Auto merge of rust-lang#132402 - bjorn3:remove_snap_decompression, r=jieyouxu,Veykril

Remove support for decompressing dylib metadata

We haven't been compressing dylib metadata for a while now. Removing decompression support will regress error messages about an incompatible rustc version being used, but dylibs are pretty rare anyway.

Fixes rust-lang/rust-analyzer#18451

Author: bors

Cargo.lock

@@ -4006,7 +4006,6 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_type_ir",
- "snap",
  "tempfile",
  "tracing",
 ]
@@ -4891,12 +4890,6 @@ version = "1.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c5e1a9a646d36c3599cd173a41282daf47c44583ad367b8e6837255952e5c67"
 
-[[package]]
-name = "snap"
-version = "1.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b6b67fb9a61334225b5b790716f609cd58395f895b3fe8b328786812a40bc3b"
-
 [[package]]
 name = "socket2"
 version = "0.5.7"

compiler/rustc_metadata/Cargo.toml

@@ -27,7 +27,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_type_ir = { path = "../rustc_type_ir" }
-snap = "1"
 tempfile = "3.2"
 tracing = "0.1"
 # tidy-alphabetical-end

compiler/rustc_metadata/src/locator.rs

@@ -213,7 +213,7 @@
 //! metadata::locator or metadata::creader for all the juicy details!
 
 use std::borrow::Cow;
-use std::io::{Read, Result as IoResult, Write};
+use std::io::{Result as IoResult, Write};
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::{cmp, fmt};
@@ -232,7 +232,6 @@ use rustc_session::utils::CanonicalizedPath;
 use rustc_span::Span;
 use rustc_span::symbol::Symbol;
 use rustc_target::spec::{Target, TargetTriple};
-use snap::read::FrameDecoder;
 use tracing::{debug, info};
 
 use crate::creader::{Library, MetadataLoader};
@@ -792,7 +791,6 @@ fn get_metadata_section<'p>(
         CrateFlavor::Dylib => {
             let buf =
                 loader.get_dylib_metadata(target, filename).map_err(MetadataError::LoadFailure)?;
-            // The header is uncompressed
             let header_len = METADATA_HEADER.len();
             // header + u64 length of data
             let data_start = header_len + 8;
@@ -806,37 +804,18 @@ fn get_metadata_section<'p>(
                 )));
             }
 
-            // Length of the compressed stream - this allows linkers to pad the section if they want
+            // Length of the metadata - this allows linkers to pad the section if they want
             let Ok(len_bytes) =
                 <[u8; 8]>::try_from(&buf[header_len..cmp::min(data_start, buf.len())])
             else {
                 return Err(MetadataError::LoadFailure(
                     "invalid metadata length found".to_string(),
                 ));
             };
-            let compressed_len = u64::from_le_bytes(len_bytes) as usize;
+            let metadata_len = u64::from_le_bytes(len_bytes) as usize;
 
             // Header is okay -> inflate the actual metadata
-            let compressed_bytes = buf.slice(|buf| &buf[data_start..(data_start + compressed_len)]);
-            if &compressed_bytes[..cmp::min(METADATA_HEADER.len(), compressed_bytes.len())]
-                == METADATA_HEADER
-            {
-                // The metadata was not actually compressed.
-                compressed_bytes
-            } else {
-                debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
-                // Assume the decompressed data will be at least the size of the compressed data, so we
-                // don't have to grow the buffer as much.
-                let mut inflated = Vec::with_capacity(compressed_bytes.len());
-                FrameDecoder::new(&*compressed_bytes).read_to_end(&mut inflated).map_err(|_| {
-                    MetadataError::LoadFailure(format!(
-                        "failed to decompress metadata: {}",
-                        filename.display()
-                    ))
-                })?;
-
-                slice_owned(inflated, Deref::deref)
-            }
+            buf.slice(|buf| &buf[data_start..(data_start + metadata_len)])
         }
         CrateFlavor::Rmeta => {
             // mmap the file, because only a small fraction of it is read.

src/tools/rust-analyzer/Cargo.lock

@@ -1364,7 +1364,6 @@ dependencies = [
  "proc-macro-api",
  "proc-macro-test",
  "ra-ap-rustc_lexer",
- "snap",
  "span",
  "stdx",
  "syntax-bridge",
@@ -1888,12 +1887,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "snap"
-version = "1.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b6b67fb9a61334225b5b790716f609cd58395f895b3fe8b328786812a40bc3b"
-
 [[package]]
 name = "span"
 version = "0.0.0"

src/tools/rust-analyzer/Cargo.toml

@@ -145,7 +145,6 @@ smallvec = { version = "1.10.0", features = [
   "const_generics",
 ] }
 smol_str = "0.3.2"
-snap = "1.1.0"
 text-size = "1.1.1"
 tracing = "0.1.40"
 tracing-tree = "0.3.0"

src/tools/rust-analyzer/crates/proc-macro-srv/Cargo.toml

@@ -16,7 +16,6 @@ doctest = false
 object.workspace = true
 libloading.workspace = true
 memmap2.workspace = true
-snap.workspace = true
 
 stdx.workspace = true
 tt.workspace = true

src/tools/rust-analyzer/crates/proc-macro-srv/src/dylib/version.rs

@@ -8,7 +8,6 @@ use std::{
 use memmap2::Mmap;
 use object::read::{File as BinaryFile, Object, ObjectSection};
 use paths::AbsPath;
-use snap::read::FrameDecoder as SnapDecoder;
 
 #[derive(Debug)]
 #[allow(dead_code)]
@@ -123,9 +122,8 @@ pub fn read_version(dylib_path: &AbsPath) -> io::Result<String> {
     let version = u32::from_be_bytes([dot_rustc[4], dot_rustc[5], dot_rustc[6], dot_rustc[7]]);
     // Last supported version is:
     // https://github.com/rust-lang/rust/commit/b94cfefc860715fb2adf72a6955423d384c69318
-    let (snappy_portion, bytes_before_version) = match version {
-        5 | 6 => (&dot_rustc[8..], 13),
-        7 | 8 => {
+    let (mut metadata_portion, bytes_before_version) = match version {
+        8 => {
             let len_bytes = &dot_rustc[8..12];
             let data_len = u32::from_be_bytes(len_bytes.try_into().unwrap()) as usize;
             (&dot_rustc[12..data_len + 12], 13)
@@ -143,25 +141,18 @@ pub fn read_version(dylib_path: &AbsPath) -> io::Result<String> {
         }
     };
 
-    let mut uncompressed: Box<dyn Read> = if &snappy_portion[0..4] == b"rust" {
-        // Not compressed.
-        Box::new(snappy_portion)
-    } else {
-        Box::new(SnapDecoder::new(snappy_portion))
-    };
-
     // We're going to skip over the bytes before the version string, so basically:
     // 8 bytes for [b'r',b'u',b's',b't',0,0,0,5]
     // 4 or 8 bytes for [crate root bytes]
     // 1 byte for length of version string
     // so 13 or 17 bytes in total, and we should check the last of those bytes
     // to know the length
     let mut bytes = [0u8; 17];
-    uncompressed.read_exact(&mut bytes[..bytes_before_version])?;
+    metadata_portion.read_exact(&mut bytes[..bytes_before_version])?;
     let length = bytes[bytes_before_version - 1];
 
     let mut version_string_utf8 = vec![0u8; length as usize];
-    uncompressed.read_exact(&mut version_string_utf8)?;
+    metadata_portion.read_exact(&mut version_string_utf8)?;
     let version_string = String::from_utf8(version_string_utf8);
     version_string.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
 }

src/tools/tidy/src/deps.rs

@@ -101,7 +101,6 @@ const EXCEPTIONS: ExceptionList = &[
     ("rustc_apfloat", "Apache-2.0 WITH LLVM-exception"),     // rustc (license is the same as LLVM uses)
     ("ryu", "Apache-2.0 OR BSL-1.0"), // BSL is not acceptble, but we use it under Apache-2.0                       // cargo/... (because of serde)
     ("self_cell", "Apache-2.0"),                             // rustc (fluent translations)
-    ("snap", "BSD-3-Clause"),                                // rustc
     ("wasi-preview1-component-adapter-provider", "Apache-2.0 WITH LLVM-exception"), // rustc
     // tidy-alphabetical-end
 ];
@@ -163,7 +162,6 @@ const EXCEPTIONS_RUST_ANALYZER: ExceptionList = &[
     ("rustc_apfloat", "Apache-2.0 WITH LLVM-exception"),
     ("ryu", "Apache-2.0 OR BSL-1.0"), // BSL is not acceptble, but we use it under Apache-2.0
     ("scip", "Apache-2.0"),
-    ("snap", "BSD-3-Clause"),
     // tidy-alphabetical-end
 ];
 
@@ -391,7 +389,6 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "sharded-slab",
     "shlex",
     "smallvec",
-    "snap",
     "stable_deref_trait",
     "stacker",
     "static_assertions",