Ignore missing CUs in DWARF rewriting #3700
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
aardappel
approved these changes
Mar 18, 2021
| @@ -151,6 +151,7 @@ struct LineTableOpcode { | |||
| }; | |||
|
|
|||
| struct LineTable { | |||
| uint64_t Position; // XXX BINARYEN: the binary location in .debug_line | |||
There was a problem hiding this comment.
This is set but not used anywhere in this PR?
There was a problem hiding this comment.
It's used here: https://github.com/WebAssembly/binaryen/pull/3700/files#diff-62256ba16b71cbddf493d990a92cc71e51a3f2ae0a57289ae85ae5d794db3d31R765
We set this during load. During rewrite, we read these values so we know the old position. (We also update it there, although we do not currently read at any later time - I added that to avoid future confusion, seems best to the keep the IR consistent.)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
A recent change in LLVM causes it to sometimes end up with a thing
with no parent. That is, a debug_line or a debug_loc that has no CU that
refers to it. This is perhaps LLVM DCEing CUs, or something else that
changed - not sure. But it seems like valid DWARF we should handle.
This PR handles that in our code. Two things broke here. First, locs must
be simply ignored when there is no CU. Second, lines are trickier as we
used to compute their position by scanning them, and that list contained
only ones with a CU. So we missed some and ended up with wrong offsets.
To make things simpler and more robust, just track the position of each
line table on itself.
Fixes #3697