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Add support for DW_FORM_data16 #797

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Merged
merged 5 commits into from
Sep 17, 2025
Merged

Add support for DW_FORM_data16 #797

merged 5 commits into from
Sep 17, 2025

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crzysdrs
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@crzysdrs crzysdrs commented Sep 11, 2025 •
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DW_FORM_data16 provided to DW_AT_upper_bound was being incorrectly being converted to an AttributeValue::Block causing the exprloc_value function to interpret it as a bunch of bytes representing an expression. This expression when parsed was an invalid set of bytes.

This can be demonstrated by running the simple_convert example over the following testcase.

Attached Example:
dw_form.tar.gz

It should be noted that the example also has line programs that are newer versions than the units they are embedded in and will fail a consistency check when writing the LineProgram. This can be ignored by commenting out the check in src/write/line.rs. See #798.

Also we are using a cherry-picked version of #787

@crzysdrs crzysdrs mentioned this pull request Sep 11, 2025
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philipc
philipc requested changes Sep 16, 2025
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Can you also add some tests for this? (They should have existed already but got missed). Two tests similar to the data8 tests should be enough (read and write).

Also note that the line program parser still reads DW_FORM_data16 as a block, but we want it to keep doing that because it's used for MD5 hashes.

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crzysdrs commented Sep 17, 2025 •
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Tests added.

It appears that the line program has its own parse_attribute function that I have not altered, so it should continue to parse data16 as Block.

There was one other concern I had around some extra logic in the parsing of data4,8 here that appears to handle some possible differences in dwarf2/3 regarding section offsets. My assumption was that this does not apply to data16 so I didn't copy this but I don't have any evidence to support that.

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philipc commented Sep 17, 2025

My assumption was that this does not apply to data16 so I didn't copy this but I don't have any evidence to support that.

Yes, not needed for data16 because there's no Format::Dwarf128.

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philipc approved these changes Sep 17, 2025
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Thanks!

@philipc philipc merged commit 5a12eb5 into gimli-rs:master Sep 17, 2025
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