| Issue |
95361
|
| Summary |
Structure generated by clang-cl.exe on Windows is incompatible with MSVC ABI
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
adisak
|
I ran into an error in our codebase when mixing compilers. I have simplified the error to the reproducible example that follows.
The following code produces incompatible structures when compiled with MSVC vs clang-cl for Windows x64 target.
```
#include <iostream>
#include <xmmintrin.h>
typedef unsigned char u8;
struct __attribute__ ((ms_struct)) A
{
u8 u8_1;
int i_1;
__m128 vector_1;
protected:
bool b_1;
};
struct B : public A
{
void* pv_1;
};
struct C
{
__m128 vector_1;
};
static_assert(std::is_pod<C>(), "__m128 is NOT POD");
static_assert(!std::is_pod<A>(), "A is POD");
int main()
{
std::cout << "Size of A: " << sizeof(A) << "\n";
std::cout << "Size of B: " << sizeof(B) << "\n";
return 0;
}
```
The MSVC program has this output:
```
Size of A: 48
Size of B: 64
```
While the clang-cl program has the following output:
```
Size of A: 48
Size of B: 48
```
According to LLVM/clang documentation, clang-cl aims to be [ABI compatible with MSVC on Windows](https://clang.llvm.org/docs/MSVCCompatibility.html) but this doesn't appear to be the case. Is this a bug in clang-cl?
Is there a way to make clang-cl and MSVC generate the same layout for these structures?
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