On Wed, Dec 20, 2017 at 11:37 PM, Thomas Koenig <tkoe...@netcologne.de> wrote: > Hi Janne, > > I think you need a few more test cases, like (compile with -fcheck=all > and -std=f2018): > > module foo > contains > subroutine f(n) > call g(n-1) > end subroutine f > subroutine g(n) > if (n<0) return > call f(n-1) > end subroutine g > end module foo > program main > use foo > call f(10) > end program main > > Also, there should be a run-time check that the above fails > with -std=f2018, -fcheck=all and the NON_RECURSIVE attribute.
Ok, will do. > However, I am not sure we should make f2018 the default standard as yet, > especially since some things have not yet been ironed out, but I am > open to discussion on that. Seems this is the wrong patch to complain about, since https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01129.html was already committed. :) And also before that, GFC_STD_F2015 (the previous name of GFC_STD_F2018) was an alias for GFC_STD_GNU. So whatever post-F2008 features we have implemented (including the f2008ts stuff) have already been allowed. I think, in general, our current system where -std=gnu means roughly "everything we have implemented so far, except legacy extensions that break standards conformance" is pretty good. As far as I understand N2137 from July 2017 is quite close to the final standard (it's apparently a CD, "candidate draft"); as they are planning publication in 2018 there's not much time left for changes. More info https://wg5-fortran.org/f2018.html . N2141 contains comments on N2137, you can see it's minor edits and clarifications, not any large disagreements. Now, to play devils advocate with my own patch, one can make the case that before making procedures recursive by default we should fix -frecursive / -fmax-stack-var-size so that it's robust in the face of recursion (and multi-threaded access) and also prevents blowing up the stack. See also thread at https://gcc.gnu.org/ml/fortran/2017-12/msg00082.html . My current thinking is to remove -frecursive (keep the option for backwards compatibility, but do nothing), and make -fmax-stack-var-size switch to the heap instead of static memory. Unfortunately I got a bit stuck here, since in trans-decl.c where this is done we no longer have access to the statement block, so there's no place to put the free()'ing of the variable before exiting the scope. Also, how to switch the type to a pointer without breaking anything? So some more invasive surgery is needed. -- Janne Blomqvist
