[Bug fortran/91537] New: Memory leak involving nested allocatable derived types

[townsend at astro dot wisc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91537

            Bug ID: 91537
           Summary: Memory leak involving nested allocatable derived types
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: townsend at astro dot wisc.edu
  Target Milestone: ---

Created attachment 46748
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46748&action=edit
Leak demonstration program

The attached test program demonstrates a memory leak on gfortran 8.3.0.
Intriguingly, valgrind reports no leak; but the memory usage grows steadily
over time, even though only ALLOCATABLE arrays are used. By the end of
execution, 4GB  is being used.

To demonstrate the memory growth, I use the routine system_mem_usage, which
looks at files inside /proc to find the current RSS. Of course, this only works
on Linux -- for those on other platforms, you may have to comment out (or
rework) the call.

Typical output is as follows (from ./test_leak_new | tail -10):

          91     3682816
          92     3722680
          93     3762808
          94     3802672
          95     3842800
          96     3882664
          97     3922792
          98     3962656
          99     4002784
         100     4042648

The first number is the iteration number, the second is the RSS. So, 4GB by the
end of execution, despite the fact that bp is explicitly deallocated at the end
of each loop.

The test program may seem a little contrived, but it's a cut-down version of
production code (which shows the same valgrind-invisible leak behavior).

cheers,

Rich