parquet_get_version Subroutine

    subroutine parquet_get_version(ver_string, mode)
        implicit none
        character(len=:), allocatable, intent(out) :: ver_string !! resulting version string.
        character(len=*), intent(in), optional :: mode
        !! "internal"; absent = default RELEASE_VERSION behavior.
        integer :: i
        character(len=:), allocatable :: preview
        !
! Accept solution from https://stackoverflow.com/questions/31649691/stringify-macro-with-gnu-gfortran
! which provides the easiest way to pass a macro to a string in Fortran complying with both
! gfortran traditional cpp and the standard cpp syntaxes
#ifdef NAGFOR
! NAG drives -fpp, a Fortran preprocessor implementing NEITHER the standard cpp `#`
! stringification operator NOR gfortran's traditional-cpp continuation trick, so no spelling of
! the macro pair below compiles here (confirmed against NAG 7.2: the first gives
! "Invalid character '#'", the second "Unrecognised statement"). Take the release number from
! cversion instead. The consequence is deliberate rather than a gap: the development-build remark
! below compares ver_string against that same substring, so it can never fire under NAG -- the
! question it asks, "did fpm substitute RELEASE_VERSION?", is one this preprocessor cannot answer.
        ver_string = cversion(2:index(cversion, " ") - 1)
#else
#  ifdef __GFORTRAN__
#    define STRINGIFY_START(X) "&
#    define STRINGIFY_END(X) &X"
#  else
#    define STRINGIFY_(X) #X
#    define STRINGIFY_START(X) &
#    define STRINGIFY_END(X) STRINGIFY_(X)
#  endif

        ver_string = STRINGIFY_START(RELEASE_VERSION)
        STRINGIFY_END(RELEASE_VERSION)
#endif
        !
        i = index(cversion, " ")
        !
        if (cversion(2:i-1) /= ver_string) then ! GCOVR_EXCL_START -- gcov attribution artifact
            ! A remark rather than a warning: it says something about how this copy of the library
            ! was BUILT, not about the caller's data, and it fires on every call in a build whose
            ! macro substitution did not happen. So it goes through the informational channel, which
            ! `verbosity="silent"` quiets while leaving real warnings alone.
            call parquet_emit_info("note: this is a development build of parquet-fortran " // &
                "(library version " // trim(cversion) // ", RELEASE_VERSION " // trim(ver_string) // ")")
        end if ! GCOVR_EXCL_STOP
        !
        if (present(mode)) then
            select case (mode)
            case ("internal")
                ver_string = trim(cversion)
            case default
                ! Only a short preview of the offending value goes into the message, never the whole
                ! (unboundedly long) text: ifx 2026.1.1's ERROR STOP runtime corrupts memory once the
                ! composed message reaches 8192 bytes, and `mode` is caller-supplied with no cap.
                if (len(mode) > 100) then
                    preview = mode(1:100) // "..."
                else
                    preview = mode
                end if
                error stop "parquet_get_version: invalid mode '" // preview // &
                    "' (must be 'internal'; for the linked Arrow/Parquet C++ library versions " // &
                    "call parquet_get_arrow_version)"
            end select
        else
            ver_string = trim(ver_string)
        end if
        !
    end subroutine parquet_get_version