[Bug fortran/109575] Implement runtime check for valid function result

2023-04-21 Thread sgk at troutmask dot apl.washington.edu via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109575

--- Comment #3 from Steve Kargl  ---
On Fri, Apr 21, 2023 at 08:24:45PM +, anlauf at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109575
> 
> --- Comment #2 from anlauf at gcc dot gnu.org ---
> I have some idea how (and where) the runtime checks need to be implemented,
> but I am confused by the following observations on the occurence of an
> explicit RETURN statement and the use of a RESULT variable:
> 
> __attribute__((fn spec (". ")))
> integer(kind=4) q2 ()
> {
>   integer(kind=4) f;
> 
>   f = 2;
>   return f;
> }
> 
> 
> __attribute__((fn spec (". ")))
> integer(kind=4) g ()
> {
>   integer(kind=4) __result_g;
> 
>   return __result_g;
>   return __result_g;
> }
> 

So, if I follow you correctly, you're worried by about
the two 'return __result_g' versus the one 'return f'?
Dead code elimination likely removes the second 
'return __result_g'.  It indeed seems odd!

[Bug fortran/109575] Implement runtime check for valid function result

2023-04-21 Thread anlauf at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109575

--- Comment #2 from anlauf at gcc dot gnu.org ---
I have some idea how (and where) the runtime checks need to be implemented,
but I am confused by the following observations on the occurence of an
explicit RETURN statement and the use of a RESULT variable:

function f()
  integer :: f
end

function f1()
  integer :: f1
  f1 = 1
end

function q() result (f)
  integer :: f
end

function q2() result (f)
  integer :: f
  f = 2
end

function g()
  integer :: g
  return
end

function g3()
  integer :: g3
  g3 = 3
  return
end

function r() result (f)
  integer :: f
  return
end

function r4() result (f)
  integer :: f
  f = 4
  return
end

While the dump-fortran-original does not show any surprises, the tree-dump
looks somewhat irregular:

__attribute__((fn spec (". ")))
integer(kind=4) f ()
{
  (void) 0;
}


__attribute__((fn spec (". ")))
integer(kind=4) f1 ()
{
  integer(kind=4) __result_f1;

  __result_f1 = 1;
  return __result_f1;
}


__attribute__((fn spec (". ")))
integer(kind=4) q ()
{
  (void) 0;
}


__attribute__((fn spec (". ")))
integer(kind=4) q2 ()
{
  integer(kind=4) f;

  f = 2;
  return f;
}


__attribute__((fn spec (". ")))
integer(kind=4) g ()
{
  integer(kind=4) __result_g;

  return __result_g;
  return __result_g;
}


__attribute__((fn spec (". ")))
integer(kind=4) g3 ()
{
  integer(kind=4) __result_g3;

  __result_g3 = 3;
  return __result_g3;
  return __result_g3;
}


__attribute__((fn spec (". ")))
integer(kind=4) r ()
{
  return;
}


__attribute__((fn spec (". ")))
integer(kind=4) r4 ()
{
  integer(kind=4) f;

  f = 4;
  return f;
  return f;
}


This seems to correspond to two different paths to gfc_generate_return().

[Bug fortran/109575] Implement runtime check for valid function result

2023-04-20 Thread kargl at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109575

kargl at gcc dot gnu.org changed:

   What|Removed |Added

 CC||kargl at gcc dot gnu.org
 Ever confirmed|0   |1
 Status|UNCONFIRMED |NEW
   Last reconfirmed||2023-04-20
   Priority|P3  |P4

--- Comment #1 from kargl at gcc dot gnu.org ---
Change status to "new" as I agree with Harald that this would be a nice runtime
warning for debugging.

Changed to 'P4'