[Bug c++/80138] New: spurious warning: assuming signed overflow does not occur when ...

[julienpommier at free dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80138

            Bug ID: 80138
           Summary: spurious warning: assuming signed overflow does not
                    occur when ...
           Product: gcc
           Version: 6.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: julienpommier at free dot fr
  Target Milestone: ---

The following code triggers a spurious warning with gcc 6.3. It disappears if I
write '(w >= y) && (w < y+h)' instead of 'w >=y && < w < y+h'

/* build with: g++ -Wall -O2 foo.cc */
#include <iostream>

struct Rng {
  int y, h;
  bool contains (int w)
  {
    return w >= y && w < y + h;
  }
};

const Rng& getRng ();

int main(int argc, char**) {
  int y = argc;
  Rng r = getRng();
  if (!r.contains(y)) {
    int yc = r.y+10;
    if (r.contains(yc)) {
      return 1;
    }
  }
  return 0;
}