Implement clang tool that converts std::string("") to std::string().

tools/clang/empty_string/Makefile

Index: tools/clang/empty_string/Makefile
diff --git a/tools/clang/empty_string/Makefile b/tools/clang/empty_string/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..1f9a232cdf9876864816084c2892fa38df8e468f
--- /dev/null
+++ b/tools/clang/empty_string/Makefile
@@ -0,0 +1,25 @@
+##===-------- tools/toolTemplate/Makefile ------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure

[Nico, 2013/03/27 16:35:29]

Same license question

[dcheng, 2013/03/28 00:10:17]

I've reimplemented the Makefile (I know, it looks basically the same) so now we
can use the Chrome header.

+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+CLANG_LEVEL := ../..
+
+TOOLNAME = empty-string
+NO_INSTALL = 1
+
+# No plugins, optimize startup time.

[Nico, 2013/03/27 16:35:29]

Does this have a measurable impact?

[dcheng, 2013/03/28 00:10:17]

On a relatively small sample (~47 second runs)... nope. =/
But all the tools checked into Clang seem to have this stanza in their Makefile.
This is supposedly a big optimization (4x difference in dyld startup time) for
darwin.

[Nico, 2013/03/29 22:30:36]

We don't build regular clang with it (else the plugin wouldn't work). If you
can't measure the impact of this, I'd drop this.

[dcheng, 2013/03/29 22:42:55]

I'll take it out for now and measure on OS X later.

+TOOL_NO_EXPORTS = 1
+
+include $(CLANG_LEVEL)/../../Makefile.config
+LINK_COMPONENTS := $(TARGETS_TO_BUILD) asmparser bitreader support mc
+USEDLIBS = clangTooling.a clangFrontend.a clangSerialization.a clangDriver.a \
+					 clangRewriteFrontend.a clangRewriteCore.a \
+					 clangParse.a clangSema.a clangAnalysis.a \
+					 clangAST.a clangASTMatchers.a clangEdit.a clangLex.a clangBasic.a
+
+include $(CLANG_LEVEL)/Makefile