[Bug fortran/120637] Memory leak in finalization gfortran 15.1.1

[antony at cosmologist dot info]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120637

--- Comment #1 from Antony Lewis <antony at cosmologist dot info> ---
Here's a code that reproduces a similar issue without explicit final.


    module MiscUtils
    implicit none

    contains

    logical function isFloat0(R)
    class(*), intent(in) :: R

    select type(R)
    type is (real)
        isFloat0 = .true.
    end select
    end function isFloat0

    end module MiscUtils

    module results3
    implicit none
    public

    Type ClTransferData2
      real, dimension(:,:,:), allocatable :: Delta_p_l_k
    end type ClTransferData2

    type TCLdata2
       Type(ClTransferData2) :: CTransScal, CTransTens, CTransVec
    end type TCLdata2 

    type :: CAMBdata2
        Type(TClData2) :: CLdata2
    end type  

    end module results3

program driver
   use results3
   integer i
   do i=1, 2
   call test()   
   end do

   contains

   subroutine test
       implicit none
       class(CAMBdata2), pointer :: Data

       allocate(CAMBdata2::Data)

       allocate(Data%ClData2%CTransScal%Delta_p_l_k(3, 1000, 1000)) 
       allocate(Data%ClData2%CTransVec%Delta_p_l_k(3, 1000, 1000))
       deallocate(Data)

   end subroutine test

 end program driver


docker run --rm -v "$(pwd):/workspace" -w /workspace
cmbant/docker-gcc-build:devel bash -c "
     echo 'Building CAMB...' && gfortran -v &&
     gfortran camb_memory_leak_test_nofinal.f90 && valgrind ./a.out"
Building CAMB...
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-linux-gnu/16.0.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../configure --enable-languages=c,c++,fortran
--disable-multilib --disable-bootstrap --build=x86_64-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 16.0.0 20250611 (experimental) (GCC)
==1== Memcheck, a memory error detector
==1== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==1== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==1== Command: ./a.out
==1==
==1== 
==1== HEAP SUMMARY:
==1==     in use at exit: 24,000,000 bytes in 2 blocks
==1==   total heap usage: 27 allocs, 25 frees, 48,006,134 bytes allocated
==1==
==1== LEAK SUMMARY:
==1==    definitely lost: 0 bytes in 0 blocks
==1==    indirectly lost: 0 bytes in 0 blocks
==1==      possibly lost: 24,000,000 bytes in 2 blocks
==1==    still reachable: 0 bytes in 0 blocks
==1==         suppressed: 0 bytes in 0 blocks
==1== Rerun with --leak-check=full to see details of leaked memory

On ubuntu with gcc 13.1 I get similar but half "definitely lost".