feat: add mcpp build support and switch Linux CI to mcpp

Add `mcpp.toml` at the project root so mcpp can build the library
natively, dropping the hand-written `mcpp = {}` workaround in
mcpp-index. The Linux CI job now bootstraps mcpp via xlings and runs
`mcpp build` + `mcpp test`; macOS and Windows continue to use xmake
since mcpp's support on those platforms is still WIP.

Tests no longer define their own `main()` — `mcpp test` always links
`gtest_main`, so `tests/xmake.lua` is updated to request gtest with
`main = true` to keep both build systems consistent.

README adds a mcpp section under "构建" and "集成到构建工具".

Author: Sunrisepeak

.github/workflows/ci.yml

@@ -6,53 +6,72 @@ on:
   pull_request:
     branches: [main, master]
 
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build-linux:
-    runs-on: ubuntu-latest
+    name: build + test (linux x86_64, mcpp)
+    runs-on: ubuntu-24.04
+    timeout-minutes: 30
+    env:
+      MCPP_HOME: /home/runner/.mcpp
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
 
-      - name: Setup xmake
-        uses: xmake-io/github-action-setup-xmake@v1
+      # mcpp's sandbox (musl-gcc + ninja + binutils) is multi-hundred-MB;
+      # key on mcpp.toml so toolchain changes refresh the cache.
+      - name: Cache mcpp sandbox
+        uses: actions/cache@v4
         with:
-          xmake-version: latest
-          package-cache: true
+          path: ~/.mcpp
+          key: mcpp-sandbox-${{ runner.os }}-${{ hashFiles('mcpp.toml') }}
+          restore-keys: |
+            mcpp-sandbox-${{ runner.os }}-
 
-      - name: Install dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y build-essential
-
-      - name: Install Xlings
-        run: curl -fsSL https://d2learn.org/xlings-install.sh | bash
-
-      - name: Install GCC 15.1 with Xlings
+      - name: Cache xlings
+        uses: actions/cache@v4
+        with:
+          path: ~/.xlings
+          key: xlings-${{ runner.os }}
+          restore-keys: |
+            xlings-${{ runner.os }}-
+
+      - name: Bootstrap mcpp via xlings
+        env:
+          XLINGS_NON_INTERACTIVE: '1'
         run: |
-          export PATH=/home/xlings/.xlings_data/bin:$PATH
-          xlings install gcc@15.1 -y
+          if [ ! -x "$HOME/.xlings/subos/default/bin/xlings" ]; then
+            curl -fsSL https://d2learn.org/xlings-install.sh | bash
+          fi
+          export PATH="$HOME/.xlings/subos/default/bin:$PATH"
+          xlings --version
+          xlings install mcpp -y
+          mcpp --version
+          echo "$HOME/.xlings/subos/default/bin" >> "$GITHUB_PATH"
+
+      - name: Cache target/ (build artifacts + BMIs)
+        uses: actions/cache@v4
+        with:
+          path: target
+          key: mcpp-target-${{ runner.os }}-${{ hashFiles('src/**', 'tests/**', 'mcpp.toml') }}
+          restore-keys: |
+            mcpp-target-${{ runner.os }}-
 
       - name: Build
-        run: |
-          export PATH=/home/xlings/.xlings_data/bin:$PATH
-          xmake -y -vv
+        run: mcpp build
 
       - name: Test
-        run: |
-          export PATH=/home/xlings/.xlings_data/bin:$PATH
-          xmake run cmdline_test
-
-      - name: Run examples (smoke)
-        run: |
-          export PATH=/home/xlings/.xlings_data/bin:$PATH
-          xmake run with_dispatch -- add python 3.12
-          xmake run with_dispatch -- remove foo
+        run: mcpp test
 
+  # mcpp is Linux-x86_64 first; macOS/Windows support is still WIP, so the
+  # cross-platform xmake build keeps coverage for those targets.
   build-macos:
+    name: build (macOS, xmake)
     runs-on: macos-latest
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
 
       - name: Setup xmake
         uses: xmake-io/github-action-setup-xmake@v1
@@ -69,10 +88,10 @@ jobs:
           xmake -y -vv
 
   build-windows:
+    name: build + test (Windows, xmake)
     runs-on: windows-latest
     steps:
-      - name: Checkout
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
 
       - name: Setup xmake
         uses: xmake-io/github-action-setup-xmake@v1

.gitignore

@@ -1,2 +1,3 @@
 .xmake
 build
+target

README.md

@@ -76,12 +76,21 @@ auto r3 = app.parse_from("myapp remove x --yes");
 
 ## 构建
 
+**使用 xmake**
+
 ```shell
 xmake                       # 构建库
 xmake run basic             # 运行基础示例
 xmake -y run cmdline_test   # 运行测试（自动安装 gtest）
 ```
 
+**使用 mcpp**
+
+```shell
+mcpp build                  # 构建库
+mcpp test                   # 运行 tests/ 下的测试
+```
+
 ## 集成到构建工具
 
 ### xmake
@@ -101,6 +110,17 @@ target("mytool")
     set_policy("build.c++.modules", true)
 ```
 
+### mcpp
+
+在项目的 `mcpp.toml` 中声明依赖：
+
+```toml
+[dependencies]
+"mcpplibs.cmdline" = "^0.0.2"
+```
+
+然后在源码中 `import mcpplibs.cmdline;` 即可使用。
+
 ## 相关链接
 
 - [社区官网](https://mcpp.d2learn.org)

mcpp.toml

@@ -0,0 +1,16 @@
+[package]
+name        = "mcpplibs.cmdline"
+version     = "0.0.2"
+description = "A simple command-line parsing library/framework for modern C++"
+license     = "Apache-2.0"
+authors     = ["mcpplibs"]
+repo        = "https://github.com/mcpplibs/cmdline"
+
+# Library target — exposes module `mcpplibs.cmdline` to dependents.
+# Sources default to src/**/*.{cppm,cpp,cc,c}; tests/ and examples/ are
+# discovered separately (`mcpp test` / standalone builds).
+[targets.cmdline]
+kind = "lib"
+
+[dev-dependencies]
+gtest = "1.15.2"

tests/cmdline_test.cpp

@@ -3,11 +3,6 @@
 import std;
 import mcpplibs.cmdline;
 
-int main(int argc, char** argv) {
-    ::testing::InitGoogleTest(&argc, argv);
-    return RUN_ALL_TESTS();
-}
-
 using namespace mcpplibs::cmdline;
 
 // Build argv from program name + args for parse()

tests/xmake.lua

@@ -1,7 +1,7 @@
 add_rules("mode.debug", "mode.release")
 set_languages("c++23")
 
-add_requires("gtest")
+add_requires("gtest", { configs = { main = true } })
 
 target("cmdline_test")
     set_kind("binary")