cbindgen: Pass Rust target-triple to cbindgen

RELEASES.md

@@ -12,16 +12,23 @@
 - Support using the `$<CONFIG>` generator expression in `OUTPUT_DIRECTORY`. [#459]
 - If `corrosion_link_libraries()` is called on a Rust static library target, then
   `target_link_libraries()` is called to propogate the dependencies to C/C++ consumers.
-  Previously a warning was emitted in this case and the arguments ignored.
+  Previously a warning was emitted in this case and the arguments ignored. [#506]
+- `corrosion_experimental_cbindgen()` can now be called multiple times on the same Rust target,
+  as long as the output header name differs. This may be useful to generate separate C and C++
+  bindings. [#507]
 
 ### Fixes
 
 - Combine `-framework` flags on macos to avoid linker deduplication errors [#455]
 - Set the `AR_<triple>` variable for `cc-rs` (except for msvc targets) [#456]
+- `corrosion_experimental_cbindgen()` now forwards the Rust target-triple (e.g. `aarch64-unknown-linux-gnu`)
+  to cbindgen via the `TARGET` environment variable. The `hostbuild` property is considered. [#507]
 
 [#459]: https://github.com/corrosion-rs/corrosion/pull/459
 [#456]: https://github.com/corrosion-rs/corrosion/pull/456
 [#455]: https://github.com/corrosion-rs/corrosion/pull/455
+[#506]: https://github.com/corrosion-rs/corrosion/pull/506
+[#507]: https://github.com/corrosion-rs/corrosion/pull/507
 
 # v0.4.7 (2024-01-19)
 

cmake/Corrosion.cmake

@@ -1539,10 +1539,13 @@ between multiple invocations of this function.
 ANCHOR_END: corrosion_cbindgen
 #]=======================================================================]
 function(corrosion_experimental_cbindgen)
-    # Todo:
-    # - set the target-triple via the TARGET env variable based on the target triple for the rust crate.
     set(OPTIONS "")
-    set(ONE_VALUE_KEYWORDS TARGET CARGO_PACKAGE MANIFEST_DIRECTORY HEADER_NAME CBINDGEN_VERSION)
+    set(ONE_VALUE_KEYWORDS
+            TARGET
+            CARGO_PACKAGE
+            MANIFEST_DIRECTORY
+            HEADER_NAME
+            CBINDGEN_VERSION)
     set(MULTI_VALUE_KEYWORDS "FLAGS")
     cmake_parse_arguments(PARSE_ARGV 0 CCN "${OPTIONS}" "${ONE_VALUE_KEYWORDS}" "${MULTI_VALUE_KEYWORDS}")
 
@@ -1557,6 +1560,10 @@ function(corrosion_experimental_cbindgen)
     set(rust_target "${CCN_TARGET}")
     unset(package_manifest_dir)
 
+
+    set(hostbuild_override "$<BOOL:$<TARGET_PROPERTY:${rust_target},${_CORR_PROP_HOST_BUILD}>>")
+    set(cbindgen_target_triple "$<IF:${hostbuild_override},${_CORROSION_RUST_CARGO_HOST_TARGET},${_CORROSION_RUST_CARGO_TARGET}>")
+
     if(TARGET "${rust_target}")
         get_target_property(package_manifest_path "${rust_target}" INTERFACE_COR_PACKAGE_MANIFEST_PATH)
         if(NOT EXISTS "${package_manifest_path}")
@@ -1653,7 +1660,9 @@ function(corrosion_experimental_cbindgen)
         OUTPUT
         "${generated_header}"
         COMMAND
-        "${cbindgen}"
+        "${CMAKE_COMMAND}" -E env
+            TARGET="${cbindgen_target_triple}"
+            "${cbindgen}"
                     --output "${generated_header}"
                     --crate "${rust_cargo_package}"
                     ${depfile_cbindgen_arg}
@@ -1672,11 +1681,19 @@ function(corrosion_experimental_cbindgen)
         )
     endif()
 
-    add_custom_target(_corrosion_cbindgen_${rust_target}_bindings
-        DEPENDS "${generated_header}"
-        COMMENT "Generate cbindgen bindings for package ${rust_cargo_package}"
+    if(NOT TARGET "_corrosion_cbindgen_${rust_target}_bindings")
+        add_custom_target(_corrosion_cbindgen_${rust_target}_bindings
+                COMMENT "Generate cbindgen bindings for package ${rust_cargo_package}"
+        )
+    endif()
+    # Users might want to call cbindgen multiple times, e.g. to generate separate C++ and C header files.
+    string(MAKE_C_IDENTIFIER "${output_header_name}" header_identifier )
+    add_custom_target("_corrosion_cbindgen_${rust_target}_bindings_${header_identifier}"
+            DEPENDS "${generated_header}"
+            COMMENT "Generate ${generated_header} for ${rust_target}"
     )
-    add_dependencies(${rust_target} _corrosion_cbindgen_${rust_target}_bindings)
+    add_dependencies("_corrosion_cbindgen_${rust_target}_bindings" "_corrosion_cbindgen_${rust_target}_bindings_${header_identifier}")
+    add_dependencies(${rust_target} "_corrosion_cbindgen_${rust_target}_bindings")
 endfunction()
 
 # Parse the version of a Rust package from it's package manifest (Cargo.toml)