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Fix handling of the From parameter in StringRef::find.

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Enable bounds checking to catch this kind of bug earlier.

llvm-svn: 142247
This commit is contained in:
Benjamin Kramer 2011-10-17 20:49:40 +00:00
parent 5d4f239d0a
commit 524eb5859f
1 changed files with 5 additions and 2 deletions
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7
lib/Support/StringRef.cpp
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@ -153,19 +153,22 @@ size_t StringRef::find(StringRef Str, size_t From) const {
return npos;
}
if (From >= Length)
return npos;
// Build the bad char heuristic table, with uint8_t to reduce cache thrashing.
uint8_t BadCharSkip[256];
std::memset(BadCharSkip, N, 256);
for (unsigned i = 0; i != N-1; ++i)
BadCharSkip[(uint8_t)Str[i]] = N-1-i;
unsigned Len = Length, Pos = min(From, Length);
unsigned Len = Length-From, Pos = From;
while (Len >= N) {
if (substr(Pos, N).equals(Str)) // See if this is the correct substring.
return Pos;
// Otherwise skip the appropriate number of bytes.
uint8_t Skip = BadCharSkip[(uint8_t)Data[Pos+N-1]];
uint8_t Skip = BadCharSkip[(uint8_t)(*this)[Pos+N-1]];
Len -= Skip;
Pos += Skip;
}