ci: Add a cppcheck run to test C/C++ code.

Currently, `src` may return errors, but `extern` is only on warning
level.

Author: QuLogic

.github/workflows/reviewdog.yml

@@ -25,3 +25,25 @@ jobs:
           REVIEWDOG_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           flake8 | reviewdog -f=pep8 -name=flake8 -reporter=github-check
+
+  cppcheck:
+    name: run-cppcheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install linters
+        run: |
+          sudo apt update
+          sudo apt install -qq cppcheck
+
+      - name: Set up reviewdog
+        run: |
+          mkdir -p $HOME/bin && curl -sfL https://raw.githubusercontent.com/reviewdog/reviewdog/master/install.sh| sh -s -- -b $HOME/bin
+          echo ::add-path::$HOME/bin
+      - name: Run reviewdog
+        env:
+          REVIEWDOG_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          cppcheck --quiet --template="{file}:{line}:{column}: {id}: {message}" src/ |& reviewdog -f=pep8 -name=cppcheck -reporter=github-check
+          # cppcheck --quiet --template="{file}:{line}:{column}: {id}: {message}" extern/ |& reviewdog -f=pep8 -name=cppcheck -reporter=github-check -level=warning