llvm-project

cb180d50 - [cmake] FindLibXml2: keep user-provided LIBXML2_DEFINITIONS (#221294)

[cmake] FindLibXml2: keep user-provided LIBXML2_DEFINITIONS (#221294) LLVM's `FindLibXml2.cmake` (added in #166867) unconditionally does `set(LIBXML2_DEFINITIONS ${PC_LIBXML_CFLAGS_OTHER})` and puts `PC_LIBXML_CFLAGS_OTHER` on the imported targets. CMake's own `FindLibXml2` module only takes pkg-config's flags when the library it found is the one pkg-config describes; otherwise it keeps whatever `LIBXML2_DEFINITIONS` the user passed and exposes it through `INTERFACE_COMPILE_OPTIONS`. This matters when cross-compiling against a static libxml2 on Windows. Passing `-DLIBXML2_DEFINITIONS=-DLIBXML_STATIC -DLIBXML2_LIBRARIES=.../libxml2s.lib` worked with LLVM 22 (CMake's module): the define reached both the `xmlReadMemory` configure check and the consumers of `LibXml2::LibXml2`. With LLVM 23 it is silently dropped, `xmlexports.h` declares the API `__declspec(dllimport)`, the check fails to link against the static library and `LLVM_ENABLE_LIBXML2=FORCE_ON` aborts with `Failed to configure libxml2`. (pkg-config on the Linux host finds the host's libxml2, so `PC_LIBXML_CFLAGS_OTHER` is empty and unrelated to the library actually being used.) Mirror CMake's behaviour: keep the user's definitions unless pkg-config found the same library, and attach them to both `LibXml2::LibXml2` and `LibXml2::LibXml2Static`. Seen while building the Firefox clang 23 toolchains (x86_64 and aarch64 `-pc-windows-msvc`, cross-compiled from Linux with `LLVM_EXPORT_SYMBOLS_FOR_PLUGINS=ON`). --- **AI tool use disclosure** (per the [LLVM AI Tool Use Policy](https://llvm.org/docs/AIToolPolicy.html)): this change was developed with Claude Code assisting in the analysis and drafting. The root cause was established against real 23.1.0 binaries; this cmake change itself has so far only been verified to apply to 23.1.0 and main and by code reading, while Firefox's CI validated the equivalent workaround of passing -DLIBXML_STATIC via the compiler flags. The author reviewed the change and is accountable for and able to answer questions about it. Commits carry an `Assisted-by:` trailer.