[Bug c++/12668] Strange warnings with -O1 -Wunreachable-code in 3.3.1,3.3.2,3.4

["rmerkert at alphatech dot com" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12668



------- Additional Comments From rmerkert at alphatech dot com  2003-10-18 13:51 -------
One more example, where I don't really want to see warning:
cat > test.cpp <<EOF
#include <iostream>
struct Foo {

  inline Foo (int x) : foo(0) {init(x); }

  private:
   inline void init (int x) {
     if (x!=0)
       foo = x + 1;
   }
  int foo;
};


struct Z {
  Z (int x) : foo(0),z(x) {}
  Foo foo;
  int z;
};
int main (int argc, int argv)
{
  Z z(argc);
  ::std::cerr << "Z: " << z.z << ::std::endl;
  return 0;
}


EOF
g++ -O1 -Wunreachable-code test.cpp


The warning in this case is:
test.cpp: In function `int main(int, int)':
test.cpp:9: warning: will never be executed

There is no unreachable code in the example - it's just that 
by choosing a certain parameter, a path in the program does not
need to be executed. That's not the same as being unreachable, that's
optimizing away things.
I've been getting lots of these warnings when I compile with O1 because of this
kind of situation. I think things are just propagated too far down the line.
What if I had 7 nested inlined functions that turn out to be "unreachable".