[llvm-bugs] [Bug 34365] New: Static analyzer is very conservative with atomic ops

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34365

            Bug ID: 34365
           Summary: Static analyzer is very conservative with atomic ops
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
          Assignee: kremenek at apple.com
          Reporter: george.burgess.iv at gmail.com
                CC: llvm-bugs at lists.llvm.org

$ cat tc.cpp
void bar() {
  int i = 2;
  char *c = new char;
  if (__sync_fetch_and_sub(&i, 1) == 1) delete c;
  if (__sync_fetch_and_sub(&i, 1) == 1) delete c;
}

$ clang++ --analyze tc.cpp -std=c++11
tc.cpp:5:41: warning: Attempt to free released memory
  if (__sync_fetch_and_sub(&i, 1) == 1) delete c;
                                        ^~~~~~~~
tc.cpp:6:1: warning: Potential leak of memory pointed to by 'c'
}
^

I'm unsure if it's possible to do much better than this in general, since
atomic ops are inherently annoying to reason about. That said, this issue makes
the analyzer pretty noisy when it's analyzing home-grown shared_ptr
implementations.

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