phyBrackets wrote:
> > However, GCC also tends to only emit debug info for static members when
> > they're ODR-used and get storage,
>
> Can we do that? (or do we already do that and this patch is about explicitly
> doing something different?)
>
> > Given that's a Clang-specific concern, I'm still happy to add a size cap if
> > we think it's warranted. Or any other idea or path we need to look for?
>
> Not sure - cap doesn't really inspire me & probably isn't worth a flag right
> now. It's probably just going to be a matter of trying it in the wild and
> seeing what breaks. Though I don't feel great about it (mostly don't feel
> great about emitting debug info for things that aren't concretely in the
> output binary - but I know that's at odds with constexpr stuff which is still
> important for debugger users but doesn't have presence in the binary)
Hi @dwblaikie , I tested this locally to be sure, turns out GCC actually does
emit all three member DIEs (scalar, arr, f) inside the type unconditionally,
even when nothing is ODR-used. And it attaches `DW_AT_const_value` to the array
with the raw bytes, no size cap:
```
struct Foo {
static constexpr int scalar = 42;
static constexpr int arr[] = {1, 2, 3};
static constexpr float f = 3.14f;
};
// Nothing ODR-used
Foo foo; int main() { return 0; }
```
GCC:
scalar: DW_AT_const_value (0x2a)
arr: DW_AT_const_value (<0x0c> 01 00 00 00 02 00 00 00 03 00 00 00)
f: DW_AT_const_value (<0x04> c3 f5 48 40)
Clang (trunk, without this patch):
scalar: DW_AT_const_value (42)
arr: (declaration only, no const_value)
f: DW_AT_const_value (1078523331
So GCC's been doing exactly this for a while with no complaints. Clang already
emits the arr declaration. Limiting to ODR-used only would be a separate
broader change affecting all static constexpr members, including the scalars
that already have const_value today.
https://github.com/llvm/llvm-project/pull/182442
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