<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/86385>86385</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [X86_32] Structure of size 0 int c++ get wrong result when emit vaarg
        </td>
    </tr>

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

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

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

<pre>
    demo.c
```
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

struct S1644 {struct{int a[0];}b;} ;
struct S1644 s1644;
void check1644va (int z, ...) {
    struct S1644 arg;
    va_list ap;
 __builtin_va_start(ap, z);
    arg = __builtin_va_arg(ap, struct S1644);
    long double a = __builtin_va_arg(ap, long double);
 printf("%Lf\n", a);
    if (a != 2.0L)
 printf("Fail\n");
    __builtin_va_end(ap);
}
int main (void) {
    printf("%u\n", sizeof(s1644));
    check1644va (2, s1644, 2.0L);
}
```
clang:
```
0
0.000000
Fail
```
gcc:
```
0
2.000000
```
https://godbolt.org/z/G9enr4q5b
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyEVEFzszYQ_TXLRRNGrMDAgUNsl15ySw-9eSSQsRpZciXhTP3rO4LEsXG-fB4PQry37y27K7j3ajBSNlCsodgmfAwH65qN_UuZN-kSYfv_ml4ebdoB3QJ9hhX9-M9bZMp0euwlAbbxoddKpAdgf_wCVvYH1Ckz3MLT1Qc3doG8Zqs8J1Cu5z2Ua2UC4VCsKRRbYGsot2JeSFweY328XqGzVT3pDrJ7i4_PnABWUfECuCFpmgLW0W0mE0LInRZ3w1Upgme-08oHwk9fj3c7MSodlNmd-c4H7gJgxU9R_wJY38VzNxBg2_uYaPIZceu-DNbWDKS3o9CS8J9lbqh3KienTNgDVoAIWLzsodiY6X5D-NJP7WOxYsWyaIYpfYmUR6WWK30Vute4y1Ca_iPDLxKU2_kmNuXIlYmesWkPjVnkPt6k7tVF2gj5z7ot0lgMwBw0czfXF3tIaXEGOs3NAOz5W_BzSen0m3dTYb5jD133GyG8E1pwDiGcfBTAFrAdbC-sDqmNA9BeANs_a2lc_m8hkr5hfc1qnsgmK7Msq1YrViWHhsuM8lwIsed9ximu6horKbAUspaVqBPVIMWcMmS0ZmVWpaXYlxJpL-qc9Z0sIafyyJVOtT4fo3eivB9lU61YVSSaC6n99LVBNPKdTGBsV7FNXBNjnsQ4eMhpPFD-SyWooKfP1N_Vascin7xOh2J0ktj91GtCSRyXDnANuCaDDOTdxZF30o86kPeDNEQeVSBnzt2QjE43i5qpcBhF2tkjYBu9P5ank7P_yC4AtlPGHrCd3uj_AAAA__-khXQF">