[LLVMbugs] [Bug 11939] New: Regression: Crash on codegen for reference to temporary(?)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11939

             Bug #: 11939
           Summary: Regression: Crash on codegen for reference to
                    temporary(?)
           Product: clang
           Version: trunk
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++0x
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: jonathan.sauer at gmx.de
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8013
  --> http://llvm.org/bugs/attachment.cgi?id=8013
Complete log of clang run

The following program crashes clang r149863 during codegen:

static void foo(const unsigned int&)
{
}

// Adapted from libc++'s chrono header
template <typename Rep, typename Period>
class duration {
    public:
        duration(const Rep&);

        Rep count() const;
};

typedef duration<long long, short>  milliseconds;
typedef duration<long long, int>    nanoseconds;

template <class ToDuration, class Rep, class Period>
ToDuration duration_cast(const duration<Rep, Period>& d);

int main(int, char**)
{
    long long const millisPassed =
duration_cast<milliseconds>(nanoseconds(1)).count();  // Crashes
    //unsigned int const millisPassed =
duration_cast<milliseconds>(nanoseconds(1)).count();  // OK
    //long long const millisPassed = 462379463473946239LL; // OK

    foo(millisPassed);
}


This results in (full log attached):

$ clang++ -std=c++0x -v clang.cpp

Assertion failed: ((ND->isUsed(false) || !isa<VarDecl>(ND) ||
!E->getLocation().isValid()) && "Should not use decl without marking it
used!"), function EmitDeclRefLValue, file
/Users/rynnsauer/LLVM/llvm/tools/clang/lib/CodeGen/CGExpr.cpp, line 1377.
[...]
1.    <eof> parser at end of file
2.    clang.cpp:22:5: LLVM IR generation of declaration 'main'
3.    clang.cpp:22:5: Generating code for declaration 'main'
4.    clang.cpp:23:1: LLVM IR generation of compound statement ('{}')

It seems that this happens while creating a const reference to the temporary
unsigned int into which <millisPassed> is converted. Changing <millisPassed>'s
type to unsigned int resolves the crash (perhaps because a temporary is no
longer necessary). So does directly assigning a value to <millisPassed>.

Clang r149240 does not crash when compiling the program.

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