<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/87656>87656</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            fatal error: error in backend: Access past stack top!
        </td>
    </tr>

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

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

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

<pre>
    Compiling the following reduced program will result in clang crashing with the error in the title.

```
typedef long a;
namespace b {
namespace c {
namespace d {
namespace e {
namespace {
struct g {};
int h(g, bool, char *);
} // namespace
int i(double f, char *j) {
  a bits(f);
  bool k(bits);
  g l;
  return h(l, k, j);
}
} // namespace e
} // namespace d
} // namespace c
} // namespace b
```

I can compile the program with this command to see the crash:
`clang++ -mno-sse2 reduced-bug.cpp`

here's a godbolt reproduction:

https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:c%2B%2B,selection:(endColumn:17,endLineNumber:19,positionColumn:17,positionLineNumber:19,selectionStartColumn:17,selectionStartLineNumber:19,startColumn:17,startLineNumber:19),source:'typedef+long+a%3B%0Anamespace+b+%7B%0Anamespace+c+%7B%0Anamespace+d+%7B%0Anamespace+e+%7B%0Anamespace+%7B%0Astruct+g+%7B%7D%3B%0Aint+h(g,+bool,+char+*)%3B%0A%7D+//+namespace%0Aint+i(double+f,+char+*j)+%7B%0A++a+bits(f)%3B%0A++bool+k(bits)%3B%0A++g+l%3B%0A++return+h(l,+k,+j)%3B%0A%7D%0A%7D+//+namespace+e%0A%7D+//+namespace+d%0A%7D+//+namespace+c%0A%7D+//+namespace+b'),l:'5',n:'0',o:'C%2B%2B+source+%231',t:'0')),k:33.333333333333336,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:clang1810,filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1',verboseDemangling:'0'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:1,lang:c%2B%2B,libs:!(),options:'-mno-sse2',overrides:!(),selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:'5',n:'0',o:'+x86-64+clang+18.1.0+(Editor+%231)',t:'0')),header:(),k:33.333333333333336,l:'4',m:100,n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compilerName:'x86-64+clang+18.1.0',editorid:1,fontScale:14,fontUsePx:'0',j:1,wrap:'1'),l:'5',n:'0',o:'Output+of+x86-64+clang+18.1.0+(Compiler+%231)',t:'0')),j:__glMaximised,k:33.33333333333333,l:'4',n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4


I know I can avoid the crash if I put in a definition for `h` or enable sse2 instructions, I'm not looking for how to work around the crash, just reporting it so it can be fixed, as in my actual non-reduced program figuring out how to work around the crash is much less obvious.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJysV19vqzoS_zTOy6gRmPwhD3kodCud1e7pSkd7X48MHogbYyPbNO23v7KhBNKk7ZVOVTny_B975oeHWStqhbgn64ysHxascwdt9jlr_v1zUWj-ts910wopVA3ugFBpKfXJ7wzyrkQOrdG1YQ2chJRg0HbSgVBQSqZqKA2zBy99Eu4QDKAx2ngBv3HCSVyS6IFE98O6iYb_sHVvLXKsQGpVAyNJ1pMVa9C2rEQogGw_EMtrRH6NiNeII8k605UO6kDZPozuhXJwIDStCc2h0Fr63_LADBB6T-huFCTbByD0kdBHGM2fTQhCU667QiJUUwvPhO7OQQAwKISzhKbV1DYEz3AkNO3ZU1YNcrIz6DqjQsgh1KNfni8CvR0x4Cc8_gmv_IRXXL3vfv0BJVNQhsLDUCjnIgtlJKznNkxxcBos9kKh2EhyrqRQg4RmhGZw1yh9Zy3S98K9K7p6Wbbthe8DGiR0a4FBrXmhpQODrdG8K53Q6my-l3autZ4W0hsUltrUgZDUgRUTmoZqubXxQZea47-4cNoQmovATSsh0Z9Y2G1jQreE5pVW7lfJpKfGq4Hwf4v_e-3Fol7s2bMJzcMRJPcloWt_EGHJLUoc06EpKp5r2TV-G3tlVPw_QuHPrinQeOKO0LzVVnidueg79aP86OSXY8bNtea8K7pXVK5KBmHdmXI4pAEwCM08ZBCaMULXiU980uGEZkUoi_X2I6e8yeE3OXiTc6b2YEJoVk_I24dzeEJ57juu-Bh7ZPExHZgJWgFdRo3BQNZXH6HZxPNo8IwyhGbVpb2AAtMw-3Zh3v0EdCYuszGybIo9FxI-SXlJ7HFoSHJI7dj_PF9L7IsUM_xahH8tUn4tUoSe8rUm-zJb902mZi2n-10-bbVsKM6ekAw97KZ6QxUfSXKfJMtk9rc5u1x94rLfeCCKrljPr-NNQNcJ2oyU5D4AZ5zG3lolpEPTg1xazLwXQjHzNkOnnvRUPGPpZgyP16jck5JvMxsci67OmZR2Js6xYaqWOJcVxqPGC9oZGV-x7NwcJYVyKGdSUhSGmbdc87lRZ0QzU31BU2iLD30EQtWXx1lJVtu_BJ6eWlR_HJulKOzksrxD3XqoHJIeP2RDBbygMYLjpc5nEH8N4a8C_E18_wTev0D3j-B-HdsvoD3-dvsRmr2mm7vNyrf28ACI02W8jEITpu8f2bEhd7d78oCMh3DGY_1ml_qKiqPoD_ar7lzbuY_d-nN8H9zMOvRIyFrw4cD_YaGeDGunhf7Nq3gaYs509dWt5CMcfedefFy_f9fyv-xVNMIiv3UzfwI-J8nSL41cU35BY_tGXM1GneGte1T6BP2Tl71owc9vWRAV_IC2CwMVA46VUKEZodIGyCY6kE0E2gAq5qeI8LwVqn9pBMSgOfwgdNuA0g6k1kc_i3nlgz75p_NJmyMwozs1cRumg86Gh682zqsIB1b71UdZIFTiNRw6MOtja96Ala5jEpRWd5eTYSXqzngrunOfOgZhoenKA0i0FnTxInRnlwu-T_gu2bEF7uNtTOlqF0W7xWHPq2LDaYrxersqSlZUPIo3m2Sd7DbpLk3WC7GnEV1Fq2gVb1YJ3S63cZRskxgxZqxMNxVZRdgwIZdSvjT-2b4Q1na4T7eb9WYhWYHShsmYUoUnCExCqR-Uzd7r-CHCklUkhXX2bCXMtfuKOSb7gZck9-fJt2DlEZVvRbgvS59qy6wD61h5BKdbQuNFZ-T-YrgQ7tAVy1I3hD56T8PPXWt0-NrSxxCfJfQxxP93AAAA__9bPHoI">