Better attribute and metaitem encapsulation throughout the compiler
This PR refactors most (hopefully all?) of the `MetaItem` interactions outside of `libsyntax` (and a few inside) to interact with MetaItems through the provided traits instead of directly creating / destruct / matching against them. This is a necessary first step to eventually converting `MetaItem`s to internally use `TokenStream` representations (which will make `MetaItem` interactions much nicer for macro writers once the new macro system is in place).
r? @nrc
book/ffi: nullable pointer cleanup
Expand the "nullable pointer optimization" section with a code example. Fixes#34250.
I also noticed that many of the examples use the libc crate just for types such as `c_char` and `c_int`, which are now available through `std::os::raw`. I changed the ones that don't need to rely on libc. I'm glad to revert that part of the commit if it's unwanted churn.
We don't actually officially support this at all, and the execution engine
support in LLVM we've had to gut as it's not compiling on MinGW, so just delete
this test for now.
Previously the C type LLVMRelocMode (available as RelocMode in Rust)
was passed as is to the function.
However createTargetMachine expects a Reloc::Model, which is an enum
just one value short.
Additionally, the function was marked as requiring Reloc::Model in the
C code, but RelocMode on the Rust-side.
We now use the correct C type LLVMRelocMode and convert it to an
Optional<Reloc::Model> as expected by the createTargetMachine call the
same the original LLVMCreateTargetMachine function does.
See
c9b262bfbd/lib/Target/TargetMachineC.cpp (L104-L121)
This was found by @eddyb.
Since LLVM reversed the order of the debug info graphs, we need to have
a compile unit that exists *before* any functions (`DISubprogram`s) are
created. This allows the LLVM debug info builder to automatically link
the functions to the compile unit.
Convert built-in targets to JSON
Convert the built-in targets to JSON to ensure that the JSON parser is always fully featured. This follows on #32988 and #32847. The PR includes a number of extra commits that are just intermediate changes necessary for bisectibility and the ability to prove correctness of the change.
