| Issue |
98179
|
| Summary |
Clang emits the same debuginfo for `long double` and `__float128` on x86-64 and PowerPC despite them being different types
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
beetrees
|
On both non-Windows x86-64 (which uses `x86_fp80` as `long double`) and PowerPC (which uses `ppc_fp80` as `long double`), Clang emits `long double` and `__float128` with exactly the same debuginfo: a `DW_AT_encoding` of `DW_ATE_float` and a `DW_AT_byte_size` of `0x10`. This means debuggers like LLDB can't tell the difference: currently LLDB will presume the float type that is the same size as `long double` is `long double`, meaning `__float128` values get displayed as nonsense.
This can be seen by debugging this C program on an affected platform:
```c
void breakpoint(long double ld, __float128 f128) {}
int main() {
breakpoint(1.0, 2.0);
}
```
The `long double` will be displayed correctly in LLDB, whereas the `__float128` will not. This problem also affects debuginfo emitted by GCC and `rustc` (while `rustc` doesn't support `long double`, its `f128` type will still get misinterpreted as `long double` by the debugger).
While searching for previous discussion, I found [this thread](https://lists.dwarfstd.org/pipermail/dwarf-discuss/2022-January/002103.html) from January 2022 on the dwarf-discuss mailing list that appeared to be leaning towards adding new `DW_ATE` codes, but I haven't been able to find any further discussion since.
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