[ABI] Add predicate to identify sections containing reflection data #41066
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| @@ -56,6 +65,12 @@ class SwiftObjectFileFormatMachO : public SwiftObjectFileFormat { | |||
| llvm::Optional<llvm::StringRef> getSegmentName() override { | |||
| return {"__TEXT"}; | |||
| } | |||
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| bool sectionContainsReflectionData(llvm::StringRef sectionName) override { | |||
| return sectionName.startswith("__swift5_") || | |||
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This looks sketchy: this line compares a section-name-only string and the next line a segment,section string. Does this actually work?
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i.e., why isn't this __TEXT,_swift5_?
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The caller is implemented to call first with the section name (ie __swift5_fieldmd), and then secondly call with the segment qualified name (ie __DATA,__const).
Here's that implementation: https://github.com/apple/llvm-project/pull/3848/files#diff-1c2c090c5ff772b9b304dbdd4cf45803478f4f33d11d042817fea7358e0cc96b
You'd prefer mach-o binaries call this once, and pass in a segment qualified name?
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Thanks, that makes sense! In light of the dsymutil patch that copies reflection metadata from __TEXT to __DWARF, this implementation is actually preferred.
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I added a comment to explain how the caller should call this function.
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fwiw mach-o sections have a flags field. Ideally we wouldn't check names, and instead check for a flag. But that's not something that can independently implement. |
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…ctions-containing-reflection-data [ABI] Add predicate to identify sections containing reflection data (cherry picked from commit 56a614a)
ABI/ObjectFile.habstracts reflection section names across platforms (binary file formats). However, some non-root reflection data is stored in general purpose sections, for example on Darwin type metadata can be placed in__DATA_CONST,__const, such as data that has loader fixups (bindings or relocations).This change introduces a new predicate function to check if a section name could contain reflection data. These are the swift specific reflections sections, as well as general purpose sections that vary by platform. This initial change adds
__DATA_CONST,__constfor Mach-O files.This will be used by overrides of
MemoryReader::resolvePointer, to know whether an address is from a reflection section or not. If the section doesn't contain reflection data, thenresolvePointershould not return a symbol.