[LLVMbugs] [Bug 13385] New: C++ parameter defaults are ignored

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13385

             Bug #: 13385
           Summary: C++ parameter defaults are ignored
           Product: clang
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
        AssignedTo: kremenek at apple.com
        ReportedBy: craig+clang at trickplay.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8916
  --> http://llvm.org/bugs/attachment.cgi?id=8916
Sample C++ program showing default arguments being ignored when passed
implicitly

I have a C++ function which uses parameter defaults, eg:

MyObject * get_obj(bool destroy = false);

If I call that function explicitly with

foo = get_obj(false);

the static analyzer treats it differently than if I call it with the (same)
implicit argument:

foo = get_object();

The attached short example program shows this problem -- essentially, in my
code if "false" is passed to that function, it will return non-null or
assert().  If I explicitly pass "false", then clang correctly realizes that foo
will be non-NULL.  But with the implicit argument, clang thinks foo can be NULL
and complains.

Compile sample with this:

scan-build clang++ -o test test.cpp 
test.cpp:38:24: warning: Access to field 'some_contents' results in a
dereference of a null pointer (loaded from variable 'ptr')
    ptr->some_contents = 42;
    ~~~                ^
1 warning generated.
scan-build: 1 bugs found.

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