mkmf.rb: avoid interference

* lib/mkmf.rb (try_cppflags, try_cflags, try_ldflags): get rid of
  interference by modifying global variables in have_devel? method.
  [ruby-core:67962] [Bug ruby#10821]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Conflicts:
	ChangeLog

lib/mkmf.rb

@@ -610,9 +610,7 @@ def with_cppflags(flags)
   end
 
   def try_cppflags(flags)
-    with_cppflags(flags) do
-      try_header("int main() {return 0;}")
-    end
+    try_header(MAIN_DOES_NOTHING, flags)
   end
 
   def with_cflags(flags)
@@ -624,9 +622,7 @@ def with_cflags(flags)
   end
 
   def try_cflags(flags)
-    with_cflags(flags) do
-      try_compile("int main() {return 0;}")
-    end
+    try_compile(MAIN_DOES_NOTHING, flags)
   end
 
   def with_ldflags(flags)
@@ -638,9 +634,7 @@ def with_ldflags(flags)
   end
 
   def try_ldflags(flags)
-    with_ldflags(flags) do
-      try_link("int main() {return 0;}")
-    end
+    try_link(MAIN_DOES_NOTHING, flags)
   end
 
   def try_static_assert(expr, headers = nil, opt = "", &b)

test/mkmf/base.rb

@@ -49,7 +49,9 @@ def write(s)
       @buffer << s if @out
     end
   end
+end
 
+module TestMkmf::Base
   attr_reader :stdout
 
   def mkmflog(msg)
@@ -84,7 +86,7 @@ def setup
     @tmpdir = Dir.mktmpdir
     @curdir = Dir.pwd
     @mkmfobj = Object.new
-    @stdout = Capture.new
+    @stdout = TestMkmf::Capture.new
     Dir.chdir(@tmpdir)
     @quiet, Logging.quiet = Logging.quiet, true
     init_mkmf
@@ -127,3 +129,11 @@ def config_value(name)
     nil
   end
 end
+
+class TestMkmf
+  include TestMkmf::Base
+
+  def assert_separately(args, src, *rest)
+    super(args + ["-r#{__FILE__}"], "extend TestMkmf::Base; setup\n#{src}", *rest)
+  end
+end

test/mkmf/test_flags.rb

@@ -31,5 +31,26 @@ def test_valid_warnflags
       $warnflags = warnflags
       $extmk = val
     end
+
+    def test_try_ldflag_invalid_opt
+      assert_separately([], <<-'end;') #do
+        assert(!try_ldflags("----------"))
+        assert(have_devel?, TestMkmf::MKMFLOG)
+      end;
+    end
+
+    def test_try_cflag_invalid_opt
+      assert_separately([], <<-'end;') #do
+        assert(!try_cflags("----------"))
+        assert(have_devel?, TestMkmf::MKMFLOG)
+      end;
+    end
+
+    def test_try_cppflag_invalid_opt
+      assert_separately([], <<-'end;') #do
+        assert(!try_cppflags("----------"))
+        assert(have_devel?, TestMkmf::MKMFLOG)
+      end;
+    end
   end
 end