[R-package] Add version floor of R 3.5 (fixes #3212) (#3216)

CMakeLists.txt

@@ -11,7 +11,6 @@ OPTION(USE_OPENMP "Enable OpenMP" ON)
 OPTION(USE_GPU "Enable GPU-accelerated training" OFF)
 OPTION(USE_SWIG "Enable SWIG to generate Java API" OFF)
 OPTION(USE_HDFS "Enable HDFS support (EXPERIMENTAL)" OFF)
-OPTION(USE_R35 "Set to ON if your R version is not earlier than 3.5" OFF)
 OPTION(USE_TIMETAG "Set to ON to output time costs" OFF)
 OPTION(USE_DEBUG "Set to ON for Debug mode" OFF)
 OPTION(BUILD_STATIC_LIB "Build static library" OFF)
@@ -68,10 +67,6 @@ if(USE_SWIG)
   endif()
 endif(USE_SWIG)
 
-if(USE_R35)
-    ADD_DEFINITIONS(-DR_VER_ABOVE_35)
-endif(USE_R35)
-
 if(BUILD_FOR_R)
     list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake/modules")
     find_package(LibR REQUIRED)

R-package/DESCRIPTION

@@ -29,7 +29,7 @@ Suggests:
     processx,
     testthat
 Depends:
-    R (>= 3.4),
+    R (>= 3.5),
     R6 (>= 2.0)
 Imports:
     data.table (>= 1.9.6),

R-package/README.md

@@ -94,7 +94,7 @@ Windows users may need to run with administrator rights (either R or the command
 
 Set `use_gpu` to `TRUE` in `R-package/src/install.libs.R` to enable the build with GPU support. You will need to install Boost and OpenCL first: details for installation can be found in [Installation-Guide](https://github.com/microsoft/LightGBM/blob/master/docs/Installation-Guide.rst#build-gpu-version).
 
-If you are using a precompiled dll/lib locally, you can move the dll/lib into LightGBM root folder, modify `LightGBM/R-package/src/install.libs.R`'s 2nd line (change `use_precompile <- FALSE` to `use_precompile <- TRUE`), and install R-package as usual. **NOTE: If your R version is not smaller than 3.5.0, you should set `DUSE_R35=ON` in cmake options when build precompiled dll/lib**.
+If you are using a precompiled dll/lib locally, you can move the dll/lib into LightGBM root folder, modify `LightGBM/R-package/src/install.libs.R`'s 2nd line (change `use_precompile <- FALSE` to `use_precompile <- TRUE`), and install R-package as usual.
 
 When your package installation is done, you can check quickly if your LightGBM R-package is working by running the following:
 

R-package/src/R_object_helper.h

@@ -18,47 +18,29 @@
 // use .Internal(internalsID()) to uuid
 #define R_INTERNALS_UUID "2fdf6c18-697a-4ba7-b8ef-11c0d92f1327"
 
-#ifdef R_VER_ABOVE_35
-  #define NAMED_BITS 16
-  struct lgbm_sxpinfo {
-    unsigned int type : 5;
-    unsigned int scalar : 1;
-    unsigned int obj : 1;
-    unsigned int alt : 1;
-    unsigned int gp : 16;
-    unsigned int mark : 1;
-    unsigned int debug : 1;
-    unsigned int trace : 1;
-    unsigned int spare : 1;
-    unsigned int gcgen : 1;
-    unsigned int gccls : 3;
-    unsigned int named : NAMED_BITS;
-    unsigned int extra : 32 - NAMED_BITS;
-  };
-
-  // 64bit pointer
-  #if INTPTR_MAX == INT64_MAX
-    typedef int64_t xlen_t;
-  #else
-    typedef int xlen_t;
-  #endif
+#define NAMED_BITS 16
+struct lgbm_sxpinfo {
+  unsigned int type : 5;
+  unsigned int scalar : 1;
+  unsigned int obj : 1;
+  unsigned int alt : 1;
+  unsigned int gp : 16;
+  unsigned int mark : 1;
+  unsigned int debug : 1;
+  unsigned int trace : 1;
+  unsigned int spare : 1;
+  unsigned int gcgen : 1;
+  unsigned int gccls : 3;
+  unsigned int named : NAMED_BITS;
+  unsigned int extra : 32 - NAMED_BITS;
+};
 
+// 64bit pointer
+#if INTPTR_MAX == INT64_MAX
+  typedef int64_t xlen_t;
 #else
-  struct lgbm_sxpinfo {
-    unsigned int type : 5;
-    unsigned int obj : 1;
-    unsigned int named : 2;
-    unsigned int gp : 16;
-    unsigned int mark : 1;
-    unsigned int debug : 1;
-    unsigned int trace : 1;
-    unsigned int spare : 1;
-    unsigned int gcgen : 1;
-    unsigned int gccls : 3;
-  };
-
   typedef int xlen_t;
-#endif  // R_VER_ABOVE_35
+#endif
 
 struct lgbm_primsxp {
   int offset;

R-package/src/install.libs.R

@@ -170,9 +170,6 @@ if (!use_precompile) {
   if (use_gpu) {
     cmake_args <- c(cmake_args, "-DUSE_GPU=ON")
   }
-  if (R_ver >= 3.5) {
-    cmake_args <- c(cmake_args, "-DUSE_R35=ON")
-  }
   cmake_args <- c(cmake_args, "-DBUILD_FOR_R=ON")
 
   # Pass in R version, used to help find R executable for linking