Make the metadata lock more robust #34539
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The refactorings here all look good to me, but I thought we already had a system like this for breaking changes to metadata? This constant is in theory updated for all major version changes to metadata, although it was last updated 2015-03-02 so it's not exactly updated that often... It seems to me that even with a json header we'd still have to actively go and bump the version number, so we'd largely be in the same situation we're in today? I'm curious, though, is there a particular reason you'd want to switch to a json header rather than just a version number stored at the front? |
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The loader needs to load a few fields before it can figure out whether it should load a crate or not. I prefer keeping these fields separate from the rest, to prevent us from changing them and causing a recurrence of this issue. |
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Yeah the loader will definitely always have to load something at least, I think I'm just not connecting the dots as to why today's implementation (just a version number in the first N bytes) is either better or worse than encoding information as JSON. We can perhaps provide a better diagnostic in the case where JSON is used because we can be sure that some fields are always there, but I'm not sure it's worth the implementation overhead because this in theory should basically never happen. In other words, I don't think this is technically buying us anything because if we bumped the metadata version then all historical compilers would automatically be unable to read future compilers' metadata. |
arielb1
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updated to use a simpler approach. |
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Apparently the error message for corrupt metadata is broken: Wait. We don't have metadata encoding version on rlibs. at all. @bors r- for now. Will re-r= after I fix that. |
…sion check the metadata lock when loading rather than afterwards Fixes rust-lang#33733 Fixes rust-lang#33015
previously, only .so files included a metadata encoding version, *outside* of the zlib compressed area. This adds an encoding version inside the metadata itself, in both .so and .rlib files. Fixes rust-lang#33778.
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@bors r=alexcrichton |
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📌 Commit 42b7c32 has been approved by |
Make the metadata lock more robust Fixes #33778 and friends. I also needed to add a metadata encoding version to rlibs, as they did not have it before. To keep it backwards-compatible, I added 4 zeroes to the start of the metadata, which are treated as an empty length field by older rustcs. r? @alexcrichton
Fixes #33778 and friends.
I also needed to add a metadata encoding version to rlibs, as they did not have it before. To keep it backwards-compatible, I added 4 zeroes to the start of the metadata, which are treated as an empty length field by older rustcs.
r? @alexcrichton