Remove `-Wdeclaration-after-statement` from gcc options; #5159

build_config/travis.rb

@@ -4,7 +4,6 @@ MRuby::Build.new('full-debug') do |conf|
 
   # include all core GEMs
   conf.gembox 'full-core'
-  conf.cc.flags += %w(-Werror=declaration-after-statement)
   conf.cc.defines += %w(MRB_GC_STRESS MRB_ENABLE_DEBUG_HOOK)
 
   conf.enable_test
@@ -15,7 +14,6 @@ MRuby::Build.new do |conf|
 
   # include all core GEMs
   conf.gembox 'full-core'
-  conf.cc.flags += %w(-Werror=declaration-after-statement)
   conf.compilers.each do |c|
     c.defines += %w(MRB_GC_FIXED_ARENA)
   end

tasks/toolchains/gcc.rake

@@ -2,7 +2,7 @@ MRuby::Toolchain.new(:gcc) do |conf, params|
   default_command = params[:default_command] || 'gcc'
   compiler_flags = %w(-g -O3 -Wall -Wundef)
   c_mandatory_flags = %w(-std=gnu99)
-  cxx_invalid_flags = %w(-Wdeclaration-after-statement -Werror-implicit-function-declaration)
+  cxx_invalid_flags = %w(-Werror-implicit-function-declaration)
 
   [conf.cc, conf.objc, conf.asm, conf.cxx].each do |compiler|
     if compiler == conf.cxx