[LLVMbugs] [Bug 10506] New: instantiation of '0x for-range statements sloshes together temporaries

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10506

           Summary: instantiation of '0x for-range statements sloshes
                    together temporaries
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++0x
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: rjmccall at apple.com
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com


By inspection: TreeTransform on CXXForRangeStmt is not building
CXXExprWithCleanups nodes appropriately for the condition and increment
expressions.  Both of these typically would not require temporaries, but they
certainly could if, e.g., the arguments to the equality operator have class
type or the increment expression returns an (ignored) value of class type.

Something like this:

struct needs_temporary {
  needs_temporary();
  needs_temporary(const needs_temporary &);
  ~needs_temporary();
};

struct iterator {
  needs_temporary temp;

  friend bool operator!=(iterator x, iterator y); // or even returning a
temporary with a conversion to bool
  needs_temporary operator++();  
};

struct has_iterator {};
iterator begin(has_iterator);
iterator end(has_iterator);

template <class T> void test() {
  for (auto var : T()) {}
}
template void test<has_iterator>();

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