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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -4,4 +4,5 @@ version = "0.0.0" | |
| edition = "2021" | ||
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| [dependencies] | ||
| object = "0.34.0" | ||
| wasmparser = "0.118.2" | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,142 @@ | ||
| //! The compiler_builtins library is special. It can call functions in core, but it must not | ||
| //! require linkage against a build of core. If it ever does, building the standard library *may* | ||
| //! result in linker errors, depending on whether the linker in use applies optimizations first or | ||
| //! resolves symbols first. So the portable and safe approach is to forbid such a linkage | ||
| //! requirement entirely. | ||
| //! | ||
| //! In addition, whether compiler_builtins requires linkage against core can depend on optimization | ||
| //! settings. Turning off optimizations and enabling debug assertions tends to produce the most | ||
| //! dependence on core that is possible, so that is the configuration we test here. | ||
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| #![deny(warnings)] | ||
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| extern crate run_make_support; | ||
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| use run_make_support::object; | ||
| use run_make_support::object::read::archive::ArchiveFile; | ||
| use run_make_support::object::read::Object; | ||
| use run_make_support::object::ObjectSection; | ||
| use run_make_support::object::ObjectSymbol; | ||
| use run_make_support::object::RelocationTarget; | ||
| use run_make_support::out_dir; | ||
| use std::collections::HashSet; | ||
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| const MANIFEST: &str = r#" | ||
| [package] | ||
| name = "scratch" | ||
| version = "0.1.0" | ||
| edition = "2021" | ||
| [lib] | ||
| path = "lib.rs""#; | ||
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| fn main() { | ||
| let target_dir = out_dir().join("target"); | ||
| let target = std::env::var("TARGET").unwrap(); | ||
| if target.starts_with("wasm") || target.starts_with("nvptx") { | ||
| // wasm and nvptx targets don't produce rlib files that object can parse. | ||
| return; | ||
| } | ||
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| println!("Testing compiler_builtins for {}", target); | ||
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| // Set up the tiniest Cargo project: An empty no_std library. Just enough to run -Zbuild-std. | ||
| let manifest_path = out_dir().join("Cargo.toml"); | ||
| std::fs::write(&manifest_path, MANIFEST.as_bytes()).unwrap(); | ||
| std::fs::write(out_dir().join("lib.rs"), b"#![no_std]").unwrap(); | ||
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| let path = std::env::var("PATH").unwrap(); | ||
| let rustc = std::env::var("RUSTC").unwrap(); | ||
| let bootstrap_cargo = std::env::var("BOOTSTRAP_CARGO").unwrap(); | ||
| let status = std::process::Command::new(bootstrap_cargo) | ||
| .args([ | ||
| "build", | ||
| "--manifest-path", | ||
| manifest_path.to_str().unwrap(), | ||
| "-Zbuild-std=core", | ||
| "--target", | ||
| &target, | ||
| ]) | ||
| .env_clear() | ||
| .env("PATH", path) | ||
| .env("RUSTC", rustc) | ||
| .env("RUSTFLAGS", "-Copt-level=0 -Cdebug-assertions=yes") | ||
| .env("CARGO_TARGET_DIR", &target_dir) | ||
| .env("RUSTC_BOOTSTRAP", "1") | ||
| .status() | ||
| .unwrap(); | ||
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| assert!(status.success()); | ||
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| let rlibs_path = target_dir.join(target).join("debug").join("deps"); | ||
| let compiler_builtins_rlib = std::fs::read_dir(rlibs_path) | ||
| .unwrap() | ||
| .find_map(|e| { | ||
| let path = e.unwrap().path(); | ||
| let file_name = path.file_name().unwrap().to_str().unwrap(); | ||
| if file_name.starts_with("libcompiler_builtins") && file_name.ends_with(".rlib") { | ||
| Some(path) | ||
| } else { | ||
| None | ||
| } | ||
| }) | ||
| .unwrap(); | ||
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| // rlib files are archives, where the archive members each a CGU, and we also have one called | ||
| // lib.rmeta which is the encoded metadata. Each of the CGUs is an object file. | ||
| let data = std::fs::read(compiler_builtins_rlib).unwrap(); | ||
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| let mut defined_symbols = HashSet::new(); | ||
| let mut undefined_relocations = HashSet::new(); | ||
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| let archive = ArchiveFile::parse(&*data).unwrap(); | ||
| for member in archive.members() { | ||
| let member = member.unwrap(); | ||
| if member.name() == b"lib.rmeta" { | ||
| continue; | ||
| } | ||
| let data = member.data(&*data).unwrap(); | ||
| let object = object::File::parse(&*data).unwrap(); | ||
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| // Record all defined symbols in this CGU. | ||
| for symbol in object.symbols() { | ||
| if !symbol.is_undefined() { | ||
| let name = symbol.name().unwrap(); | ||
| defined_symbols.insert(name); | ||
| } | ||
| } | ||
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| // Find any relocations against undefined symbols. Calls within this CGU are relocations | ||
| // against a defined symbol. | ||
| for (_offset, relocation) in object.sections().flat_map(|section| section.relocations()) { | ||
| let RelocationTarget::Symbol(symbol_index) = relocation.target() else { | ||
| continue; | ||
| }; | ||
| let symbol = object.symbol_by_index(symbol_index).unwrap(); | ||
| if symbol.is_undefined() { | ||
| let name = symbol.name().unwrap(); | ||
| undefined_relocations.insert(name); | ||
| } | ||
| } | ||
| } | ||
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| // We can have symbols in the compiler_builtins rlib that are actually from core, if they were | ||
| // monomorphized in the compiler_builtins crate. This is totally fine, because though the call | ||
| // is to a function in core, it's resolved internally. | ||
| // | ||
| // It is normal to have relocations against symbols not defined in the rlib for things like | ||
| // unwinding, or math functions provided the target's platform libraries. Finding these is not | ||
| // a problem, we want to specifically ban relocations against core which are not resolved | ||
| // internally. | ||
| undefined_relocations | ||
| .retain(|symbol| !defined_symbols.contains(symbol) && symbol.contains("core")); | ||
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| if !undefined_relocations.is_empty() { | ||
| panic!( | ||
| "compiler_builtins must not link against core, but it does. \n\ | ||
| These symbols may be undefined in a debug build of compiler_builtins:\n\ | ||
| {:?}", | ||
| undefined_relocations | ||
| ); | ||
| } | ||
| } |