⚗️ try official GCC containers

.github/workflows/ubuntu.yml

@@ -90,6 +90,21 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           path-to-lcov: ${{ github.workspace }}/build/json.info.filtered.noexcept
 
+  ci_test_compilers_gcc:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: ['7.5.0', '8.5.0']
+    container: gcc:${{ matrix.compiler }}
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install CMake
+        run: sudo apt-get update ; sudo apt-get install -y cmake
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_test_compiler_default
+
   ci_test_compilers:
     runs-on: ubuntu-latest
     container: ghcr.io/nlohmann/json-ci:v2.4.0

cmake/ci.cmake

@@ -929,6 +929,17 @@ foreach(COMPILER g++-4.8 g++-4.9 g++-5 g++-6 g++-7 g++-8 g++-9 g++-10 g++-11 cla
     unset(COMPILER_TOOL CACHE)
 endforeach()
 
+add_custom_target(ci_test_compiler_default
+    COMMAND ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug
+        -DJSON_BuildTests=ON -DJSON_FastTests=ON
+        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_compiler_default
+        ${ADDITIONAL_FLAGS}
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_compiler_default --parallel ${N}
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_default && ${CMAKE_CTEST_COMMAND} --parallel ${N} --exclude-regex "test-unicode" --output-on-failure
+    COMMENT "Compile and test with default C++ compiler"
+)
+
 ###############################################################################
 # CUDA example
 ###############################################################################