[LLVMbugs] [Bug 10069] New: Clang incorrectly reports substitution failure with default template arguments in function template

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10069

           Summary: Clang incorrectly reports substitution failure with
                    default template arguments in function template
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Keywords: compile-fail
          Severity: normal
          Priority: P
         Component: C++0x
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: jbytheway+llvm at gmail.com
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com


This is a case reduced from code in libstdc++ (as shipped with gcc 4.5.2).

The following code, which I believe is valid:

template<typename T, T a, T b=0, T c=1>
T f(T x)
{
  return x;
}

int main()
{
  f<unsigned int, 0>(0);
  return 0;
}

generates the following error when given to clang++ -std=gnu++0x:

template-int.cpp:9:3: error: no matching function for call to 'f'
  f<unsigned int, 0>(0);
  ^~~~~~~~~~~~~~~~~~
template-int.cpp:2:3: note: candidate template ignored: substitution failure
      [with T = unsigned int, a = 0, b = 0]
T f(T x)
  ^
1 error generated.

gcc 4.5.2 accepts this code.  Note that if you replace 'unsigned int' by just
'int' then it compiles fine.  Also, if the fourth template argument of f is
removed, then it compiles fine.

$ clang++ --version
clang version 3.0 (trunk 132479)
Target: x86_64-unknown-linux-gnu
Thread model: posix

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