[LLVMbugs] [Bug 14785] New: clang++ ignores friend function definition within class scope (allowing redefinition)

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Jan 2 09:53:52 PST 2013


             Bug #: 14785
           Summary: clang++ ignores friend function definition within
                    class scope (allowing redefinition)
           Product: clang
           Version: 3.2
          Platform: PC
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid, miscompilation
          Severity: normal
          Priority: P
         Component: C++11
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: irrequietus at gmail.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 9798
  --> http://llvm.org/bugs/attachment.cgi?id=9798
original testcase file used (ill formed code that compiles, but should not)


The following code snippet is ill - formed and clang++ should not compile it
warning of redefinition, however it is accepted as legal. There can be several
variations of this snippet and I am simply posting one of them.

In brief, in - class scope friend function *definition* is ignored when lookup
is performed. Affected are both C++03 and C++11 implementations of the standard
in clang++ at least in the following versions I could test:

clang version 3.1 (release), 3.2 (release), and r170492

#include <cstdio>

template<typename T>
struct Somewhat {
    void internal() const
    { printf("internal called\n"); }

    friend void operator+(int const &, Somewhat<T> const &)
    {} // notice the in - class scope definition

void operator+(int const &, Somewhat<char> const &x)
{ x.internal(); }

int main() {
    // internal() called, the friend in - class *definition* ignored.
    1 + Somewhat<char>();
    return 0;


gcc (4.6.3, 4.7.1, 4.7.2 and 4.8.x snapshot tested) and icc (13.0.0 20120731 as
I am informed) give an error informing the user of a redefinition error for the
operator+ function as per language standard, while clang++ ignores completely
the in - class scope definition of the friend function.

Any help?

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