Le 22/08/2013 23:30, Mikael Morin a écrit : > Le 14/08/2013 23:46, Thomas Koenig a écrit : >> Hello world, >> >> the attached patch enables more sophisticated bounds-checking on >> array slices by using gfc_dep_difference to calculate extents. >> The information may also be useful in other places of the >> front end, I don't really know. >> >> There is one wrinkle (alluded to in the comments) which makes >> this harder. When somebody changes the value of a variable >> used in detemining the size of an array, such as >> >> subroutine foo(a,n) >> real, dimension(n) :: a >> >> n = n -2 >> >> print *,ubound(a(n-1:)) >> >> we cannot compare n-1 against n and think that their difference is >> one :-( >> >> This is why I restricted myself to expressions where all >> indices are specified, e.g. in a(n+1:n+4) or none are specified, >> as in a(:). >> >> In order for this to work on 64-bit systems, it was necessary >> to look through widening integer conversions, so I added that >> functionality to discard_nops. Using this function in >> gfc_dep_compare_expr made this function shorter and cleaner. >> >> Regression-tested. OK for trunk?
OK. By the way, it seems that arg1 and arg2 declarations should be removed in gfc_dep_compare_expr. >> > This looks mostly good. The dependency.c cleanup is nice, I have yet to > understand what the 'end == NULL' condition is for. I come back to you > soon. > For what it's worth, 'end' is non-NULL in only one place and there the gfc_ref_dimen_size result is discarded. Thus its handling should better be inlined or have its own function separate from gfc_ref_dimen_size. It seems to be a lot of trouble for little gain though. Mikael
