On Fri, 22 Jan 2016 13:00:42 -0800, Anna Zaks said: >However, there is one corner case in C++ container overflow checking, >where this might not always hold. Specifically, if libc++ containers >cross from instrumented (rebuilt with ASan) to non-instrumented code, >Address Sanitizer might report container overflow false positives. >(Imagine two libraries, both using the same std::vector, only one of >them is instrumented. Push_back from the non-instrumented module will >not mark the memory for the newly added element as valid. Accessing the >element from the instrumented code, would trigger a false positive report.)
Oh that sounds like it! Our problem: - involves C++ - involves std::vector - started when we switched from libstdc++ to libc++ >What do these crashes look like? Are they C++ container overflow reports? Our Xcode-built app crashes at launch (with ASan) when some CMake-built (without ASan) C++ library code constructs a global variable. Before main(), starting from __cxx_global_var_init2(), we get a exc_bad_access at address=0x1. The typical backtrace is: #0 0x00000001044cf120 in std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:2074 #1 0x00000001044cf10b in std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:2075 #2 0x00000001044cf0ef in void std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::construct<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1673 #3 0x00000001044cf0be in void std::__1::allocator_traits<std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::__construct<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >(std::__1::integral_constant<bool, true>, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1600 #4 0x00000001044cf086 in void std::__1::allocator_traits<std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::construct<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >(std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:1453 #5 0x00000001044cf04e in std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::push_back(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&&) [inlined] at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:1609 #6 0x00000001044cef6d in gdcm::GlobalInternal::LoadDefaultPaths() at /Users/builder/official_builds/ITK/Modules/ThirdParty/GDCM/src/gdcm/Source/DataDictionary/gdcmGlobal.cxx:63 #7 0x00000001044cc53f in gdcm::Global::Global() at /Users/builder/official_builds/ITK/Modules/ThirdParty/GDCM/src/gdcm/Source/DataDictionary/gdcmGlobal.cxx:88 #8 0x00000001044cc3c5 in gdcm::Global::Global() at /Users/builder/official_builds/ITK/Modules/ThirdParty/GDCM/src/gdcm/Source/DataDictionary/gdcmGlobal.cxx:75 #9 0x0000000103dcd1a4 in ::__cxx_global_var_init2() at /Users/builder/official_builds/ITK/Modules/ThirdParty/GDCM/src/gdcm/Source/DataDictionary/gdcmGlobal.h:103 And indeed the bloody global is in a .h file, which I suppose means it'll show up in translation units built both with and without ASan. >Please, file a radar and provide us with more information about your >project, the libraries you link against, and the crashes you are seeing. >Attaching a project that would allow us to reproduce the issue would be >the most helpful. I think perhaps the mystery is solved. If I rebuild everything with ASan, then the problem will probably go away, right? Will try than on Monday. Cheers, -- ____________________________________________________________ Sean McBride, B. Eng s...@rogue-research.com Rogue Research www.rogue-research.com Mac Software Developer Montréal, Québec, Canada _______________________________________________ Do not post admin requests to the list. They will be ignored. Xcode-users mailing list (Xcode-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/xcode-users/archive%40mail-archive.com This email sent to arch...@mail-archive.com
