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Rollup merge of #137017 - bjorn3:ignore_invalid_bitcode, r=oli-obk

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Don't error when adding a staticlib with bitcode files compiled by newer LLVM

cc https://github.com/rust-lang/rust/issues/128955#issuecomment-2657811196
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许杰友 Jieyou Xu (Joe) 2025-02-28 22:29:49 +08:00 • committed by GitHub
commit 61e90040db
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3 changed files with 51 additions and 3 deletions
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25
compiler/rustc_codegen_llvm/src/back/archive.rs
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@ -132,14 +132,33 @@ fn get_llvm_object_symbols(
if err.is_null() {
return Ok(true);
} else {
return Err(unsafe { *Box::from_raw(err as *mut io::Error) });
let error = unsafe { *Box::from_raw(err as *mut io::Error) };
// These are the magic constants for LLVM bitcode files:
// https://github.com/llvm/llvm-project/blob/7eadc1960d199676f04add402bb0aa6f65b7b234/llvm/lib/BinaryFormat/Magic.cpp#L90-L97
if buf.starts_with(&[0xDE, 0xCE, 0x17, 0x0B]) || buf.starts_with(&[b'B', b'C', 0xC0, 0xDE])
{
// For LLVM bitcode, failure to read the symbols is not fatal. The bitcode may have been
// produced by a newer LLVM version that the one linked to rustc. This is fine provided
// that the linker does use said newer LLVM version. We skip writing the symbols for the
// bitcode to the symbol table of the archive. Traditional linkers don't like this, but
// newer linkers like lld, mold and wild ignore the symbol table anyway, so if they link
// against a new enough LLVM it will work out in the end.
// LLVM's archive writer also has this same behavior of only warning about invalid
// bitcode since https://github.com/llvm/llvm-project/pull/96848
// We don't have access to the DiagCtxt here to produce a nice warning in the correct format.
eprintln!("warning: Failed to read symbol table from LLVM bitcode: {}", error);
return Ok(true);
} else {
return Err(error);
}
}
unsafe extern "C" fn callback(state: *mut c_void, symbol_name: *const c_char) -> *mut c_void {
let f = unsafe { &mut *(state as *mut &mut dyn FnMut(&[u8]) -> io::Result<()>) };
match f(unsafe { CStr::from_ptr(symbol_name) }.to_bytes()) {
Ok(()) => std::ptr::null_mut(),
Err(err) => Box::into_raw(Box::new(err)) as *mut c_void,
Err(err) => Box::into_raw(Box::new(err) as Box<io::Error>) as *mut c_void,
}
}
@ -148,7 +167,7 @@ fn get_llvm_object_symbols(
Box::into_raw(Box::new(io::Error::new(
io::ErrorKind::Other,
format!("LLVM error: {}", error.to_string_lossy()),
))) as *mut c_void
)) as Box<io::Error>) as *mut c_void
}
}