c++03 ci

.github/workflows/linux-x64-cpu-gcc.yml

@@ -31,6 +31,17 @@ jobs:
     - name: test
       run: cd build && ctest --output-on-failure -j 2
 
+  linux-gcc-cpp03:
+    runs-on: ubuntu-16.04
+    steps:
+    - uses: actions/checkout@v2
+    - name: configure
+      run: mkdir build && cd build && cmake -DCMAKE_TOOLCHAIN_FILE=../toolchains/host.gcc-c++03.toolchain.cmake -DNCNN_BUILD_TESTS=ON -DNCNN_BUILD_TOOLS=OFF -DNCNN_BUILD_EXAMPLES=OFF ..
+    - name: build
+      run: cmake --build build -j 2
+    - name: test
+      run: cd build && ctest --output-on-failure -j 2
+
   linux-gcc-nostdio-nostring:
     runs-on: ubuntu-16.04
     steps:

toolchains/host.gcc-c++03.toolchain.cmake

@@ -0,0 +1,16 @@
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR x86)
+
+set(CMAKE_C_COMPILER "gcc")
+set(CMAKE_CXX_COMPILER "g++")
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+
+set(CMAKE_C_FLAGS "-ansi")
+set(CMAKE_CXX_FLAGS "-std=c++03")
+
+# cache flags
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}" CACHE STRING "c flags")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}" CACHE STRING "c++ flags")