https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109500
--- Comment #4 from anlauf at gcc dot gnu.org ---
I think one cannot achieve what the OP wants by using allocable function
results. One should use a subroutine instead.
Compiling the code with the NAG compiler gives:
NAG Fortran Compiler Release 7.1(Hanzomon) Build 7101
Warning: pr109500.f90, line 7: Allocatable function F has not been allocated or
assigned a value
Error: pr109500.f90, line 2: Expected an ALLOCATABLE variable for argument P
(no. 1) of IS_ALLOCATED
[NAG Fortran Compiler error termination, 1 error, 1 warning]
Not perfect, but what you are seeing is an attempt by the compiler to do
argument association when you invoke function is_allocated.
Now look at the following variants in the main:
1)
print *, allocated(f())
You'll get:
2 | print *, allocated(f())
| 1
Error: 'array' argument of 'allocated' intrinsic at (1) must be a variable
This is what the standard says.
2)
integer, allocatable :: p
p = f()
print *, allocated(p)
This compiles, but you get a runtime error (SIGSEGV) with gfortran and ifort.
Why? The assignment p=f() is invalid for unallocated r.h.s., and you are
hitting this. The running program will never reach the allocated(p).
I don't see a legal way to use an allocatable function without allocating
the result. So you should use a subroutine and allocate a result variable.
The only potential issue I see here with gfortran is that there is no working
runtime diagnostics for the non-allocated r.h.s. above. But there is none
for current ifort/ifx either.
If the reporter agrees, we should close this PR as invalid.
