require c++17 for building with new protobuf (#4947)

nihui · web-flow · commit 39721eeb9400 · 2023-08-16T11:48:56.000+08:00
diff --git a/tools/caffe/CMakeLists.txt b/tools/caffe/CMakeLists.txt
@@ -2,6 +2,10 @@
 find_package(Protobuf)
 
 if(PROTOBUF_FOUND)
+    if(DEFINED Protobuf_VERSION AND Protobuf_VERSION VERSION_GREATER_EQUAL 3.22)
+        set(CMAKE_CXX_STANDARD 17)
+    endif()
+
     protobuf_generate_cpp(CAFFE_PROTO_SRCS CAFFE_PROTO_HDRS caffe.proto)
     add_executable(caffe2ncnn caffe2ncnn.cpp ${CAFFE_PROTO_SRCS} ${CAFFE_PROTO_HDRS})
     target_include_directories(caffe2ncnn
diff --git a/tools/onnx/CMakeLists.txt b/tools/onnx/CMakeLists.txt
@@ -2,6 +2,10 @@
 find_package(Protobuf)
 
 if(PROTOBUF_FOUND)
+    if(DEFINED Protobuf_VERSION AND Protobuf_VERSION VERSION_GREATER_EQUAL 3.22)
+        set(CMAKE_CXX_STANDARD 17)
+    endif()
+
     protobuf_generate_cpp(ONNX_PROTO_SRCS ONNX_PROTO_HDRS onnx.proto)
     add_executable(onnx2ncnn onnx2ncnn.cpp ${ONNX_PROTO_SRCS} ${ONNX_PROTO_HDRS})
     target_include_directories(onnx2ncnn
