The errstat allows us to simplify the Fortran-style error handling.
In the Fortran-style error handling, a status code and message of
a processing result is acquired as intent(out) arguments, like
real(real32), allocatable :: f(:)
integer(int32) :: stat
character(128) :: msg
allocate (f(10))
allocate (f(10), stat=stat, errmsg=msg)
if (stat /= 0) then
print *, "an error occurred: ", msg
end ifCompile the above with some Fortran compilers and run the executables; the results are
an error occurred: Attempt to allocate an allocated object(gnu gfortran)
an error occurred: allocatable array is already allocated (intel fortran)
an error occurred: 割付け変数が割付け済みです (nag fortran)
For user-defined procedures, it is troublesome to add optional arguments for the status code and message and to write if statements to branch according to those existing or not.
function inverse(x, stat, msg) result(y)
use, intrinsic :: iso_fortran_env
use, intrinsic :: ieee_arithmetic
implicit none
real(real64) :: x
integer(int32), intent(out), optional :: stat
character(:), allocatable, intent(out), optional :: msg
real(real64) :: y
y = 1d0/x
if (ieee_is_nan(y)) then
if (present(stat)) stat = 1
if (present(msg)) msg = "the result is not-a-number"
return
end if
if (.not. ieee_is_finite(y)) then
if (present(stat)) stat = 2
if (present(msg)) msg = "the result is infinite"
return
end if
if (present(stat)) stat = 0
if (present(msg)) msg = ""
end function inverseThe errstat simplifies the if statements as below:
if (ieee_is_nan(y)) then
call catch_status(1, "the result is not-a-number", stat, msg)
return
end if
if (.not. ieee_is_finite(y)) then
call catch_status(2, "the result is infinite", stat, msg)
return
end if
call catch_status(success_status_code, success_status_msg, stat, msg)Not only the simplification of the if statements but also the error handling on the caller becomes clearer.
y = inverse(0d0, stat, msg)
if (is_status(stat, statuses%error_occurred)) then
print *, msg
end ifThe errstat also provides a user-defined derived type error_stat_type that combines the stat and msg.
The error handling can be more simplified.
if (ieee_is_nan(y)) then
call catch_error(1, "the result is not-a-number", stat)
return
end if
if (.not. ieee_is_finite(y)) then
call catch_error(2, "the result is infinite", stat)
return
end if
call set_success(stat) type(error_stat_type) :: stat
y = inverse(1d0, stat)
if (error_occurrd(stat)) then
print *, stat%get_message()
end if- A Fortran compiler
- The library is tested using gfortran 11.2.0, intel fortran 2021.5, and nag fortran 7.1 on Windows 10.
- fpm
- The library supports fpm (fortran-lang/fpm) for build. fpm 0.7.0, alpha is used.
- FORD (optional)
- FORD is used for generating the API document.
To get the code, execute the following commnad:
git clone https://github.com/degawa/errstat.git
cd errstat
To build the library using fpm, execute the following command:
fpm build
The API documentation can be generated using FORD.
ford api-doc-ford-settings.md
To use the errstat in your fpm project, add the following to fpm.toml.
[dependencies]
errstat = {git = "https://github.com/degawa/errstat"}