From f5ba5ffe80c52e448bf162686c21c82f166ab6c0 Mon Sep 17 00:00:00 2001 From: Philipp Bartsch Date: Thu, 13 Jun 2019 14:42:10 +0000 Subject: fix zero terminated string issue In C "strings" are zero terminated. Functions like strcmp/strncmp/memcmp/... work on them. We have to be careful to not ignore the last byte. --- llvm_mode/compare-transform-pass.so.cc | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'llvm_mode/compare-transform-pass.so.cc') diff --git a/llvm_mode/compare-transform-pass.so.cc b/llvm_mode/compare-transform-pass.so.cc index c89655ea..d9a1f945 100644 --- a/llvm_mode/compare-transform-pass.so.cc +++ b/llvm_mode/compare-transform-pass.so.cc @@ -184,6 +184,7 @@ bool CompareTransform::transformCmps(Module &M, const bool processStrcmp, const Value *Str1P = callInst->getArgOperand(0), *Str2P = callInst->getArgOperand(1); StringRef Str1, Str2, ConstStr; + std::string TmpConstStr; Value *VarStr; bool HasStr1 = getConstantStringInfo(Str1P, Str1); getConstantStringInfo(Str2P, Str2); @@ -202,21 +203,20 @@ bool CompareTransform::transformCmps(Module &M, const bool processStrcmp, const } if (HasStr1) { - ConstStr = Str1; + TmpConstStr = Str1.str(); VarStr = Str2P; constLen = isMemcmp ? sizedLen : GetStringLength(Str1P); } else { - ConstStr = Str2; + TmpConstStr = Str2.str(); VarStr = Str1P; constLen = isMemcmp ? sizedLen : GetStringLength(Str2P); } - /* bugfix thanks to pbst */ - /* ignore terminating '\0' in string for strcmp */ - if (!isSizedcmp && constLen > 0) { - constLen--; - } + /* properly handle zero terminated C strings by adding the terminating 0 to + * the StringRef (in comparison to std::string a StringRef has built-in + * runtime bounds checking, which makes debugging easier) */ + TmpConstStr.append("\0", 1); ConstStr = StringRef(TmpConstStr); if (isSizedcmp && constLen > sizedLen) { constLen = sizedLen; -- cgit 1.4.1