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fix zero terminated string issue

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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.
This commit is contained in:
Philipp Bartsch 2019-06-13 14:42:10 +00:00
parent 0113c4f834
commit f5ba5ffe80
1 changed files with 7 additions and 7 deletions
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14
llvm_mode/compare-transform-pass.so.cc
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@ -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;