Hi Krishna,
On 03.04.21 13:52, Krishna Kariya wrote:
I am Krishna, a final-year undergraduate student from India. I am
interested in the project “Fortran – run-time argument checking” for
GSoC 2021. Please share some resources about the project. Please point
to some issues or programming tasks that I can try out to understand
the project better.
In older Fortran program, no modules were used and, hence, no argument
checking was possible. Think of:
subroutine caller()
external callee
integer :: A(5), b(4)
call callee(A, B, 5.0, "Hello")
end
Here, the compiler only knows that 'callee' is a subroutine but has no
idea about the actual arguments. Alternatively, in semi-modern code, it
could use:
subroutine caller()
integer :: A(5), b(4)
interface
subroutine callee(w,x,y,z)
integer :: w(*), x(*)
real :: y
character(*) :: z
end
end interface
call callee(A, B, 5.0, "Hello")
end
The idea is that the caller now fills global variables:
__gfortran_called_proc = callee ! function pointer
__gfortran_called_interface = ... pointer to a struct/derived type
and afterwards, it would set both to null.
The latter contains then:
- a version number (to be able to add more data later on)
- file name, function name and line number of the caller
- information about the arguments:
- 4 arguments
- first: integer array of size 4
- ...
And in
subroutine callee(....)
it would check:
if (__gfortran_called_proc == callee)
and then fill a similar struct with similar data
(version number, filename, proc name, line number, arguments)
and then call the library function
__libgfortran_check_args(
__gfortran_called_interface,
callee_interface);
which then checks whether the arguments match.
Internal procedures and module procedures can be excluded as
those can not be access from the outside.
Minimal check would be:
- number of arguments
- data type
- array + array size
- caller/callee is a function – and expected return values (type, array)
but that can be extended especially in the context of an interface block
(with a zoo of attributes, additional array types etc.) and with intent
handling (intent(out) in caller but constant or intent(in) as argument,
intent(out) argument to intent(in) etc.)
Tobias
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