Created attachment 31836 [details]
The program in full to replicate this bug

This is pretty trivial but the warning outputs incorrect information. given the line:

int foo = static_cast< int >( 1, 2, 3 );

G++ reports that value 2 and 3 are not used, when in fact 1 and 2 are not used.

G++ 4.8.1's output (with -Wall):
test.cpp: In function ‘int main()’:
test.cpp:15:35: warning: left operand of comma operator has no effect [-Wunused-value]
  int foo = static_cast< int >( 1, 2, 3 );
                                   ^
test.cpp:15:38: warning: right operand of comma operator has no effect [-Wunused-value]
  int foo = static_cast< int >( 1, 2, 3 );
                                      ^


Clang 3.2.7 gets it right, however:

test.cpp:15:32: warning: expression result unused [-Wunused-value]
        int foo = static_cast< int >( 1, 2, 3 );
                                      ^
test.cpp:15:35: warning: expression result unused [-Wunused-value]
        int foo = static_cast< int >( 1, 2, 3 );
                                         ^
2 warnings generated.