Parse and set Mach-O section type and attributes#1648
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madsmtm
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Apr 19, 2026
| // We support the same custom section type / attrs naming as LLVM: | ||
| // <https://github.com/llvm/llvm-project/blob/llvmorg-22.1.3/llvm/lib/MC/MCSectionMachO.cpp#L23-L91> | ||
| // <https://github.com/llvm/llvm-project/blob/llvmorg-22.1.3/llvm/include/llvm/BinaryFormat/MachO.h#L120-L223> | ||
| const MACHO_SECTION_TYPES: &[(&str, u32)] = &[ |
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I did this as a table originally because I kinda wanted to print the available options / have suggestions for mistyped section types, but I ended up not implementing that, because I didn't really know if there were a good way to do so with rustc's diagnostic APIs?
I can do a match instead if you prefer?
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Using tables here is fine by me.
This was referenced Apr 19, 2026
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…trs, r=bjorn3 Add a test for Mach-O `#[link_section]` API inherited from LLVM The format of the `#[link_section]` attribute is under-documented, but on Mach-O, I think it's roughly the following BNF: ``` LinkSection -> Segment `,` Section (`,` (SectionType (`,` (SectionAttributes)?)?)?)? Segment -> <0 to 16 bytes> Section -> <0 to 16 bytes> SectionType -> `regular` | `zerofill` | `cstring_literals` | `4byte_literals` | `8byte_literals` | `literal_pointers` | `non_lazy_symbol_pointers` | `lazy_symbol_pointers` | `symbol_stubs` | `mod_init_funcs` | `mod_term_funcs` | `coalesced` | `interposing` | `16byte_literals` | `thread_local_regular` | `thread_local_zerofill` | `thread_local_variables` | `thread_local_variable_pointers` | `thread_local_init_function_pointers` SectionAttributes -> SectionAttribute (`+` SectionAttribute)* SectionAttribute -> `pure_instructions` | `no_toc` | `strip_static_syms` | `no_dead_strip` | `live_support`, `self_modifying_code` | `debug` ``` This PR adds a small test for a little part of this. Once rust-lang#154429 is resolved, this should make it possible to test rust-lang/rustc_codegen_cranelift#1648 end-to-end. r? bjorn3
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Rollup merge of #155517 - madsmtm:test-macho-link-section-attrs, r=bjorn3 Add a test for Mach-O `#[link_section]` API inherited from LLVM The format of the `#[link_section]` attribute is under-documented, but on Mach-O, I think it's roughly the following BNF: ``` LinkSection -> Segment `,` Section (`,` (SectionType (`,` (SectionAttributes)?)?)?)? Segment -> <0 to 16 bytes> Section -> <0 to 16 bytes> SectionType -> `regular` | `zerofill` | `cstring_literals` | `4byte_literals` | `8byte_literals` | `literal_pointers` | `non_lazy_symbol_pointers` | `lazy_symbol_pointers` | `symbol_stubs` | `mod_init_funcs` | `mod_term_funcs` | `coalesced` | `interposing` | `16byte_literals` | `thread_local_regular` | `thread_local_zerofill` | `thread_local_variables` | `thread_local_variable_pointers` | `thread_local_init_function_pointers` SectionAttributes -> SectionAttribute (`+` SectionAttribute)* SectionAttribute -> `pure_instructions` | `no_toc` | `strip_static_syms` | `no_dead_strip` | `live_support`, `self_modifying_code` | `debug` ``` This PR adds a small test for a little part of this. Once #154429 is resolved, this should make it possible to test rust-lang/rustc_codegen_cranelift#1648 end-to-end. r? bjorn3
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…orn3 Add a test for Mach-O `#[link_section]` API inherited from LLVM The format of the `#[link_section]` attribute is under-documented, but on Mach-O, I think it's roughly the following BNF: ``` LinkSection -> Segment `,` Section (`,` (SectionType (`,` (SectionAttributes)?)?)?)? Segment -> <0 to 16 bytes> Section -> <0 to 16 bytes> SectionType -> `regular` | `zerofill` | `cstring_literals` | `4byte_literals` | `8byte_literals` | `literal_pointers` | `non_lazy_symbol_pointers` | `lazy_symbol_pointers` | `symbol_stubs` | `mod_init_funcs` | `mod_term_funcs` | `coalesced` | `interposing` | `16byte_literals` | `thread_local_regular` | `thread_local_zerofill` | `thread_local_variables` | `thread_local_variable_pointers` | `thread_local_init_function_pointers` SectionAttributes -> SectionAttribute (`+` SectionAttribute)* SectionAttribute -> `pure_instructions` | `no_toc` | `strip_static_syms` | `no_dead_strip` | `live_support`, `self_modifying_code` | `debug` ``` This PR adds a small test for a little part of this. Once rust-lang/rust#154429 is resolved, this should make it possible to test rust-lang/rustc_codegen_cranelift#1648 end-to-end. r? bjorn3
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☔ The latest upstream changes (possibly 9446d0d) made this pull request unmergeable. Please resolve the merge conflicts. |
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| // <https://github.com/llvm/llvm-project/blob/llvmorg-22.1.3/llvm/lib/MC/MCSectionMachO.cpp#L23-L91> | ||
| // <https://github.com/llvm/llvm-project/blob/llvmorg-22.1.3/llvm/include/llvm/BinaryFormat/MachO.h#L120-L223> | ||
| const MACHO_SECTION_TYPES: &[(&str, u32)] = &[ | ||
| ("regular", object::macho::S_REGULAR), |
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Maybe use object::macho? Or even put those two tables in an inline submodule with use object::macho::*?
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I updated Cranelift earlier today, so it should work after a rebase. |
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@madsmtm did you intend to work on this further or do you want me to pick it up? |
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Mach-O sections have a 32-bit "flags" parameter, which contains 8 bits for a "section type", and 24 bits for "attributes". These can be controlled with
#[link_section = ...]like so:The default section type is "regular" (
S_REGULAR).This PR parses the section type names and attribute names understood by LLVM, and convert them to the corresponding Mach-O flags.
Fixes #1588.
Depends on bytecodealliance/wasmtime#13137.
Related to rust-lang/rust#155065, we could also put this parsing logic higher up, to rely less on LLVM / get diagnostics with spans for this on all backends?