo_S2OxJOw0oy9b5eLk_Q0JOCNDoiYlzxBuSWTICPlgz6MrRM_gP7N3n8De1YCALzIgKutp085d50bIbO1f-k33Nwut8ZPLEqGGHjJ-KLbxGFr6dxkfY0dAOTUDpbEZjFY1hjvyl7N7nykmxtx1WIg_GNnn7BM2-VxzeMTJGLuD3TwfZVTzxxdSNopKXZ6ikpA6vOQ5yG0H6YN2rT23_m5YiWFv6zocLESDyfd1Kx3SQ9wE3WMMLWdL1XVY0uNFfdKH--ZI-e4GOw4m_Phuy8-8Pu6mflFzNmmAo5dM_g1QKXDXUOw28XuqULXbw_6mmtP-eLbzrGb5xBWn9pfjfmGQd7hl4imi83XXfcBmOiCOIj87CrEKNS38O4fIUdv3YizkcZvcpmg2f5E47zv8rGLu2IyS-dGDbsIkYSxf0TGduoianQ_aPoxmRwE1P-aFlPRneflNNeZlUn5TzRdubETKa6l5Hwc95i4E_Nugt_M43ex9OJukpBGbxRGbVYNfjLKryd9R43CiY3jJC7-QzfdPb4GeiL_yqD_J8pIErLsOZYffp5XFmBT-vGy_e0_ikEXQo94wxYykzQw60O-tO4iOdNdHL-TStMrgei144zIx1nY9AfLW1355WmVTLdmzrisrGQzy351fL3yv_ej0jWntisMiRAZsx90AJGP0hlOmcMjNttyGM-9ZljuYg2EweYRWQcMY5JMWvX79jBGg1bNjxvC-7Cvr1OPu7N3-UBAUqW9OihR2rGuYho9Yc9wIZqDScDLbqXnt_HsiotWq88_sT_IFNsYZ4gZvmm_LcUQwTP24GQhhxrSDGL8f4A09j-yafH5StFHCQsHld8fu0QlcuHuu9Aag1X8AWn3K5rePt7fVtzN6kdE6q_EZu5gVdZ3Os6yqzx4uWImLNJuxbIZmedvUDZqhNkcppShLCSvO-AVKUTabpZnby6L6nNB2NsvSvMFNShkpQZ6yDnNx7pa4033mj_kuyhmap2cCN0wY__UIhMbTJpQChABaupExyTn3b5g8jPtjKyWTRyzcrmUcfnZw5e7Mr870hT9pbIaNAXkquLHmAMdyK_wXNIKy-dXkVJT7g9E_e1NdpCFS3xIKXJ76Rofz-tmgxcVfPzP1fP43AAD__-QKg04">