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Auto merge of #118344 - saethlin:rmeta-header-pos, r=WaffleLapkin
Use a u64 for the rmeta root position
Waffle noticed this in https://github.com/rust-lang/rust/pull/117301#discussion_r1405410174
We've upgraded the other file offsets to u64, and this one only costs 4 bytes per file. Also the way the truncation was being done before was extremely easy to miss, I sure missed it! It's not clear to me if not having this change effectively made the other upgrades from u32 to u64 ineffective, but we can have it now.
r? `@WaffleLapkin`
| -rw-r--r-- | crates/proc-macro-api/src/version.rs | 31 |
1 files changed, 18 insertions, 13 deletions
diff --git a/crates/proc-macro-api/src/version.rs b/crates/proc-macro-api/src/version.rs index 48efbf589c..87118a6265 100644 --- a/crates/proc-macro-api/src/version.rs +++ b/crates/proc-macro-api/src/version.rs @@ -85,8 +85,8 @@ fn read_section<'a>(dylib_binary: &'a [u8], section_name: &str) -> io::Result<&' } /// Check the version of rustc that was used to compile a proc macro crate's -/// /// binary file. +/// /// A proc macro crate binary's ".rustc" section has following byte layout: /// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes /// * ff060000 734e6150 is followed, it's the snappy format magic bytes, @@ -96,8 +96,8 @@ fn read_section<'a>(dylib_binary: &'a [u8], section_name: &str) -> io::Result<&' /// The bytes you get after decompressing the snappy format portion has /// following layout: /// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes(again) -/// * [crate root bytes] next 4 bytes is to store crate root position, -/// according to rustc's source code comment +/// * [crate root bytes] next 8 bytes (4 in old versions) is to store +/// crate root position, according to rustc's source code comment /// * [length byte] next 1 byte tells us how many bytes we should read next /// for the version string's utf8 bytes /// * [version string bytes encoded in utf8] <- GET THIS BOI @@ -119,14 +119,19 @@ 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/0696e79f2740ad89309269b460579e548a5cd632 - let snappy_portion = match version { - 5 | 6 => &dot_rustc[8..], + // 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 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] + (&dot_rustc[12..data_len + 12], 13) } + 9 => { + let len_bytes = &dot_rustc[8..16]; + let data_len = u64::from_le_bytes(len_bytes.try_into().unwrap()) as usize; + (&dot_rustc[16..data_len + 12], 17) + } _ => { return Err(io::Error::new( io::ErrorKind::InvalidData, @@ -142,15 +147,15 @@ pub fn read_version(dylib_path: &AbsPath) -> io::Result<String> { Box::new(SnapDecoder::new(snappy_portion)) }; - // the bytes before version string bytes, so this basically is: + // 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 bytes for [crate root bytes] + // 4 or 8 bytes for [crate root bytes] // 1 byte for length of version string - // so 13 bytes in total, and we should check the 13th byte + // so 13 or 17 bytes in total, and we should check the last of those bytes // to know the length - let mut bytes_before_version = [0u8; 13]; - uncompressed.read_exact(&mut bytes_before_version)?; - let length = bytes_before_version[12]; + let mut bytes = [0u8; 17]; + uncompressed.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)?; |