[LLVMbugs] [Bug 14820] New: warn on invalid assignment

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14820

             Bug #: 14820
           Summary: warn on invalid assignment
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: nicholas at mxc.ca
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


I think this C code has undefined behaviour:

  enum E { X, Y, Z };
  void test() {
    enum E e = -1;
  }

and we don't currently warn on that. If you later query e == -1 we warn on
*that*, but that's somewhat redundant as UB has already occurred.

We have a similar problem in C++, but at least it's safer:

  enum E { X, Y, Z };
  void test() {
    E e = (E)-1;
  }

doesn't warn. We should also warn on 'return (E)-1;' and similar.

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