Set required C++ version

[AMDmi3]

6e9c007 introduced a regression. The code requires c++17 (not c++11) and it's not yet default everywhere.

[AMDmi3]

On a second though, the fix may be incorrect. The c++17 requirement in fact comes from abseil which is protobuf dependency. Here's the failure:

/usr/local/libexec/ccache/c++ -DPROTOBUF_USE_DLLS -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -I/work/usr/ports/astro/libosmpbf/work/OSM-binary-1.5.1/include -I/work/usr/ports/astro/libosmpbf/work/.build -isystem /usr/local/include -O2 -pipe -fstack-protector-strong -fno-strict-aliasi
ng -O2 -pipe -fstack-protector-strong -fno-strict-aliasing   -DNDEBUG -std=gnu++14 -pthread -MD -MT tools/CMakeFiles/osmpbf-outline.dir/osmpbf-outline.cpp.o -MF tools/CMakeFiles/osmpbf-outline.dir/osmpbf-outline.cpp.o.d -o tools/CMakeFiles/osmpbf-outline.dir/osmpbf-outline.cpp.o -c /
work/usr/ports/astro/libosmpbf/work/OSM-binary-1.5.1/tools/osmpbf-outline.cpp
In file included from /work/usr/ports/astro/libosmpbf/work/OSM-binary-1.5.1/tools/osmpbf-outline.cpp:24:
In file included from /work/usr/ports/astro/libosmpbf/work/OSM-binary-1.5.1/include/osmpbf/osmpbf.h:16:
In file included from /work/usr/ports/astro/libosmpbf/work/.build/osmpbf/fileformat.pb.h:24:
In file included from /usr/local/include/google/protobuf/io/coded_stream.h:134:
In file included from /usr/local/include/absl/strings/cord.h:78:
In file included from /usr/local/include/absl/container/inlined_vector.h:53:
In file included from /usr/local/include/absl/container/internal/inlined_vector.h:30:
In file included from /usr/local/include/absl/container/internal/compressed_tuple.h:40:
/usr/local/include/absl/utility/utility.h:164:12: error: no member named 'in_place_t' in namespace 'std'
using std::in_place_t;
      ~~~~~^

As you can see, there's -std=gnu++14 (not sure where it comes from though) and std::in_place_t is only available since c++17.

The patch proposed does not solve the problem, but this one does:

--- osmpbf/CMakeLists.txt.orig	2024-03-11 08:26:22 UTC
+++ osmpbf/CMakeLists.txt
@@ -1,13 +1,13 @@ add_library(osmpbf STATIC ${CPPS})
 protobuf_generate_cpp(CPPS HS fileformat.proto osmformat.proto)
 
 add_library(osmpbf STATIC ${CPPS})
-target_compile_features(osmpbf PUBLIC cxx_std_11)
+target_compile_features(osmpbf PUBLIC cxx_std_17)
 target_link_libraries(osmpbf PRIVATE protobuf::libprotobuf)
 target_include_directories(osmpbf SYSTEM PUBLIC ${Protobuf_INCLUDE_DIRS})
 install(TARGETS osmpbf ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 
 add_library(osmpbf_shared SHARED ${CPPS})
-target_compile_features(osmpbf_shared PUBLIC cxx_std_11)
+target_compile_features(osmpbf_shared PUBLIC cxx_std_17)
 target_link_libraries(osmpbf_shared PRIVATE protobuf::libprotobuf)
 target_include_directories(osmpbf_shared SYSTEM PUBLIC ${Protobuf_INCLUDE_DIRS})
 set_target_properties(osmpbf_shared PROPERTIES OUTPUT_NAME osmpbf

[joto]

Hmpf. We don't require C++17 and we don't want to require it. So both your solutions don't work. CMake should be able to figure out which C++ version to require based on all the dependencies, that's its job. That's what we have been trying to get it to do in #76. In your case it seems CMake chooses -std=gnu++14 for some reason, but it did work for some people in #76. :-(