Re: [PATCH] Fortran: fix reallocation on assignment of polymorphic variables [PR110415]

[Tobias Burnus <tobias@codesourcery.com>]

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Hi Andrew,

On 20.11.23 14:56, Andrew Jenner wrote:
> This patch adds the testcase from PR110415 and fixes the bug.

Thanks. I can confirm experimentally that it fixes the original PR.  However, if I extend
the original testcase (-2), it fails with run with valgrind or when run with -fsanitize=address.

The array testcase (-3) seems to be fine with and without your patch.

I think it makes sense to include both extended testcases and put them under
gcc/testsuite/gfortran.dg/asan/ to ensure ASAN checks for leaks and some invalid memory access.

I still should have a closer look at the -ftree-dump-original and at the patch itself.

* * *

For the '-2' testcase, ASAN (-fsanitize=undefined) shows:

==11823==ERROR: AddressSanitizer: heap-use-after-free on address 0x608000000220 at pc 0x000000405d39 bp 0x7ffcfa6eef50 sp 0x7ffcfa6eef48
WRITE of size 96 at 0x608000000220 thread T0
     #0 0x405d38 in __copy_MAIN___D gcc/testsuite/gfortran.dg/pr110415.f90:5
     #1 0x404dc0 in MAIN__ gcc/testsuite/gfortran.dg/pr110415.f90:24
     #2 0x40a82b in main gcc/testsuite/gfortran.dg/pr110415.f90:28
     #3 0x7f1e2a4281af in __libc_start_call_main (/lib64/libc.so.6+0x281af) (BuildId: bbeee08e5f56966e641c4f3ba4ea1da9d730d0ab)
     #4 0x7f1e2a428278 in __libc_start_main@@GLIBC_2.34 (/lib64/libc.so.6+0x28278) (BuildId: bbeee08e5f56966e641c4f3ba4ea1da9d730d0ab)
     #5 0x402274 in _start ../sysdeps/x86_64/start.S:115

0x608000000220 is located 0 bytes inside of 96-byte region [0x608000000220,0x608000000280)
freed by thread T0 here:
     #0 0x7f1e2b4daf35  (/lib64/libasan.so.8+0xdaf35) (BuildId: 3e1694ad218c99a8b1b69231666a27df63cf19d0)
     #1 0x404d1c in MAIN__ gcc/testsuite/gfortran.dg/pr110415.f90:24
     #2 0x40a82b in main gcc/testsuite/gfortran.dg/pr110415.f90:28
     #3 0x7f1e2a4281af in __libc_start_call_main (/lib64/libc.so.6+0x281af) (BuildId: bbeee08e5f56966e641c4f3ba4ea1da9d730d0ab)

previously allocated by thread T0 here:
     #0 0x7f1e2b4dc03f in malloc (/lib64/libasan.so.8+0xdc03f) (BuildId: 3e1694ad218c99a8b1b69231666a27df63cf19d0)
     #1 0x4042d2 in MAIN__ gcc/testsuite/gfortran.dg/pr110415.f90:22
     #2 0x40a82b in main gcc/testsuite/gfortran.dg/pr110415.f90:28
     #3 0x7f1e2a4281af in __libc_start_call_main (/lib64/libc.so.6+0x281af) (BuildId: bbeee08e5f56966e641c4f3ba4ea1da9d730d0ab)

* * *

Tobias
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! { dg-do run }
!
! Contributed by Brad Richardson <everythingfunctional@protonmail.com>
!
implicit none
  type, abstract :: p
    integer :: a = 4
  end type p

  type, extends(p) :: c
    integer :: b = 7
    character(len=:), allocatable :: str, str2(:)
  end type c

  type, extends(p) :: d
    integer :: ef = 7
    character(len=:), allocatable :: str, str2(:)
  end type d

  class(p), allocatable :: a

  a = func()

  a = func2()

  a = func()

  deallocate(a)

contains
  function func2() result(a)
    class(p), allocatable :: a
    a = d()
  end function func2

  function func() result(a)
    class(p), allocatable :: a

    a = c()
    select type(a)
    type is (c)
      a%str = 'abcd'
      a%str2 = ['abcd','efgh']
    end select
  end function func
end program

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! { dg-do run }
!
! Contributed by Brad Richardson <everythingfunctional@protonmail.com>
!
implicit none
  type, abstract :: p
    integer :: a = 4
  end type p

  type, extends(p) :: c
    integer :: b = 7
    character(len=:), allocatable :: str, str2(:)
  end type c

  type, extends(p) :: d
    integer :: ef = 7
    character(len=:), allocatable :: str, str2(:)
  end type d

  class(p), allocatable :: a(:)

  a = func()

  a = func2()

  a = func()

  deallocate(a)

contains
  function func2() result(a)
    class(p), allocatable :: a(:)
    a = [d(),d()]
  end function func2

  function func() result(a)
    class(p), allocatable :: a(:)

    a = [c(),c(),c()]
    select type(a)
    type is (c)
      a(1)%str = 'abcd'
      a(2)%str = 'abc'
      a(3)%str = 'abcd4'
      a(1)%str2 = ['abcd','efgh']
      a(2)%str2 = ['bcd','fgh']
      a(3)%str2 = ['abcd6','efgh7']
    end select
  end function func
end program