[LLVMbugs] [Bug 16704] New: False positive for Logic Error on std::set_difference when using std::insert(std::set<>, std::set<>::iterator)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16704

            Bug ID: 16704
           Summary: False positive for Logic Error on std::set_difference
                    when using std::insert(std::set<>,
                    std::set<>::iterator)
           Product: clang
           Version: unspecified
          Hardware: Macintosh
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
          Assignee: kremenek at apple.com
          Reporter: clang-bugzilla at cabbits.net
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Seen on XCode 4.6,
Apple clang version 4.0 (tags/Apple/clang-421.10.60) (based on LLVM 3.1svn)

The following code compiled in obj-c++ in a new XCode project OSX C++ Library
template (but seen using other templates as well):

  std::set<int> set1 = {1, 2, 5, 7, 9};
  std::set<int> set2 = {2, 3, 5, 8, 10};
  std::set<int> set3;

  std::set_difference(set1.begin(), set1.end(),
                      set2.begin(), set2.end(),
                      std::inserter(set3, set3.begin()));

Produces a logic error:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:253:30:
Access to field '__is_black_' results in a dereference of a null pointer
(loaded from field '__parent_')

Trace:

/Users/nall/Desktop/TestLibrary/DemoClass.mm:21:3: Calling 'set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5209:1:
Entered call from 'TestSet'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5214:12:
Calling 'set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5193:1:
Entered call from 'set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5204:12:
Calling '__set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5168:1:
Entered call from 'set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5172:5:
Looping back to the head of the loop
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5172:5:
Looping back to the head of the loop
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5172:5:
Looping back to the head of the loop
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/algorithm:5178:13:
Calling 'operator='
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/iterator:701:5:
Entered call from '__set_difference'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/iterator:702:17:
Calling 'insert'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/set:533:5:
Entered call from 'operator='
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/set:535:17:
Calling '__insert_unique'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:1865:1:
Entered call from 'insert'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:1874:9:
Calling '__insert_node_at'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:1690:1:
Entered call from '__insert_unique'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:1701:5:
Calling '__tree_balance_after_insert'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:249:1:
Entered call from '__insert_node_at'
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/c++/v1/__tree:253:30:
Access to field '__is_black_' results in a dereference of a null pointer
(loaded from field '__parent_')

This does not occur when a std::vector<> or other containers are used with
std::inserter().  This appears to be a spurious warning, but I am not sure of
the proper resolution.

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