[Bug fortran/64118] New: Strange warning about unused function/subroutine

[Bug fortran/64118] New: Strange warning about unused function/subroutine

[angelo.graziosi at alice dot it]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64118

            Bug ID: 64118
           Summary: Strange warning about unused function/subroutine
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: angelo.graziosi at alice dot it

Created attachment 34144
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34144&action=edit
Tar archive with source code

With the attached tests I get the following warning:

$ gfortran -Wall test_unused_func.f90 -o test_unused_func.out
test_unused_func.f90:54:0: warning: ‘f’ defined but not used
[-Wunused-function]
   real(dp) function f(x) result(y)
 ^

$ gfortran -Wall test_unused_sub.f90 -o test_unused_sub.out
test_unused_sub.f90:44:0: warning: ‘sub3’ defined but not used
[-Wunused-function]
   subroutine sub3()
 ^
test_unused_sub.f90:40:0: warning: ‘sub2’ defined but not used
[-Wunused-function]
   subroutine sub2()
 ^
test_unused_sub.f90:36:0: warning: ‘sub1’ defined but not used
[-Wunused-function]
   subroutine sub1()
 ^


which I find a bit "strange": after all, the function f() in the first test,
for example, is used because it is passed to the call of simpson().. and indeed

$ ./test_unused_func.out
   1.4250604553524227
   1.9202581413298656

confirming it is _used_!

I found this using gfortran from GCC: 4.8.2 (MSYS2 64), 4.8.3 (OSX+MacPorts 64,
Cygwin64), 4.9.1 (MSYS2+MinGW64), but maybe also recent versions of gfortran
are affected.

The tests are archived in the attached tar-ball.

See also the discussion on gfortran mailing list:

https://gcc.gnu.org/ml/fortran/2014-07/msg00168.html
https://gcc.gnu.org/ml/fortran/2014-11/msg00143.html


Ciao,
 Angelo.
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Subject: [Bug rtl-optimization/64010] [msp430-elf] struct function dereference clobbers parameter passed to function
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd010

Peter A. Bigot <pab at pabigot dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pab at pabigot dot com

--- Comment #1 from Peter A. Bigot <pab at pabigot dot com> ---
Since msp430 maintenance is driven by TI and some fixes don't get pushed
upstream promptly see this E2E post for the status of patches within their fork
of gcc:
http://e2e.ti.com/support/development_tools/compiler/f/343/p/384148/1354847.aspx#1354847

At this time there appears to be no publicly available solution.

[Bug fortran/64118] Strange warning about unused function/subroutine

[Joost.VandeVondele at mat dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64118

Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-11-30
                 CC|                            |Joost.VandeVondele at mat dot ethz
                   |                            |.ch
     Ever confirmed|0                           |1

--- Comment #1 from Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> ---
confirmed, looks like the -Wunused-function warning doesn't notice if the
address of a function is taken.


One surprising aspect of this 'trick' of taking addresses of functions is that
it makes private procedures of modules available/callable outside of the
module.

[Bug fortran/64118] Strange warning about unused function/subroutine

[angelo.graziosi at alice dot it]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64118

--- Comment #2 from Angelo Graziosi <angelo.graziosi at alice dot it> ---
In my original test case, if I move the definition of function f(x) before the
subroutine foo(), does not produce warnings. In other words:

  real(dp) function f(x) result(y)
    real(dp), intent(in) :: x
    y = sin(x)
  end function f
  subroutine foo()
    use integrals, only: simpson

    print *, simpson(f, 0.0_dp, 2.0_dp)
    print *, simpson(f, 0.0_dp, 4.0_dp)
  end subroutine foo

DOES NOT produce warnings. Instead:

  subroutine foo()
    use integrals, only: simpson

    print *, simpson(f, 0.0_dp, 2.0_dp)
    print *, simpson(f, 0.0_dp, 4.0_dp)
  end subroutine foo

  real(dp) function f(x) result(y)
    real(dp), intent(in) :: x
    y = sin(x)
  end function f


DORES PRODUCE warnings!

Ciao,
 Angelo.