False(?) positive from new Address Sanitizer C++ STL container check
False(?) positive from new Address Sanitizer C++ STL container check
- Subject: False(?) positive from new Address Sanitizer C++ STL container check
- From: Jens Alfke <email@hidden>
- Date: Thu, 25 May 2017 10:24:56 -0700
| Has anyone tried using the newish “Enable C++ Container Overflow Checks For Static Analyzer” build setting? I’m not sure what version of Xcode it appeared in, but I just noticed it yesterday and am trying it out. I immediately ran into what looks like a false positive, where the sanitizer complains about a buffer overflow being committed by an “__RAII_IncreaseAnnotator” class that seems to be part of the implementation of this overflow checker:
================================================================= ==53680==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fff5fb032d8 at pc 0x000101a7d8c8 bp 0x7fff5fb031c0 sp 0x7fff5fb031b8 WRITE of size 8 at 0x7fff5fb032d8 thread T0 #0 0x101a7d8c7 in std::__1::vector<fleece::alloc_slice, std::__1::allocator<fleece::alloc_slice> >::__RAII_IncreaseAnnotator::__RAII_IncreaseAnnotator(std::__1::vector<fleece::alloc_slice, std::__1::allocator<fleece::alloc_slice> > const&, unsigned long) vector:867 #1 0x101a7d794 in std::__1::vector<fleece::alloc_slice, std::__1::allocator<fleece::alloc_slice> >::__RAII_IncreaseAnnotator::__RAII_IncreaseAnnotator(std::__1::vector<fleece::alloc_slice, std::__1::allocator<fleece::alloc_slice> > const&, unsigned long) vector:867 #2 0x101f4fe6a in fleece::SharedKeys::add(fleece::slice) vector:1642
. . .
The offending address seems to be within a variable ‘__annotator.i’ inserted by the compiler:
Address 0x7fff5fb032d8 is located in stack of thread T0 at offset 88 in frame
This frame has 7 object(s): [32, 48) 'agg.tmp.i.i.i.i' [64, 65) 'ref.tmp.i.i' [80, 81) '__annotator.i' [96, 112) 'str' <== Memory access at offset 88 underflows this variable [128, 144) 'agg.tmp' [160, 168) 'info' [192, 208) 'agg.tmp8'
My own code is just calling vector::emplace_back.
(Yes, I’ll file a bug report.)
—Jens |
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