Crash when returning inside while-loop

[veddan]

When I try to run the following program it crashes with an error message from glibc.

fn main() {
  let s = "hej";
  while s != "" {
    ret;
  }
}

The error message is

*** glibc detected *** ./crash: double free or corruption (fasttop): 0x0000000001a2c7d0 ***

I tried running the program with valgrind. It then produced a different error message:

rust: fatal, 'live_allocs < 1' failed, ./src/rt/memory_region.cpp:54 

If I change the loop to "while true", the program finishes without error.

[brson]

It looks like this is due to the basic block containing the loop condition being a parent of the loop body, so when we run all the cleanups for ret or break it runs the condition's cleanups (a 2nd time).

[brson]

Fixed by aeb445b