replace boost::variant by std::variant

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 ### Changed
 
+- `boost::variant` has been replaced by `std::variant` and Boost is no longer needed as a dependency
 - If no explicit choice is made via `CMAKE_POSITION_INDEPENDENT_CODE`, the client library defaults to being built as position independent code
 
 [Unreleased]: https://gitlab.version.fz-juelich.de/SIONlib/SIONfwd/-/compare/v1.0.0...main

CMakeLists.txt

@@ -18,7 +18,6 @@ set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED TRUE)
 set(CMAKE_C_EXTENSIONS FALSE)
 
-find_package(Boost 1.69 REQUIRED)
 find_package(MPI 3.0 REQUIRED)
 
 find_program(CLANG_TIDY_EXE NAMES "clang-tidy" DOC "Path to clang-tidy executable")
@@ -49,7 +48,6 @@ if(NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
 endif()
 
 add_executable(sionfwd-server src/server.cxx)
-target_link_libraries(sionfwd-server PRIVATE Boost::boost)
 target_link_libraries(sionfwd-server PRIVATE MPI::MPI_CXX)
 
 add_executable(sionfwd-test-client src/test-client.c)

README.md

@@ -9,7 +9,6 @@ It contains a C++ server and a C client library.
 - C++ compiler with support for C++17
 - CMake 3.12 or newer
 - MPI 3.0 or newer
-- Boost 1.69 or newer
 
 ## Installation
 

cmake/SIONfwdConfig.cmake

 include(CMakeFindDependencyMacro)
 find_dependency(MPI 3.0)
-find_dependency(Boost 1.69)
 include("${CMAKE_CURRENT_LIST_DIR}/SIONfwdTargets.cmake")

src/server.cxx

@@ -11,10 +11,9 @@
 #include <sys/types.h>
 #include <sys/uio.h>
 #include <unistd.h>
+#include <variant>
 #include <vector>
 
-#include <boost/variant.hpp>
-
 #include <mpi.h>
 
 static bool debug = false;
@@ -214,7 +213,7 @@ private:
 
 struct Unknown {};
 
-using Message = boost::variant<
+using Message = std::variant<
   Shutdown,
   Hello,
   Disconnect,
@@ -228,11 +227,6 @@ using Message = boost::variant<
   Unknown
 >;
 
-template<typename T, typename... Us>
-bool holds_alternative(const boost::variant<Us...>& v) {
-  return boost::get<T>(&v) != nullptr;
-}
-
 struct Communicator {
   explicit Communicator(MPI_Comm comm) noexcept : comm_{comm} {}
 
@@ -460,7 +454,7 @@ struct CommunicatorReceiver {
     bool go_on;
     do {
       Message message{communicator_.receive()};
-      go_on = boost::apply_visitor(MessageVisitor{communicator_}, std::move(message));
+      go_on = std::visit(MessageVisitor{communicator_}, std::move(message));
     } while (go_on);
   }
 
@@ -521,8 +515,8 @@ struct PortAcceptor {
       }
       Communicator client{port_.accept()};
       Message message{client.receive()};
-      if (holds_alternative<Shutdown>(message)) { break; }
-      if (!holds_alternative<Hello>(message)) {
+      if (std::holds_alternative<Shutdown>(message)) { break; }
+      if (!std::holds_alternative<Hello>(message)) {
         throw std::runtime_error{"unexpected message type"};
       }
       CommunicatorReceiver{std::move(client)}();