[LLVMbugs] [Bug 9968] New: False positive "unused variable '__range'" with ranged for loop in template

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri May 20 08:32:50 PDT 2011


           Summary: False positive "unused variable '__range'" with ranged
                    for loop in template
           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: llvmbugs at cs.uiuc.edu, dgregor at apple.com

The following program results in a warning when compiled with -Wunused:

template <typename T>
struct Vector {
    void doIt()
        for (auto& e : elements)
            (void) e;

    T    elements[10];

int main(int, char**)
    Vector<int>    vector;

This results in:

$ clang -std=c++0x -fsyntax-only -Wunused clang.cpp
clang.cpp:7:18: warning: unused variable '__range' [-Wunused-variable]
                for (auto& e : elements)
clang.cpp:18:9: note: in instantiation of member function 'Vector<int>::doIt'
requested here
1 warning generated.

clang generates correct code for the loop. It is just the warning that is

It also only happens if the loop's "__range" variable is dependent on the
template parameter(s).

My clang version:

$ clang --version
clang version 3.0 (trunk 131126)

Target: x86_64-apple-darwin10.7.0
Thread model: posix

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