Auto merge of #113695 - bjorn3:fix_rlib_cdylib_metadata_handling, r=pnkfelix,petrochenkov

Verify that all crate sources are in sync

This ensures that rustc will not attempt to link against a cdylib as if it is a rust dylib when an rlib for the same crate is available. Previously rustc didn't actually check if any further formats of a crate which has been loaded are of the same version and if they are actually valid. This caused a cdylib to be interpreted as rust dylib as soon as the corresponding rlib was loaded. As cdylibs don't export any rust symbols, linking would fail if rustc decides to link against the cdylib rather than the rlib.

Two crates depended on the previous behavior by separately compiling a test crate as both rlib and dylib. These have been changed to capture their original spirit to the best of my ability while still working when rustc verifies that all crates are in sync. It is unlikely that build systems depend on the current behavior and in any case we are taking a lot of measures to ensure that any change to either the source or the compilation options (including crate type) results in rustc rejecting it as incompatible. We merely didn't do this check here for now obsolete perf reasons.

Fixes #10786
Fixes #82151
Fixes #82972
Closes bevy-cheatbook/bevy-cheatbook#114

Author: bors

Diff for: Cargo.lock

@@ -3367,7 +3367,6 @@ dependencies = [
  "rustc_type_ir",
  "serde_json",
  "smallvec",
- "snap",
  "tempfile",
  "thorin-dwp",
  "tracing",

Diff for: compiler/rustc_codegen_ssa/Cargo.toml

@@ -17,7 +17,6 @@ tempfile = "3.2"
 thorin-dwp = "0.6"
 pathdiff = "0.2.0"
 serde_json = "1.0.59"
-snap = "1"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 regex = "1.4"
 

Diff for: compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -10,8 +10,6 @@ use object::{
     ObjectSymbol, SectionFlags, SectionKind, SymbolFlags, SymbolKind, SymbolScope,
 };
 
-use snap::write::FrameEncoder;
-
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::owned_slice::{try_slice_owned, OwnedSlice};
 use rustc_metadata::fs::METADATA_FILENAME;
@@ -481,19 +479,15 @@ pub fn create_compressed_metadata_file(
     metadata: &EncodedMetadata,
     symbol_name: &str,
 ) -> Vec<u8> {
-    let mut compressed = rustc_metadata::METADATA_HEADER.to_vec();
-    // Our length will be backfilled once we're done writing
-    compressed.write_all(&[0; 4]).unwrap();
-    FrameEncoder::new(&mut compressed).write_all(metadata.raw_data()).unwrap();
-    let meta_len = rustc_metadata::METADATA_HEADER.len();
-    let data_len = (compressed.len() - meta_len - 4) as u32;
-    compressed[meta_len..meta_len + 4].copy_from_slice(&data_len.to_be_bytes());
+    let mut packed_metadata = rustc_metadata::METADATA_HEADER.to_vec();
+    packed_metadata.write_all(&(metadata.raw_data().len() as u32).to_be_bytes()).unwrap();
+    packed_metadata.extend(metadata.raw_data());
 
     let Some(mut file) = create_object_file(sess) else {
-        return compressed.to_vec();
+        return packed_metadata.to_vec();
     };
     if file.format() == BinaryFormat::Xcoff {
-        return create_compressed_metadata_file_for_xcoff(file, &compressed, symbol_name);
+        return create_compressed_metadata_file_for_xcoff(file, &packed_metadata, symbol_name);
     }
     let section = file.add_section(
         file.segment_name(StandardSegment::Data).to_vec(),
@@ -507,14 +501,14 @@ pub fn create_compressed_metadata_file(
         }
         _ => {}
     };
-    let offset = file.append_section_data(section, &compressed, 1);
+    let offset = file.append_section_data(section, &packed_metadata, 1);
 
     // For MachO and probably PE this is necessary to prevent the linker from throwing away the
     // .rustc section. For ELF this isn't necessary, but it also doesn't harm.
     file.add_symbol(Symbol {
         name: symbol_name.as_bytes().to_vec(),
         value: offset,
-        size: compressed.len() as u64,
+        size: packed_metadata.len() as u64,
         kind: SymbolKind::Data,
         scope: SymbolScope::Dynamic,
         weak: false,

Diff for: compiler/rustc_metadata/src/locator.rs

@@ -511,7 +511,7 @@ impl<'a> CrateLocator<'a> {
             rlib: self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot)?,
             dylib: self.extract_one(dylibs, CrateFlavor::Dylib, &mut slot)?,
         };
-        Ok(slot.map(|(svh, metadata)| (svh, Library { source, metadata })))
+        Ok(slot.map(|(svh, metadata, _)| (svh, Library { source, metadata })))
     }
 
     fn needs_crate_flavor(&self, flavor: CrateFlavor) -> bool {
@@ -535,11 +535,13 @@ impl<'a> CrateLocator<'a> {
     // read the metadata from it if `*slot` is `None`. If the metadata couldn't
     // be read, it is assumed that the file isn't a valid rust library (no
     // errors are emitted).
+    //
+    // The `PathBuf` in `slot` will only be used for diagnostic purposes.
     fn extract_one(
         &mut self,
         m: FxHashMap<PathBuf, PathKind>,
         flavor: CrateFlavor,
-        slot: &mut Option<(Svh, MetadataBlob)>,
+        slot: &mut Option<(Svh, MetadataBlob, PathBuf)>,
     ) -> Result<Option<(PathBuf, PathKind)>, CrateError> {
         // If we are producing an rlib, and we've already loaded metadata, then
         // we should not attempt to discover further crate sources (unless we're
@@ -550,16 +552,9 @@ impl<'a> CrateLocator<'a> {
         //
         // See also #68149 which provides more detail on why emitting the
         // dependency on the rlib is a bad thing.
-        //
-        // We currently do not verify that these other sources are even in sync,
-        // and this is arguably a bug (see #10786), but because reading metadata
-        // is quite slow (especially from dylibs) we currently do not read it
-        // from the other crate sources.
         if slot.is_some() {
             if m.is_empty() || !self.needs_crate_flavor(flavor) {
                 return Ok(None);
-            } else if m.len() == 1 {
-                return Ok(Some(m.into_iter().next().unwrap()));
             }
         }
 
@@ -610,8 +605,7 @@ impl<'a> CrateLocator<'a> {
                         candidates,
                     ));
                 }
-                err_data = Some(vec![ret.as_ref().unwrap().0.clone()]);
-                *slot = None;
+                err_data = Some(vec![slot.take().unwrap().2]);
             }
             if let Some(candidates) = &mut err_data {
                 candidates.push(lib);
@@ -644,7 +638,7 @@ impl<'a> CrateLocator<'a> {
                     continue;
                 }
             }
-            *slot = Some((hash, metadata));
+            *slot = Some((hash, metadata, lib.clone()));
             ret = Some((lib, kind));
         }
 
@@ -814,19 +808,26 @@ fn get_metadata_section<'p>(
             let compressed_len = u32::from_be_bytes(len_bytes) as usize;
 
             // Header is okay -> inflate the actual metadata
-            let compressed_bytes = &buf[data_start..(data_start + compressed_len)];
-            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()
-                ))
-            })?;
+            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)
+                slice_owned(inflated, Deref::deref)
+            }
         }
         CrateFlavor::Rmeta => {
             // mmap the file, because only a small fraction of it is read.

Diff for: tests/run-make/extern-flag-pathless/Makefile

@@ -3,17 +3,32 @@ include ../tools.mk
 
 # Test mixing pathless --extern with paths.
 
+# Test for static linking by checking that the binary runs if the dylib
+# is removed and test for dynamic linking by checking that the binary
+# fails to run if the dylib is removed.
+
 all:
-	$(RUSTC) bar-static.rs --crate-name=bar --crate-type=rlib
-	$(RUSTC) bar-dynamic.rs --crate-name=bar --crate-type=dylib -C prefer-dynamic
+	$(RUSTC) bar.rs --crate-type=rlib --crate-type=dylib -Cprefer-dynamic
+
 	# rlib preferred over dylib
 	$(RUSTC) foo.rs --extern bar
-	$(call RUN,foo) | $(CGREP) 'static'
+	mv $(call DYLIB,bar) $(TMPDIR)/bar.tmp
+	$(call RUN,foo)
+	mv $(TMPDIR)/bar.tmp $(call DYLIB,bar)
+
 	$(RUSTC) foo.rs --extern bar=$(TMPDIR)/libbar.rlib --extern bar
-	$(call RUN,foo) | $(CGREP) 'static'
+	mv $(call DYLIB,bar) $(TMPDIR)/bar.tmp
+	$(call RUN,foo)
+	mv $(TMPDIR)/bar.tmp $(call DYLIB,bar)
+
 	# explicit --extern overrides pathless
 	$(RUSTC) foo.rs --extern bar=$(call DYLIB,bar) --extern bar
-	$(call RUN,foo) | $(CGREP) 'dynamic'
+	mv $(call DYLIB,bar) $(TMPDIR)/bar.tmp
+	$(call FAIL,foo)
+	mv $(TMPDIR)/bar.tmp $(call DYLIB,bar)
+
 	# prefer-dynamic does what it says
 	$(RUSTC) foo.rs --extern bar -C prefer-dynamic
-	$(call RUN,foo) | $(CGREP) 'dynamic'
+	mv $(call DYLIB,bar) $(TMPDIR)/bar.tmp
+	$(call FAIL,foo)
+	mv $(TMPDIR)/bar.tmp $(call DYLIB,bar)

Diff for: tests/run-make/extern-flag-pathless/bar-dynamic.rs

@@ -0,0 +1 @@
+pub fn f() {}

Diff for: tests/run-make/extern-flag-pathless/bar-static.rs

@@ -2,9 +2,7 @@
 include ../tools.mk
 
 all:
-	$(RUSTC) rlib.rs
-	$(RUSTC) dylib.rs
-	$(RUSTC) rlib.rs --crate-type=dylib
-	$(RUSTC) dylib.rs
-	$(call REMOVE_DYLIBS,rlib)
+	$(RUSTC) rlib.rs --crate-type=rlib --crate-type=dylib
+	$(RUSTC) dylib.rs # no -Cprefer-dynamic so statically linking librlib.rlib
+	$(call REMOVE_DYLIBS,rlib) # remove librlib.so to test that prog.rs doesn't get confused about the removed dylib version of librlib
 	$(RUSTC) prog.rs && exit 1 || exit 0

Diff for: tests/run-make/extern-flag-pathless/bar.rs

@@ -0,0 +1,16 @@
+# ignore-cross-compile
+include ../tools.mk
+
+# Test that rustc will not attempt to link against a cdylib as if
+# it is a rust dylib when an rlib for the same crate is available.
+# Previously rustc didn't actually check if any further formats of
+# a crate which has been loaded are of the same version and if
+# they are actually valid. This caused a cdylib to be interpreted
+# as rust dylib as soon as the corresponding rlib was loaded. As
+# cdylibs don't export any rust symbols, linking would fail if
+# rustc decides to link against the cdylib rather than the rlib.
+
+all:
+	$(RUSTC) bar.rs --crate-type=rlib --crate-type=cdylib
+	$(RUSTC) foo.rs -C prefer-dynamic
+	$(call RUN,foo)

Diff for: tests/run-make/mixing-libs/Makefile

@@ -0,0 +1 @@
+pub fn bar() {}

Diff for: tests/run-make/no-cdylib-as-rdylib/Makefile

@@ -0,0 +1,5 @@
+extern crate bar;
+
+fn main() {
+    bar::bar();
+}

Diff for: tests/run-make/no-cdylib-as-rdylib/bar.rs

@@ -0,0 +1,16 @@
+# ignore-cross-compile
+include ../tools.mk
+
+# Test that using rlibs and rmeta dep crates work together. Specifically, that
+# there can be both an rmeta and an rlib file and rustc will prefer the rmeta
+# file.
+#
+# This behavior is simply making sure this doesn't accidentally change; in this
+# case we want to make sure that the rlib isn't being used as that would cause
+# bugs in -Zbinary-dep-depinfo (see #68298).
+
+all:
+	$(RUSTC) rmeta_aux.rs --crate-type=rlib --emit link,metadata
+	$(RUSTC) lib.rs --crate-type=rlib --emit dep-info -Zbinary-dep-depinfo
+	$(CGREP) "librmeta_aux.rmeta" < $(TMPDIR)/lib.d
+	$(CGREP) -v "librmeta_aux.rlib" < $(TMPDIR)/lib.d

Diff for: tests/run-make/no-cdylib-as-rdylib/foo.rs

@@ -1,4 +1,3 @@
-// run-pass
 // Test that using rlibs and rmeta dep crates work together. Specifically, that
 // there can be both an rmeta and an rlib file and rustc will prefer the rmeta
 // file.
@@ -7,12 +6,9 @@
 // case we want to make sure that the rlib isn't being used as that would cause
 // bugs in -Zbinary-dep-depinfo (see #68298).
 
-// aux-build:rmeta-rmeta.rs
-// aux-build:rmeta-rlib-rpass.rs
-
 extern crate rmeta_aux;
 use rmeta_aux::Foo;
 
-pub fn main() {
-    let _ = Foo { field2: 42 };
+pub fn foo() {
+    let _ = Foo { field: 42 };
 }

Diff for: tests/run-make/rmeta-preferred/Makefile

@@ -0,0 +1,3 @@
+pub struct Foo {
+    pub field: i32,
+}