[LLVM/Support] - Create no-arguments constructor for llvm::Regex

[grimar]

Summary

This is useful when need to defer the construction,
e.g. using Regex as a member of class.

[ruiu]

Ah, OK. LGTM. But you want to wait for someone who have contributed to this code.

[dblaikie]

Looks good - please commit.

llvm/trunk/lib/Support/Regex.cpp

 #include "llvm/Support/Regex.h"
 #include "regex_impl.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include <string>
 using namespace llvm;
 
+Regex::Regex() : error(REG_BADPAT), preg(nullptr) {}
+
 Regex::Regex(StringRef regex, unsigned Flags) {
   unsigned flags = 0;
   preg = new llvm_regex();
   preg->re_endp = regex.end();
   if (Flags & IgnoreCase) 
     flags |= REG_ICASE;
   if (Flags & Newline)
     flags |= REG_NEWLINE;

llvm/trunk/unittests/Support/RegexTest.cpp

 
 TEST_F(RegexTest, MoveAssign) {
   Regex r1("^[0-9]+$");
   Regex r2("abc");
   r2 = std::move(r1);
   EXPECT_TRUE(r2.match("916"));
 }
 
+TEST_F(RegexTest, NoArgConstructor) {
+  std::string Error;
+  Regex r1;
+  EXPECT_FALSE(r1.isValid(Error));
+  EXPECT_EQ("invalid regular expression", Error);
+  r1 = Regex("abc");
+  EXPECT_TRUE(r1.isValid(Error));
+}
+
 }