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Rollup merge of #121392 - bjorn3:unify_dylib_loading, r=petrochenkov
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Unify dylib loading between proc macros and codegen backends

As bonus this makes the errors when failing to load a proc macro more informative to match the backend loading errors. In addition it makes it slightly easier to patch rustc to work on platforms that don't support dynamic linking like wasm.
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matthiaskrgr authored Feb 21, 2024
2 parents 60cb794 + f25c90a commit 64dbc3f
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Showing 9 changed files with 60 additions and 45 deletions.
1 change: 0 additions & 1 deletion Cargo.lock
Original file line number Diff line number Diff line change
Expand Up @@ -4048,7 +4048,6 @@ dependencies = [
name = "rustc_interface"
version = "0.0.0"
dependencies = [
"libloading",
"rustc-rayon",
"rustc-rayon-core",
"rustc_ast",
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1 change: 0 additions & 1 deletion compiler/rustc_interface/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ edition = "2021"

[dependencies]
# tidy-alphabetical-start
libloading = "0.8.0"
rustc-rayon = { version = "0.5.0", optional = true }
rustc-rayon-core = { version = "0.5.0", optional = true }
rustc_ast = { path = "../rustc_ast" }
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1 change: 0 additions & 1 deletion compiler/rustc_interface/src/lib.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
#![feature(decl_macro)]
#![feature(error_iter)]
#![feature(generic_nonzero)]
#![feature(lazy_cell)]
#![feature(let_chains)]
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33 changes: 11 additions & 22 deletions compiler/rustc_interface/src/util.rs
Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
use crate::errors;
use info;
use libloading::Library;
use rustc_ast as ast;
use rustc_codegen_ssa::traits::CodegenBackend;
#[cfg(parallel_compiler)]
use rustc_data_structures::sync;
use rustc_metadata::{load_symbol_from_dylib, DylibError};
use rustc_parse::validate_attr;
use rustc_session as session;
use rustc_session::config::{self, Cfg, CrateType, OutFileName, OutputFilenames, OutputTypes};
Expand All @@ -17,7 +17,6 @@ use rustc_span::symbol::{sym, Symbol};
use session::EarlyDiagCtxt;
use std::env;
use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
use std::mem;
use std::path::{Path, PathBuf};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::OnceLock;
Expand Down Expand Up @@ -162,29 +161,19 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
}

fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBackendFn {
fn format_err(e: &(dyn std::error::Error + 'static)) -> String {
e.sources().map(|e| format!(": {e}")).collect()
}
let lib = unsafe { Library::new(path) }.unwrap_or_else(|err| {
let err = format!("couldn't load codegen backend {path:?}{}", format_err(&err));
early_dcx.early_fatal(err);
});

let backend_sym = unsafe { lib.get::<MakeBackendFn>(b"__rustc_codegen_backend") }
.unwrap_or_else(|e| {
match unsafe { load_symbol_from_dylib::<MakeBackendFn>(path, "__rustc_codegen_backend") } {
Ok(backend_sym) => backend_sym,
Err(DylibError::DlOpen(path, err)) => {
let err = format!("couldn't load codegen backend {path}{err}");
early_dcx.early_fatal(err);
}
Err(DylibError::DlSym(_path, err)) => {
let e = format!(
"`__rustc_codegen_backend` symbol lookup in the codegen backend failed{}",
format_err(&e)
"`__rustc_codegen_backend` symbol lookup in the codegen backend failed{err}",
);
early_dcx.early_fatal(e);
});

// Intentionally leak the dynamic library. We can't ever unload it
// since the library can make things that will live arbitrarily long.
let backend_sym = unsafe { backend_sym.into_raw() };
mem::forget(lib);

*backend_sym
}
}
}

/// Get the codegen backend based on the name and specified sysroot.
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2 changes: 1 addition & 1 deletion compiler/rustc_metadata/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ metadata_crate_not_panic_runtime =
the crate `{$crate_name}` is not a panic runtime
metadata_dl_error =
{$err}
{$path}{$err}
metadata_empty_link_name =
link name must not be empty
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56 changes: 41 additions & 15 deletions compiler/rustc_metadata/src/creader.rs
Original file line number Diff line number Diff line change
Expand Up @@ -692,20 +692,8 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
path: &Path,
stable_crate_id: StableCrateId,
) -> Result<&'static [ProcMacro], CrateError> {
// Make sure the path contains a / or the linker will search for it.
let path = try_canonicalize(path).unwrap();
let lib = load_dylib(&path, 5).map_err(|err| CrateError::DlOpen(err))?;

let sym_name = self.sess.generate_proc_macro_decls_symbol(stable_crate_id);
let sym = unsafe { lib.get::<*const &[ProcMacro]>(sym_name.as_bytes()) }
.map_err(|err| CrateError::DlSym(err.to_string()))?;

// Intentionally leak the dynamic library. We can't ever unload it
// since the library can make things that will live arbitrarily long.
let sym = unsafe { sym.into_raw() };
std::mem::forget(lib);

Ok(unsafe { **sym })
Ok(unsafe { *load_symbol_from_dylib::<*const &[ProcMacro]>(path, &sym_name)? })
}

fn inject_panic_runtime(&mut self, krate: &ast::Crate) {
Expand Down Expand Up @@ -1116,6 +1104,10 @@ fn alloc_error_handler_spans(krate: &ast::Crate) -> Vec<Span> {
f.spans
}

fn format_dlopen_err(e: &(dyn std::error::Error + 'static)) -> String {
e.sources().map(|e| format!(": {e}")).collect()
}

// On Windows the compiler would sometimes intermittently fail to open the
// proc-macro DLL with `Error::LoadLibraryExW`. It is suspected that something in the
// system still holds a lock on the file, so we retry a few times before calling it
Expand Down Expand Up @@ -1154,9 +1146,43 @@ fn load_dylib(path: &Path, max_attempts: usize) -> Result<libloading::Library, S

let last_error = last_error.unwrap();
let message = if let Some(src) = last_error.source() {
format!("{last_error} ({src}) (retried {max_attempts} times)")
format!("{} ({src}) (retried {max_attempts} times)", format_dlopen_err(&last_error))
} else {
format!("{last_error} (retried {max_attempts} times)")
format!("{} (retried {max_attempts} times)", format_dlopen_err(&last_error))
};
Err(message)
}

pub enum DylibError {
DlOpen(String, String),
DlSym(String, String),
}

impl From<DylibError> for CrateError {
fn from(err: DylibError) -> CrateError {
match err {
DylibError::DlOpen(path, err) => CrateError::DlOpen(path, err),
DylibError::DlSym(path, err) => CrateError::DlSym(path, err),
}
}
}

pub unsafe fn load_symbol_from_dylib<T: Copy>(
path: &Path,
sym_name: &str,
) -> Result<T, DylibError> {
// Make sure the path contains a / or the linker will search for it.
let path = try_canonicalize(path).unwrap();
let lib =
load_dylib(&path, 5).map_err(|err| DylibError::DlOpen(path.display().to_string(), err))?;

let sym = unsafe { lib.get::<T>(sym_name.as_bytes()) }
.map_err(|err| DylibError::DlSym(path.display().to_string(), format_dlopen_err(&err)))?;

// Intentionally leak the dynamic library. We can't ever unload it
// since the library can make things that will live arbitrarily long.
let sym = unsafe { sym.into_raw() };
std::mem::forget(lib);

Ok(*sym)
}
1 change: 1 addition & 0 deletions compiler/rustc_metadata/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -535,6 +535,7 @@ pub struct StableCrateIdCollision {
pub struct DlError {
#[primary_span]
pub span: Span,
pub path: String,
pub err: String,
}

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2 changes: 2 additions & 0 deletions compiler/rustc_metadata/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#![feature(rustdoc_internals)]
#![allow(internal_features)]
#![feature(decl_macro)]
#![feature(error_iter)]
#![feature(extract_if)]
#![feature(coroutines)]
#![feature(generic_nonzero)]
Expand Down Expand Up @@ -39,6 +40,7 @@ pub mod errors;
pub mod fs;
pub mod locator;

pub use creader::{load_symbol_from_dylib, DylibError};
pub use fs::{emit_wrapper_file, METADATA_FILENAME};
pub use native_libs::find_native_static_library;
pub use rmeta::{encode_metadata, rendered_const, EncodedMetadata, METADATA_HEADER};
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8 changes: 4 additions & 4 deletions compiler/rustc_metadata/src/locator.rs
Original file line number Diff line number Diff line change
Expand Up @@ -921,8 +921,8 @@ pub(crate) enum CrateError {
MultipleCandidates(Symbol, CrateFlavor, Vec<PathBuf>),
SymbolConflictsCurrent(Symbol),
StableCrateIdCollision(Symbol, Symbol),
DlOpen(String),
DlSym(String),
DlOpen(String, String),
DlSym(String, String),
LocatorCombined(Box<CombinedLocatorError>),
NotFound(Symbol),
}
Expand Down Expand Up @@ -967,8 +967,8 @@ impl CrateError {
CrateError::StableCrateIdCollision(crate_name0, crate_name1) => {
dcx.emit_err(errors::StableCrateIdCollision { span, crate_name0, crate_name1 });
}
CrateError::DlOpen(s) | CrateError::DlSym(s) => {
dcx.emit_err(errors::DlError { span, err: s });
CrateError::DlOpen(path, err) | CrateError::DlSym(path, err) => {
dcx.emit_err(errors::DlError { span, path, err });
}
CrateError::LocatorCombined(locator) => {
let crate_name = locator.crate_name;
Expand Down

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