Revert "Merge CrateDisambiguator into StableCrateId"

This reverts commit d0ec85d3fb6d322496cb8f4bc1c21e19f23284ad.

1 files changed, 36 insertions, 0 deletions

diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index d1d0eee365d..6485fbebd66 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -2,9 +2,11 @@ use rustc_ast::mut_visit::{visit_clobber, MutVisitor, *};
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, AttrVec, BlockCheckMode};
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 #[cfg(parallel_compiler)]
 use rustc_data_structures::jobserver;
+use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::registry::Registry;
 use rustc_metadata::dynamic_lib::DynamicLibrary;
@@ -16,6 +18,7 @@ use rustc_session::config::{self, CrateType};
 use rustc_session::config::{ErrorOutputType, Input, OutputFilenames};
 use rustc_session::lint::{self, BuiltinLintDiagnostics, LintBuffer};
 use rustc_session::parse::CrateConfig;
+use rustc_session::CrateDisambiguator;
 use rustc_session::{early_error, filesearch, output, DiagnosticOutput, Session};
 use rustc_span::edition::Edition;
 use rustc_span::lev_distance::find_best_match_for_name;
@@ -484,6 +487,39 @@ pub fn get_codegen_sysroot(
     }
 }
 
+pub(crate) fn compute_crate_disambiguator(session: &Session) -> CrateDisambiguator {
+    use std::hash::Hasher;
+
+    // The crate_disambiguator is a 128 bit hash. The disambiguator is fed
+    // into various other hashes quite a bit (symbol hashes, incr. comp. hashes,
+    // debuginfo type IDs, etc), so we don't want it to be too wide. 128 bits
+    // should still be safe enough to avoid collisions in practice.
+    let mut hasher = StableHasher::new();
+
+    let mut metadata = session.opts.cg.metadata.clone();
+    // We don't want the crate_disambiguator to dependent on the order
+    // -C metadata arguments, so sort them:
+    metadata.sort();
+    // Every distinct -C metadata value is only incorporated once:
+    metadata.dedup();
+
+    hasher.write(b"metadata");
+    for s in &metadata {
+        // Also incorporate the length of a metadata string, so that we generate
+        // different values for `-Cmetadata=ab -Cmetadata=c` and
+        // `-Cmetadata=a -Cmetadata=bc`
+        hasher.write_usize(s.len());
+        hasher.write(s.as_bytes());
+    }
+
+    // Also incorporate crate type, so that we don't get symbol conflicts when
+    // linking against a library of the same name, if this is an executable.
+    let is_exe = session.crate_types().contains(&CrateType::Executable);
+    hasher.write(if is_exe { b"exe" } else { b"lib" });
+
+    CrateDisambiguator::from(hasher.finish::<Fingerprint>())
+}
+
 pub(crate) fn check_attr_crate_type(
     sess: &Session,
     attrs: &[ast::Attribute],