cmake: Use C++20 for MSVC, C++17 otherwise

make: Unix use C++17

CMakeLists.txt

@@ -12,7 +12,11 @@ message(STATUS "${PROJECT_NAME} version: ${PROJECT_VERSION}")
 #message(STATUS "minor: ${PROJECT_VERSION_MINOR}")
 #message(STATUS "patch: ${PROJECT_VERSION_PATCH}")
 
-set(CMAKE_CXX_STANDARD 20)
+if (MSVC)
+  set(CMAKE_CXX_STANDARD 20)
+else()
+  set(CMAKE_CXX_STANDARD 17)
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 

cmake/dependencies/CMakeLists.txt

@@ -304,4 +304,8 @@ if(BUILD_Cbc)
   message(CHECK_PASS "fetched")
 endif()
 
-set(CMAKE_CXX_STANDARD 20)
+if(MSVC)
+  set(CMAKE_CXX_STANDARD 20)
+else()
+  set(CMAKE_CXX_STANDARD 17)
+endif()

makefiles/Makefile.port.mk

@@ -65,7 +65,7 @@ ifneq ($(PLATFORM),WIN64)
     PLATFORM = LINUX
 
     CXX ?= g++
-    CCC = $(CXX) -fPIC -std=c++20 -fwrapv
+    CCC = $(CXX) -fPIC -std=c++17 -fwrapv
     L = so
 
     # This is needed to find libz.a
@@ -89,7 +89,7 @@ ifneq ($(PLATFORM),WIN64)
     LINK_FLAGS = \
   -Wl,-rpath,'$$ORIGIN' \
   -Wl,-rpath,'$$ORIGIN/../lib64' \
-  -Wl,-rpath,'$$ORIGIN/../lib'  
+  -Wl,-rpath,'$$ORIGIN/../lib'
     DISTRIBUTION_ID = $(shell lsb_release -i -s)
     DISTRIBUTION_NUMBER = $(shell lsb_release -r -s)
     DISTRIBUTION = $(DISTRIBUTION_ID)-$(DISTRIBUTION_NUMBER)
@@ -144,7 +144,7 @@ ifneq ($(PLATFORM),WIN64)
     MAC_MIN_VERSION = 10.15
     MAC_VERSION = -mmacosx-version-min=$(MAC_MIN_VERSION)
     CXX ?= clang++
-    CCC = $(CXX) -fPIC -std=c++20  $(MAC_VERSION) -stdlib=libc++
+    CCC = $(CXX) -fPIC -std=c++17  $(MAC_VERSION) -stdlib=libc++
     L = dylib
 
     ZLIB_LNK = -lz
@@ -194,7 +194,7 @@ ifneq ($(PLATFORM),WIN64)
     $(GLPK_LNK) \
     $(CPLEX_LNK) \
     $(XPRESS_LNK)
-  
+
   # language targets
   HAS_PYTHON ?= ON
   ifeq ($(PYTHON_VERSION),)

ortools/pdlp/CMakeLists.txt

@@ -9,15 +9,17 @@ list(FILTER _SRCS EXCLUDE REGEX ".*/test.*")
 
 set(NAME ${PROJECT_NAME}_pdlp)
 
+if(MSVC)
+  set(STANDARD 20)
+else()
+  set(STANDARD 17)
+endif()
+
 # Will be merge in libortools.so
 #add_library(${NAME} STATIC ${_SRCS})
 add_library(${NAME} OBJECT ${_SRCS})
 set_target_properties(${NAME} PROPERTIES
-if(WIN32)
-  CXX_STANDARD 20
-else()
-  CXX_STANDARD 17
-endif()
+  CXX_STANDARD ${STANDARD}
   CXX_STANDARD_REQUIRED ON
   CXX_EXTENSIONS OFF
   POSITION_INDEPENDENT_CODE ON

tools/Makefile.cc.java.dotnet

@@ -67,7 +67,7 @@ ifeq ($(SYSTEM),unix)
   CC_BIN := $(shell command -v $(CC) 2> /dev/null)
   CXX_BIN := $(shell command -v $(CXX) 2> /dev/null)
   DEBUG = -O4 -DNDEBUG
-  CXXFLAGS = -fPIC -std=c++20 $(DEBUG) \
+  CXXFLAGS = -fPIC -std=c++17 $(DEBUG) \
  -I$(INC_DIR) -I. $(ARCH) -Wno-deprecated \
  -DUSE_BOP -DUSE_GLOP -DUSE_PDLP \
  -DUSE_CBC -DUSE_CLP \