fix: clang_macro_fallback with header_contents() and implicit --target#3353
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zRedShift wants to merge 3 commits intorust-lang:mainfrom
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fix: clang_macro_fallback with header_contents() and implicit --target#3353zRedShift wants to merge 3 commits intorust-lang:mainfrom
clang_macro_fallback with header_contents() and implicit --target#3353zRedShift wants to merge 3 commits intorust-lang:mainfrom
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Fixes rust-lang#3351 clang_macro_fallback() silently produced no output when headers were provided via header_contents() instead of header(). This happened because try_ensure_fallback_translation_unit() only looked at input_headers (populated by .header()), returning None when it was empty. Fix: materialize input_header_contents to disk in the fallback build directory so clang can consume them for PCH compilation. Both input_headers and input_header_contents are now included in the fallback PCH, so mixed .header() + .header_contents() setups work. The materialized paths are sanitized (roots stripped, ".." resolved) to prevent escaping the build directory, and tracked in FallbackTranslationUnit for cleanup on drop. Also stop using std::mem::take on input_header_contents in Builder::generate(), preserving the data for the fallback TU (and fixing a pre-existing bug where serialize_items in codegen couldn't see header contents). Also store the original user-provided name in input_header_contents at header_contents() time so the fallback can reconstruct relative paths without depending on the current working directory.
Fixes rust-lang#3352 When bindgen infers the target triple from the Rust target (i.e., no explicit --target in clang_args), it inserts --target= into clang_args at Bindings::generate() time. However, fallback_clang_args was already populated from clang_args earlier in Builder::generate(), before this insertion. This meant the fallback translation unit used for clang_macro_fallback would use the host architecture instead of the target architecture. For cross-compilation, this caused sizeof-dependent macros (e.g., ioctl constants using _IOR/_IOW) to evaluate with the host's struct layouts instead of the target's, producing silently wrong values. Fix: when inserting the inferred target into clang_args, also insert it into fallback_clang_args.
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clang 9's clang_Cursor_Evaluate returns CXEval_UnExposed instead of CXEval_Int for macro-expanded expressions loaded through a PCH, so clang_macro_fallback produces no constants on that version. The existing header-based fallback tests already handle this with clang-9-specific empty expectation files; apply the same pattern to the new inline tests by skipping when libclang 9 is detected.
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Summary
Fixes #3351 and #3352.
Two bugs in
clang_macro_fallback:header_contents()silently skipped (clang_macro_fallback()silently skipped when usingheader_contents()#3351):try_ensure_fallback_translation_unit()only checkedinput_headers(populated by.header()). When headers were provided via.header_contents(),input_headerswas empty, the fallback returnedNone, and every macro that needed it was silently dropped. Additionally,Builder::generate()usedstd::mem::take()oninput_header_contents, so even if the fallback checked it, the data was already gone.Implicit
--targetnot propagated (clang_macro_fallbackdoesn't propagate implicit--targetto fallback translation unit #3352):fallback_clang_argswas populated fromclang_argsinBuilder::generate()beforeBindings::generate()inserted the inferred--target=triple. Cross-compilation would evaluatesizeof-dependent macros (e.g. ioctl constants via_IOR/_IOW) with the host's struct layouts instead of the target's.