43 lines
1.7 KiB
Rust
43 lines
1.7 KiB
Rust
use crate::v0;
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use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher};
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use rustc_hir::def_id::CrateNum;
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use rustc_middle::ty::{Instance, TyCtxt};
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use std::fmt::Write;
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pub(super) fn mangle<'tcx>(
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tcx: TyCtxt<'tcx>,
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instance: Instance<'tcx>,
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instantiating_crate: Option<CrateNum>,
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full_mangling_name: impl FnOnce() -> String,
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) -> String {
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// The symbol of a generic function may be scattered in multiple downstream dylibs.
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// If the symbol of a generic function still contains `crate name`, hash conflicts between the
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// generic funcion and other symbols of the same `crate` cannot be detected in time during
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// construction. This symbol conflict is left over until it occurs during run time.
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// In this case, `instantiating-crate name` is used to replace `crate name` can completely
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// eliminate the risk of the preceding potential hash conflict.
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let crate_num =
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if let Some(krate) = instantiating_crate { krate } else { instance.def_id().krate };
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let mut symbol = "_RNxC".to_string();
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v0::push_ident(tcx.crate_name(crate_num).as_str(), &mut symbol);
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let hash = tcx.with_stable_hashing_context(|mut hcx| {
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let mut hasher = StableHasher::new();
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full_mangling_name().hash_stable(&mut hcx, &mut hasher);
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hasher.finish::<Hash64>().as_u64()
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});
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push_hash64(hash, &mut symbol);
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symbol
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}
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// The hash is encoded based on `base-62` and the final terminator `_` is removed because it does
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// not help prevent hash collisions
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fn push_hash64(hash: u64, output: &mut String) {
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let hash = v0::encode_integer_62(hash);
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let hash_len = hash.len();
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let _ = write!(output, "{hash_len}H{}", &hash[..hash_len - 1]);
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}
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