Compile C files by C compiler when C++ files mixed.

ref #3267 #3470

By this commit, mruby do not use C++ ABI mode unless
you specify explicitly. It compiles C files by C
compilers, with C++ exception enabled when it sees
C++ files in your configured mrbgems.

I haven't tried visualcpp, so please submit an issue
if you see any problem with C++ gems on Windows.

5 files changed, 18 insertions, 4 deletions

diff --git a/tasks/mruby_build.rake b/tasks/mruby_build.rake
index bd911493d..46459cf6c 100644
--- a/tasks/mruby_build.rake
+++ b/tasks/mruby_build.rake
@@ -113,13 +113,23 @@ module MRuby
       @cxx_exception_disabled = true
     end
 
+    def enable_cxx_exception
+      @cxx_exception_disabled = false
+      compilers.each { |c|
+        c.defines += %w(MRB_ENABLE_CXX_EXCEPTION)
+        c.flags << c.cxx_exception_flag
+      }
+    end
+
     def cxx_abi_enabled?
       @cxx_abi_enabled
     end
 
     def enable_cxx_abi
-      return if @cxx_exception_disabled or @cxx_abi_enabled
-      compilers.each { |c| c.defines += %w(MRB_ENABLE_CXX_EXCEPTION) }
+      return if @cxx_abi_enabled
+      unless @cxx_exception_disabled
+        enable_cxx_exception
+      end
       compilers.each { |c| c.flags << c.cxx_compile_flag }
       linker.command = cxx.command if toolchains.find { |v| v == 'gcc' }
       @cxx_abi_enabled = true
diff --git a/tasks/mruby_build_commands.rake b/tasks/mruby_build_commands.rake
index d688077ff..694b4a24c 100644
--- a/tasks/mruby_build_commands.rake
+++ b/tasks/mruby_build_commands.rake
@@ -41,7 +41,7 @@ module MRuby
   class Command::Compiler < Command
     attr_accessor :flags, :include_paths, :defines, :source_exts
     attr_accessor :compile_options, :option_define, :option_include_path, :out_ext
-    attr_accessor :cxx_compile_flag
+    attr_accessor :cxx_compile_flag, :cxx_exception_flag
 
     def initialize(build, source_exts=[])
       super(build)
diff --git a/tasks/mruby_build_gem.rake b/tasks/mruby_build_gem.rake
index 9a802097f..b48df6510 100644
--- a/tasks/mruby_build_gem.rake
+++ b/tasks/mruby_build_gem.rake
@@ -38,7 +38,7 @@ module MRuby
       cxx_srcs = ['src', 'test', 'tools'].map do |subdir|
         Dir.glob("#{Gem.current.dir}/#{subdir}/*.{cpp,cxx,cc}")
       end.flatten
-      enable_cxx_abi unless cxx_srcs.empty?
+      enable_cxx_exception unless cxx_srcs.empty?
 
       Gem.current
     end
diff --git a/tasks/toolchains/gcc.rake b/tasks/toolchains/gcc.rake
index 59ae015ac..f370c0abf 100644
--- a/tasks/toolchains/gcc.rake
+++ b/tasks/toolchains/gcc.rake
@@ -7,6 +7,7 @@ MRuby::Toolchain.new(:gcc) do |conf, _params|
     cc.option_define = '-D%s'
     cc.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'
     cc.cxx_compile_flag = '-x c++ -std=c++03'
+    cc.cxx_exception_flag = '-fexceptions'
   end
 
   [conf.cxx].each do |cxx|
@@ -17,6 +18,7 @@ MRuby::Toolchain.new(:gcc) do |conf, _params|
     cxx.option_define = '-D%s'
     cxx.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'
     cxx.cxx_compile_flag = '-x c++ -std=c++03'
+    cxx.cxx_exception_flag = '-fexceptions'
   end
 
   conf.linker do |linker|
diff --git a/tasks/toolchains/visualcpp.rake b/tasks/toolchains/visualcpp.rake
index 5f5bab9c2..5bc24a73a 100644
--- a/tasks/toolchains/visualcpp.rake
+++ b/tasks/toolchains/visualcpp.rake
@@ -8,6 +8,7 @@ MRuby::Toolchain.new(:visualcpp) do |conf, _params|
     cc.option_define = '/D%s'
     cc.compile_options = "%{flags} /Fo%{outfile} %{infile}"
     cc.cxx_compile_flag = '/TP'
+    cc.cxx_exception_flag = '/EHs'
   end
 
   conf.cxx do |cxx|
@@ -18,6 +19,7 @@ MRuby::Toolchain.new(:visualcpp) do |conf, _params|
     cxx.option_define = '/D%s'
     cxx.compile_options = "%{flags} /Fo%{outfile} %{infile}"
     cxx.cxx_compile_flag = '/TP'
+    cxx.cxx_exception_flag = '/EHs'
   end
 
   conf.linker do |linker|