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Fix UBSAN issue of passing nullptr to memcmp

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Summary:
As explained in the comments, Sometimes we create Slice(nullptr, 0) in our code base which cause us to do calls like
```
memcmp(nullptr, "abc", 0);
```
That's fine since the len is equal 0, but UBSAN is not happy about it
so disable UBSAN for this function and add an assert instead
Closes https://github.com/facebook/rocksdb/pull/2616

Differential Revision: D5458326

Pulled By: IslamAbdelRahman

fbshipit-source-id: cfca32abe30f7d8f760c9f77ecd9543dfb1170dd
This commit is contained in:
Islam AbdelRahman 2017-07-24 10:47:19 -07:00 committed by Facebook Github Bot
parent 16e0388205
commit a4c42e8007
1 changed files with 10 additions and 0 deletions
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10
include/rocksdb/slice.h
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@ -213,8 +213,18 @@ inline bool operator!=(const Slice& x, const Slice& y) {
return !(x == y);
}
// UBSAN complain that we pass nullptr to memcmp that's fine since
// we always do that for a string of len = 0
#ifdef ROCKSDB_UBSAN_RUN
#if defined(__clang__)
__attribute__((__no_sanitize__("undefined")))
#elif defined(__GNUC__)
__attribute__((__no_sanitize_undefined__))
#endif
#endif
inline int Slice::compare(const Slice& b) const {
const size_t min_len = (size_ < b.size_) ? size_ : b.size_;
assert((data_ != nullptr && b.data_ != nullptr) || min_len == 0);
int r = memcmp(data_, b.data_, min_len);
if (r == 0) {
if (size_ < b.size_) r = -1;