run cargo from CMake, remove hardcoded target from .cargo/config (#5)

* cmake: run cargo build from idf.py build

.cargo/config

@@ -1,6 +1,3 @@
-[build]
-target = "xtensa-esp32-none-elf"
-
-[unstable]
-build-std = ["std", "panic_abort"]
-build-std-features = ["panic_immediate_abort"]
+[unstable]
+build-std = ["std", "panic_abort"]
+build-std-features = ["panic_immediate_abort"]

.gitignore

@@ -3,6 +3,7 @@ build/
 target/
 
 sdkconfig.old
+sdkconfig
 debug/
 target/
 Cargo.lock

README.md

@@ -20,50 +20,6 @@ Install the RISCV target for Rust:
 rustup target add riscv32i-unknown-none-elf
 ```
 
-## Build Rust library
-
-This will eventually be folded into the main CMake build, but for now, build the library separately.
-
-### ESP32 or ESP32-S2
-
-To build the Rust library, run:
-
-```sh
-cd rustlib
-xargo build --release
-cd ..
-```
-
-Build with manual configuration of the target:
-
-```sh
-export RUSTC=/usr/local/xtensa/rust/bin/rustc
-export XARGO_RUST_SRC=/usr/local/xtensa/rust/library
-cd rustlib
-xargo build --release --target=xtensa-esp32-none-elf
-cd ..
-```
-
-### ESP32-C3
-
-To build the Rust library, run:
-
-```sh
-cd rustlib
-cargo build --release
-cd ..
-```
-
-Build with manual configuration of the target:
-
-```sh
-unset RUSTC
-unset XARGO_RUST_SRC
-cd rustlib
-cargo build --release --target=riscv32i-unknown-none-elf
-cd ..
-```
-
 ## Configure
 
 First ensure that the environment variables for the ESP32 SDK are properly set up. If you have followed the instructions in the Getting Started guide, activate the environment with the `get_idf` alias:
@@ -103,6 +59,8 @@ Build the project by running:
 idf.py build
 ```
 
+This also runs Cargo internally, building a static library out of Rust code.
+
 ## Flash
 
 Flash the compiled binary by running:

docs/rust-on-xtensa-installation-aarch64-apple-darwin.md

@@ -33,9 +33,7 @@ export PATH="`pwd`/xtensa-esp32-elf-clang/bin/:$PATH"
 
 wget --continue https://github.com/espressif/rust-esp32-example/archive/refs/heads/main.zip
 unzip main.zip
-cd rust-esp32-example-main/rustlib
-cargo build --release
-cd ..
+cd rust-esp32-example-main
 idf.py build
 ```
 

docs/rust-on-xtensa-installation-x86_64-apple-darwin.md

@@ -31,11 +31,9 @@ wget https://dl.espressif.com/dl/idf-rust/dist/x86_64-apple-darwin/xtensa-esp32-
 tar xf xtensa-esp32-elf-llvm11_0_0-x86_64-apple-darwin.tar.xz
 export PATH="`pwd`/xtensa-esp32-elf-clang/bin/:$PATH"
 
-wget https://dl.espressif.com/dl/idf-rust/rust-esp32-example-0.2.tar.gz
-tar xvzf rust-esp32-example-0.2.tar.gz
-cd rust-esp32-example/rustlib
-cargo build --release
-cd ..
+wget --continue https://github.com/espressif/rust-esp32-example/archive/refs/heads/main.zip
+unzip main.zip
+cd rust-esp32-example-main
 idf.py build
 ```
 

docs/rust-on-xtensa-installation-x86_64-pc-windows-msvc.md

@@ -48,8 +48,6 @@ $env:PATH="${ClangPatchPath};$env:PATH"
 
 Invoke-WebRequest https://github.com/espressif/rust-esp32-example/archive/refs/heads/main.zip -OutFile rust-esp32-example.zip
 7z x rust-esp32-example.zip
-cd rust-esp32-example-main/rustlib
-cargo build --release
-cd ..
+cd rust-esp32-example-main
 idf.py build
 ```

docs/rust-on-xtensa-installation-x86_64-unknown-linux-gnu.md

@@ -39,11 +39,8 @@ wget https://dl.espressif.com/dl/idf-rust/dist/x86_64-unknown-linux-gnu/llvm-pat
 tar xzf llvm-patch-0.1.x86_64-unknown-linux-gnu.tar.gz
 export PATH="`pwd`/llvm-patch/bin/:$PATH"
 
-wget https://dl.espressif.com/dl/idf-rust/rust-esp32-example-0.2.tar.gz
-tar xvzf rust-esp32-example-0.2.tar.gz
-cd rust-esp32-example/rustlib
-cargo build --release
-cd ..
+wget --continue https://github.com/espressif/rust-esp32-example/archive/refs/heads/main.zip
+unzip main.zip
+cd rust-esp32-example-main
 idf.py build
 ```
-

main/CMakeLists.txt

@@ -1,16 +1,44 @@
 idf_component_register(SRCS "main.c"
                     INCLUDE_DIRS "")
 
-set(CargoBuildType "release")
-
-# Import the Rust library.
-if((${IDF_TARGET} MATCHES "esp32") OR (${IDF_TARGET} MATCHES "esp32s2"))
-    set(ToolchainTarget "xtensa-esp32-none-elf")
-elseif(${IDF_TARGET} MATCHES "esp32c3")
-    set(ToolchainTarget "riscv32i-unknown-none-elf")
+set(CARGO_BUILD_TYPE "release")
+set(CARGO_BUILD_ARG "--release")
+if(CONFIG_IDF_TARGET_ARCH_RISCV)
+    set(CARGO_TARGET "riscv32i-unknown-elf")
+elseif(CONFIG_IDF_TARGET_ARCH_XTENSA)
+    set(CARGO_TARGET "xtensa-${CONFIG_IDF_TARGET}-none-elf")
 endif()
 
-add_prebuilt_library(rustlib "../rustlib/target/${ToolchainTarget}/${CargoBuildType}/librustlib.a")
+set(RUST_PROJECT_DIR "${CMAKE_CURRENT_LIST_DIR}/../rustlib")
+set(RUST_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/rustlib")
+set(RUST_STATIC_LIBRARY "${RUST_BUILD_DIR}/${CARGO_TARGET}/${CARGO_BUILD_TYPE}/librustlib.a")
+
+ExternalProject_Add(
+    rustlib_project
+    PREFIX "${RUST_PROJECT_DIR}"
+    BUILD_COMMAND ${CMAKE_COMMAND} -E env
+        CARGO_BUILD_TARGET=${CARGO_TARGET}
+        CARGO_BUILD_TARGET_DIR=${RUST_BUILD_DIR}
+        cargo build ${CARGO_BUILD_ARG}
+    DOWNLOAD_COMMAND ""
+    CONFIGURE_COMMAND ""
+    INSTALL_COMMAND ""
+    BUILD_ALWAYS TRUE
+    BUILD_DIR "${RUST_BUILD_DIR}"
+    INSTALL_DIR "${RUST_BUILD_DIR}"
+    STAMP_DIR "${RUST_BUILD_DIR}/stamp"
+    TMP_DIR "${RUST_BUILD_DIR}/tmp"
+    DOWNLOAD_DIR "${RUST_BUILD_DIR}"
+    SOURCE_DIR "${RUST_PROJECT_DIR}"
+    BUILD_BYPRODUCTS "${RUST_STATIC_LIBRARY}"
+)
+
+# this adds "rustlib" static library target.
+# PRIV_REQUIRES tells CMake that librustlib.a itself depends on libmain.a.
+add_prebuilt_library(rustlib "${RUST_STATIC_LIBRARY}" PRIV_REQUIRES main)
+
+# rustlib will be produced by building rustlib_project target
+add_dependencies(rustlib rustlib_project)
 
 # 'main' calls a function from the library, so link it to 'main'
 target_link_libraries(${COMPONENT_LIB} PRIVATE rustlib)