118 lines
4.6 KiB
Rust
118 lines
4.6 KiB
Rust
//! The compiler_builtins library is special. It can call functions in core, but it must not
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//! require linkage against a build of core. If it ever does, building the standard library *may*
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//! result in linker errors, depending on whether the linker in use applies optimizations first or
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//! resolves symbols first. So the portable and safe approach is to forbid such a linkage
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//! requirement entirely.
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//!
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//! In addition, whether compiler_builtins requires linkage against core can depend on optimization
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//! settings. Turning off optimizations and enabling debug assertions tends to produce the most
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//! dependence on core that is possible, so that is the configuration we test here.
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// wasm and nvptx targets don't produce rlib files that object can parse.
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//@ ignore-wasm
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//@ ignore-nvptx64
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#![deny(warnings)]
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use std::collections::HashSet;
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use run_make_support::object::read::Object;
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use run_make_support::object::read::archive::ArchiveFile;
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use run_make_support::object::{ObjectSection, ObjectSymbol, RelocationTarget};
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use run_make_support::rfs::{read, read_dir};
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use run_make_support::{cargo, object, path, target};
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fn main() {
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let target_dir = path("target");
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println!("Testing compiler_builtins for {}", target());
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cargo()
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.args(&[
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"build",
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"--manifest-path",
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"Cargo.toml",
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"-Zbuild-std=core",
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"--target",
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&target(),
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])
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.env("RUSTFLAGS", "-Copt-level=0 -Cdebug-assertions=yes")
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.env("CARGO_TARGET_DIR", &target_dir)
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.env("RUSTC_BOOTSTRAP", "1")
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// Visual Studio 2022 requires that the LIB env var be set so it can
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// find the Windows SDK.
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.env("LIB", std::env::var("LIB").unwrap_or_default())
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.run();
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let rlibs_path = target_dir.join(target()).join("debug").join("deps");
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let compiler_builtins_rlib = read_dir(rlibs_path)
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.find_map(|e| {
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let path = e.unwrap().path();
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let file_name = path.file_name().unwrap().to_str().unwrap();
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if file_name.starts_with("libcompiler_builtins") && file_name.ends_with(".rlib") {
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Some(path)
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} else {
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None
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}
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})
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.unwrap();
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// rlib files are archives, where the archive members each a CGU, and we also have one called
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// lib.rmeta which is the encoded metadata. Each of the CGUs is an object file.
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let data = read(compiler_builtins_rlib);
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let mut defined_symbols = HashSet::new();
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let mut undefined_relocations = HashSet::new();
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let archive = ArchiveFile::parse(&*data).unwrap();
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for member in archive.members() {
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let member = member.unwrap();
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if member.name() == b"lib.rmeta" {
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continue;
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}
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let data = member.data(&*data).unwrap();
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let object = object::File::parse(&*data).unwrap();
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// Record all defined symbols in this CGU.
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for symbol in object.symbols() {
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if !symbol.is_undefined() {
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let name = symbol.name().unwrap();
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defined_symbols.insert(name);
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}
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}
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// Find any relocations against undefined symbols. Calls within this CGU are relocations
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// against a defined symbol.
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for (_offset, relocation) in object.sections().flat_map(|section| section.relocations()) {
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let RelocationTarget::Symbol(symbol_index) = relocation.target() else {
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continue;
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};
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let symbol = object.symbol_by_index(symbol_index).unwrap();
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if symbol.is_undefined() {
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let name = symbol.name().unwrap();
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undefined_relocations.insert(name);
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}
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}
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}
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// We can have symbols in the compiler_builtins rlib that are actually from core, if they were
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// monomorphized in the compiler_builtins crate. This is totally fine, because though the call
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// is to a function in core, it's resolved internally.
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//
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// It is normal to have relocations against symbols not defined in the rlib for things like
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// unwinding, or math functions provided the target's platform libraries. Finding these is not
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// a problem, we want to specifically ban relocations against core which are not resolved
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// internally.
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undefined_relocations
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.retain(|symbol| !defined_symbols.contains(symbol) && symbol.contains("core"));
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if !undefined_relocations.is_empty() {
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panic!(
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"compiler_builtins must not link against core, but it does. \n\
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These symbols may be undefined in a debug build of compiler_builtins:\n\
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{:?}",
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undefined_relocations
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);
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}
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}
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