Linking broken on Linux x86-64?

CMakeLists.txt と hello サブディレクトリから始め、次に生成された hello/CMakeFiles/hello.dir/link.txt を調べ、make VERBOSE=1 で再現します。Rust のコンパイルルールがオブジェクトを生成する一方で、リンクルールが変数をエコーするだけになる理由を追跡します。hello のビルドによって hello.rs.o だけでなくリンク済みの実行可能ファイルが生成されれば完了です。

The included example hello binary seems to be disabled. After enabling it...:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 52419eb..d033346 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,7 @@ set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
 enable_language(Rust)
 include(CMakeCargo)
 
+add_subdirectory(hello)
 add_subdirectory(hello_world)
 add_subdirectory(crates)

an object file is generated but no linked executable:

$ find build/hello
build/hello
build/hello/Makefile
build/hello/CMakeFiles
build/hello/CMakeFiles/hello.dir
build/hello/CMakeFiles/hello.dir/link.txt
build/hello/CMakeFiles/hello.dir/flags.make
build/hello/CMakeFiles/hello.dir/hello.rs.o
build/hello/CMakeFiles/hello.dir/depend.internal
build/hello/CMakeFiles/hello.dir/cmake_clean.cmake
build/hello/CMakeFiles/hello.dir/build.make
build/hello/CMakeFiles/hello.dir/DependInfo.cmake
build/hello/CMakeFiles/hello.dir/progress.make
build/hello/CMakeFiles/hello.dir/depend.make
build/hello/CMakeFiles/CMakeDirectoryInformation.cmake
build/hello/CMakeFiles/progress.marks
build/hello/cmake_install.cmake

It looks like the link step is just echoing some commands. Am I missing something?

CMakeRust/build/hello$ make VERBOSE=1
cd /home/jnewsome/src/CMakeRust/build && /usr/bin/cmake -H/home/jnewsome/src/CMakeRust -B/home/jnewsome/src/CMakeRust/build --check-build-system CMakeFiles/Makefile.cmake 0
cd /home/jnewsome/src/CMakeRust/build && /usr/bin/cmake -E cmake_progress_start /home/jnewsome/src/CMakeRust/build/CMakeFiles /home/jnewsome/src/CMakeRust/build/hello/CMakeFiles/progress.marks
cd /home/jnewsome/src/CMakeRust/build && make -f CMakeFiles/Makefile2 hello/all
make[1]: Entering directory '/home/jnewsome/src/CMakeRust/build'
make -f hello/CMakeFiles/hello.dir/build.make hello/CMakeFiles/hello.dir/depend
make[2]: Entering directory '/home/jnewsome/src/CMakeRust/build'
cd /home/jnewsome/src/CMakeRust/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/jnewsome/src/CMakeRust /home/jnewsome/src/CMakeRust/hello /home/jnewsome/src/CMakeRust/build /home/jnewsome/src/CMakeRust/build/hello /home/jnewsome/src/CMakeRust/build/hello/CMakeFiles/hello.dir/DependInfo.cmake --color=
make[2]: Leaving directory '/home/jnewsome/src/CMakeRust/build'
make -f hello/CMakeFiles/hello.dir/build.make hello/CMakeFiles/hello.dir/build
make[2]: Entering directory '/home/jnewsome/src/CMakeRust/build'
[ 50%] Building Rust object hello/CMakeFiles/hello.dir/hello.rs.o
cd /home/jnewsome/src/CMakeRust/build/hello && echo "CMAKE_Rust_COMPILE_OBJECT"
CMAKE_Rust_COMPILE_OBJECT
cd /home/jnewsome/src/CMakeRust/build/hello && echo "TARGET: hello TARGET_BASE: hello  OBJECT: CMakeFiles/hello.dir/hello.rs.o OBJECTS: OBJECTS OBJECT_DIR: CMakeFiles/hello.dir SOURCE: /home/jnewsome/src/CMakeRust/hello/hello.rs SOURCES: SOURCES  LINK_LIBRARIES: LINK_LIBRARIES FLAGS:  LINK_FLAGS: LINK_FLAGS "
TARGET: hello TARGET_BASE: hello  OBJECT: CMakeFiles/hello.dir/hello.rs.o OBJECTS: OBJECTS OBJECT_DIR: CMakeFiles/hello.dir SOURCE: /home/jnewsome/src/CMakeRust/hello/hello.rs SOURCES: SOURCES  LINK_LIBRARIES: LINK_LIBRARIES FLAGS:  LINK_FLAGS: LINK_FLAGS 
cd /home/jnewsome/src/CMakeRust/build/hello && /home/jnewsome/.cargo/bin/rustc --emit obj /home/jnewsome/src/CMakeRust/hello/hello.rs -o CMakeFiles/hello.dir/hello.rs.o
[100%] Linking Rust executable hello
cd /home/jnewsome/src/CMakeRust/build/hello && /usr/bin/cmake -E cmake_link_script CMakeFiles/hello.dir/link.txt --verbose=1
echo "CMAKE_Rust_LINK_EXECUTABLE"
CMAKE_Rust_LINK_EXECUTABLE
echo "TARGET: hello TARGET_BASE: hello  OBJECT: OBJECT OBJECTS: CMakeFiles/hello.dir/hello.rs.o OBJECT_DIR: CMakeFiles/hello.dir SOURCE: SOURCE SOURCES: SOURCES  LINK_LIBRARIES:  FLAGS:  LINK_FLAGS:  "
TARGET: hello TARGET_BASE: hello  OBJECT: OBJECT OBJECTS: CMakeFiles/hello.dir/hello.rs.o OBJECT_DIR: CMakeFiles/hello.dir SOURCE: SOURCE SOURCES: SOURCES  LINK_LIBRARIES:  FLAGS:  LINK_FLAGS:  
make[2]: Leaving directory '/home/jnewsome/src/CMakeRust/build'
[100%] Built target hello
make[1]: Leaving directory '/home/jnewsome/src/CMakeRust/build'
/usr/bin/cmake -E cmake_progress_start /home/jnewsome/src/CMakeRust/build/CMakeFiles 0