eisenwave wrote:
Well, I'm not sure if it's a good sign or a bad sign, but this warning gives us
a *whole bunch* of diagnostics in libc:
```
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/src/__support/CPP/bit.h:55:10:
error: '__builtin_bit_cast' from 'const long double' to 'unsigned __int128' is
always undefined because it unconditionally maps a padding bit onto a
non-padding bit [-Werror,-Wbit-cast-padding]
55 | return __builtin_bit_cast(To, from);
| ^
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/src/__support/FPUtil/FPBits.h:842:21:
note: in instantiation of function template specialization
'__llvm_libc_23_0_0_git::cpp::bit_cast<unsigned __int128, long double>'
requested here
842 | UP::bits = cpp::bit_cast<StorageType>(x);
| ^
/home/gha/actions-runner/_work/llvm-project/llvm-project/libc/src/__support/FPUtil/generic/sqrt_80_bit_long_double.h:46:10:
note: in instantiation of function template specialization
'__llvm_libc_23_0_0_git::fputil::FPBits<long double>::FPBits<long double, 0>'
requested here
46 | LDBits bits(x);
| ^
```
I guess this means
- There is a good chance that this warning will be very noisy for code bases
that make heavy use of `std::bit_cast` to convert `long double`
- Maybe that's a good thing because all of that is latent undefined behavior
anyway
https://github.com/llvm/llvm-project/pull/200362
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