regex.patch

commit 03940480b77c3d7ba8f5a851d74c6f4e2aefbad5
Author: Nikita Popov <npopov@redhat.com>
Date:   Tue Apr 19 15:43:59 2022 +0200

    Test std::regex

diff --git a/llvm/lib/FileCheck/FileCheck.cpp b/llvm/lib/FileCheck/FileCheck.cpp
index 6186af444e73..a56595254750 100644
--- a/llvm/lib/FileCheck/FileCheck.cpp
+++ b/llvm/lib/FileCheck/FileCheck.cpp
@@ -22,6 +22,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include <cstdint>
 #include <list>
+#include <regex>
 #include <set>
 #include <tuple>
 #include <utility>
@@ -1291,13 +1292,20 @@ Pattern::MatchResult Pattern::match(StringRef Buffer,
     RegExToMatch = TmpStr;
   }
 
-  SmallVector<StringRef, 4> MatchInfo;
-  unsigned int Flags = Regex::Newline;
+  std::regex_constants::syntax_option_type RegFlags =
+      std::regex_constants::ECMAScript;
+  //RegFlags |= std::regex_constants::multiline; // Requires C++17.
   if (IgnoreCase)
-    Flags |= Regex::IgnoreCase;
-  if (!Regex(RegExToMatch, Flags).match(Buffer, &MatchInfo))
+    RegFlags |= std::regex_constants::icase;
+  std::regex Reg(RegExToMatch.data(), RegExToMatch.size(), RegFlags);
+  std::cmatch CMatch;
+  if (!std::regex_search(Buffer.begin(), Buffer.end(), CMatch, Reg))
     return make_error<NotFoundError>();
 
+  SmallVector<StringRef, 4> MatchInfo;
+  for (const auto &M : CMatch)
+    MatchInfo.push_back(StringRef(M.first, (size_t)M.length()));
+
   // Successful regex match.
   assert(!MatchInfo.empty() && "Didn't get any match");
   StringRef FullMatch = MatchInfo[0];