Name the captured upvars for closures/generators in debuginfo
Previously, debuggers print closures as something like
```
y::main::closure-0 (0x7fffffffdd34)
```
The pointer actually references to an upvar. It is not very obvious, especially for beginners.
It's because upvars don't have names before, as they are packed into a tuple. This PR names the upvars, so we can expect to see something like
```
y::main::closure-0 {_captured_ref__b: 0x[...]}
```
r? `@tmandry`
Discussed at https://github.com/rust-lang/rust/pull/84752#issuecomment-831639489 .
[debuginfo] Emit associated type bindings in trait object type names.
This PR updates debuginfo type name generation for trait objects to include associated type bindings and auto trait bounds -- so that, for example, the debuginfo type name of `&dyn Iterator<Item=Foo>` and `&dyn Iterator<Item=Bar>` don't both map to just `&dyn Iterator` anymore.
The following table shows examples of debuginfo type names before and after the PR:
| type | before | after |
|------|---------|-------|
| `&dyn Iterator<Item=u32>>` | `&dyn Iterator` | `&dyn Iterator<Item=u32>` |
| `&(dyn Iterator<Item=u32>> + Sync)` | `&dyn Iterator` | `&(dyn Iterator<Item=u32> + Sync)` |
| `&(dyn SomeTrait<bool, i8, Bar=u32>> + Send)` | `&dyn SomeTrait<bool, i8>` | `&(dyn SomeTrait<bool, i8, Bar=u32>> + Send)` |
For targets that need C++-like type names, we use `assoc$<Item,u32>` instead of `Item=u32`:
| type | before | after |
|------|---------|-------|
| `&dyn Iterator<Item=u32>>` | `ref$<dyn$<Iterator> >` | `ref$<dyn$<Iterator<assoc$<Item,u32> > > >` |
| `&(dyn Iterator<Item=u32>> + Sync)` | `ref$<dyn$<Iterator> >` | `ref$<dyn$<Iterator<assoc$<Item,u32> >,Sync> >` |
| `&(dyn SomeTrait<bool, i8, Bar=u32>> + Send)` | `ref$<dyn$<SomeTrait<bool, i8> > >` | `ref$<dyn$<SomeTrait<bool,i8,assoc$<Bar,u32> > >,Send> >` |
The PR also adds self-profiling measurements for debuginfo type name generation (re. https://github.com/rust-lang/rust/issues/86431). It looks like the compiler spends up to 0.5% of its time in that task, so the potential for optimizing it via caching seems limited.
However, the perf run also shows [the biggest regression](https://perf.rust-lang.org/detailed-query.html?commit=585e91c718b0b2c5319e1fffd0ff1e62aaf7ccc2&base_commit=b9197978a90be6f7570741eabe2da175fec75375&benchmark=tokio-webpush-simple-debug&run_name=incr-unchanged) in a test case that does not even invoke the code in question. This suggests that the length of the names we generate here can affect performance by influencing how much data the linker has to copy around.
Fixes https://github.com/rust-lang/rust/issues/86134.
- Closures in external crates may get compiled in because of
monomorphization. We should store names of captured variables
in `optimized_mir`, so that they are written into the metadata
file and we can use them to generate debuginfo.
- If there are breakpoints inside closures, the names of captured
variables stored in `optimized_mir` can be used to print them.
Now the name is more precise when disjoint fields are captured.
Previously, debuggers print closures as something like
```
y::main::closure-0 (0x7fffffffdd34)
```
The pointer actually references to an upvar. It is not
very obvious, especially for beginners.
It's because upvars don't have names before, as they
are packed into a tuple. This commit names the upvars,
so we can expect to see something like
```
y::main::closure-0 {_captured_ref__b: 0x[...]}
```
Support pretty printing slices using GDB
Support pretty printing `&[T]`, `&mut [T]` and `&mut str` types using GDB.
Support pretty printing `&mut [T]` and `&mut str` types using LLDB.
Fixes#85219.
Previously, only the fields would be displayed with no indication of the
variant name. If you already knew the enum was univariant, this was ok
but if the enum was univariant because of layout, for example, a
`Result<T, !>` then it could be very confusing which variant was the
active one.
Previously, directly tagged enums had a `variant$` field which would
show the name of the active variant. We now show the variant using a
`[variant]` synthetic item just like we do for niche-layout enums.
Also an fix issue with tuple type names where we can't cast to them in
natvis (required by the visualizer for `HashMap`) because of
peculiarities with the natvis expression evaluator.
There are several cases where names of types and functions in the debug info are either ambiguous, or not helpful, such as including ambiguous placeholders (e.g., `{{impl}}`, `{{closure}}` or `dyn _'`) or dropping qualifications (e.g., for dynamic types).
Instead, each debug symbol name should be unique and useful:
* Include disambiguators for anonymous `DefPathDataName` (closures and generators), and unify their formatting when used as a path-qualifier vs item being qualified.
* Qualify the principal trait for dynamic types.
* If there is no principal trait for a dynamic type, emit all other traits instead.
* Respect the `qualified` argument when emitting ref and pointer types.
* For implementations, emit the disambiguator.
* Print const generics when emitting generic parameters or arguments.
Additionally, when targeting MSVC, its debugger treats many command arguments as C++ expressions, even when the argument is defined to be a symbol name. As such names in the debug info need to be more C++-like to be parsed correctly:
* Avoid characters with special meaning (`#`, `[`, `"`, `+`).
* Never start a name with `<` or `{` as this is treated as an operator.
* `>>` is always treated as a right-shift, even when parsing generic arguments (so add a space to avoid this).
* Emit function declarations using C/C++ style syntax (e.g., leading return type).
* Emit arrays as a synthetic `array$<type, size>` type.
* Include a `$` in all synthetic types as this is a legal character for C++, but not Rust (thus we avoid collisions with user types).
- Literally, variants are not artificial. We have `yield` statements,
upvars and inner variables in the source code.
- Functionally, we don't want debuggers to suppress the variants. It
contains the state of the generator, which is useful when debugging.
So they shouldn't be marked artificial.
- Debuggers may use artificial flags to find the active variant. In
this case, marking variants artificial will make debuggers not work
properly.
Fixes#79009.
All fields except the discriminant (including `outer_fields`)
should be put into structures inside the variant part, which gives
an equivalent layout but offers us much better integration with
debuggers.
As mentioned in #79009, there are four failed debuginfo test cases
when using GDB 10. This commit fixes two of them, which fail because
GDB 10 won't print pointers as string anymore. We can use `printf`
as a workaround. It should work regardless of the version of GDB.
Refer this [comment] for more details.
[comment]: https://github.com/rust-lang/rust/issues/79009#issuecomment-826952708
Stablize `non-ascii-idents`
This is the stablization PR for RFC 2457. Currently this is waiting on fcp in [tracking issue](https://github.com/rust-lang/rust/issues/55467).
r? `@Manishearth`
The issue was that the resulting debuginfo was too complex for LLVM to
translate into CodeView records correctly. As a result, it simply
ignored the debuginfo which meant Windows debuggers could not display
any closed over variables when stepping inside a closure.
This fixes that by spilling additional variables to the stack so that
the resulting debuginfo is simple (just `*my_variable.dbg.spill`) and
LLVM can generate the correct CV records.
