From 10f22d7054ae829f8cd9e21ca2e2c6241742f4a1 Mon Sep 17 00:00:00 2001 From: Eli Bendersky Date: Wed, 28 Nov 2012 19:00:02 +0000 Subject: Add backreference matching capabilities to Support/Regex, with appropriate unit tests. This change in itself is not expected to affect any functionality at this point, but it will serve as a stepping stone to improve FileCheck's variable matching capabilities. Luckily, our regex implementation already supports backreferences, although a bit of hacking is required to enable it. It supports both Basic Regular Expressions (BREs) and Extended Regular Expressions (EREs), without supporting backrefs for EREs, following POSIX strictly in this respect. And EREs is what we actually use (rightly). This is contrary to many implementations (including the default on Linux) of POSIX regexes, that do allow backrefs in EREs. Adding backref support to our EREs is a very simple change in the regcomp parsing code. I fail to think of significant cases where it would clash with existing things, and can bring more versatility to the regexes we write. There's always the danger of a backref in a specially crafted regex causing exponential matching times, but since we mainly use them for testing purposes I don't think it's a big problem. [it can also be placed behind a flag specific to FileCheck, if needed]. For more details, see: * http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-November/055840.html * http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20121126/156878.html llvm-svn: 168802 --- llvm/lib/Support/Regex.cpp | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'llvm/lib/Support/Regex.cpp') diff --git a/llvm/lib/Support/Regex.cpp b/llvm/lib/Support/Regex.cpp index d293da07d68..0a5479a548f 100644 --- a/llvm/lib/Support/Regex.cpp +++ b/llvm/lib/Support/Regex.cpp @@ -27,7 +27,9 @@ Regex::Regex(StringRef regex, unsigned Flags) { flags |= REG_ICASE; if (Flags & Newline) flags |= REG_NEWLINE; - error = llvm_regcomp(preg, regex.data(), flags|REG_EXTENDED|REG_PEND); + if (!(Flags & BasicRegex)) + flags |= REG_EXTENDED; + error = llvm_regcomp(preg, regex.data(), flags|REG_PEND); } Regex::~Regex() { -- cgit v1.2.3