lotto@lamia.harvard.edu (Jerry Lotto) (06/06/90)
I would appreciate pointers to any people or documentation that might
help me work out a problem. I am not really trying to do general
recursion... there is a single calling stack that may need to repeat
once within its own context. The problem I am having is with calling
args -> ie:
A -> B(foo1, foo2) -> C(var1, var2) -> D(var1, var2) -> E ->
B(bar1, bar2) -> C(var1, var2) -> D(var1, var2)
Everything is fine until we return from E. Now the addresses D\var1
and D\var2 are screwed up (the same as E\bar1 and E\bar2) whereas the
addresses of C\var1, C\var2, B\var1, and B\var2 are correct (that of
A\foo1 and A\foo2). I would like to protect the argument stacks so
that all of the variables are properly restored upon return from E.
Any help would be greatly appreciated. AdThanksvance.
--
Jerry Lotto <lotto@lhasa.harvard.edu> "Have you hugged the curves today?"
Chemistry Dept., Harvard Univ. AMA #520019 DoD #018 HOG #0323880bethge@wums2.wustl.edu (Paul H. Bethge) (06/13/90)
VMS Fortran (like most Fortrans) does *not* in general support recursion, although it sometines works for simple cases. The problem is that for some kinds of arguments, a temporary copy is made of the argument address, and the argument is addressed via the temporary rather than via the argument list. Other temporaries may also be generated, depending on the code. The temporaries are statically allocated, not on the stack, so they get overwritten if the routine is called recursively. There is not much you can do about this. _____________________________________________________________________ Paul H. Bethge bethge@wums.wustl.edu Biochemistry, Box 8231 bethge@wums.bitnet Washington University St. Louis, MO 63110 314-362-3354
khb@chiba.Eng.Sun.COM (Keith Bierman - SPD Advanced Languages) (06/13/90)
In article <3661.267509f4@wums2.wustl.edu> bethge@wums2.wustl.edu (Paul H. Bethge) writes:
VMS Fortran (like most Fortrans) does *not* in general support
recursion, although it sometines works for simple cases. The problem
....
I think that *most* fortrans probably do. Unix platforms usually do,
and some of the PC compilers allow it also. Between MSDOS and Unix
you have *most* if you are counting heads or vendors.
cheers (from the uk)
--
Keith H. Bierman |*My thoughts are my own. !! kbierman@Eng.Sun.COM
It's Not My Fault | MTS --Only my work belongs to Sun* khb@chiba.Eng.Sun.COM
I Voted for Bill & | Advanced Languages/Floating Point Group (415 336 2648)
Opus | "When the going gets Weird .. the Weird turn PRO"seymour@milton.acs.washington.edu (Richard Seymour) (06/14/90)
In article <KHB.90Jun13075104@chiba.Eng.Sun.COM> khb@chiba.Eng.Sun.COM (Keith Bierman - SPD Advanced Languages) writes: >In article <3661.267509f4@wums2.wustl.edu> bethge@wums2.wustl.edu (Paul H. Bethge) writes: >> VMS Fortran (like most Fortrans) does *not* in general support >> recursion, although it sometines works for simple cases. The problem >>.... >I think that *most* fortrans probably do. Unix platforms usually do, >and some of the PC compilers allow it also. Between MSDOS and Unix >you have *most* if you are counting heads or vendors. Just because lots of people do it, does not mean it's correct. To Quote ANSI x3.9-1978 Fortran 77 Standard sect 15.6.2.2 (page 15-10) (both subset and full standard): "A subprogram must not reference itself, either directly or indirectly." That's MUST NOT. and "indirectly" can be loosely translated to: by sneaky means such as calling something which calls the caller. (Raytheon's Fortran for their 704 computer (in 1972 or thereabouts) had a /r switch to allow recursion. Just because i used it did not mean that it was a good idea (and it really confused other people)). --dick
mikel@pyrps5 (Mike Lipsie) (06/14/90)
In article <4108@milton.acs.washington.edu> seymour@milton.u.washington.edu (Richard Seymour) writes: > > "A subprogram must not reference itself, either directly or indirectly." > >That's MUST NOT. and "indirectly" can be loosely translated to: by > sneaky means such as calling something which calls the caller. It seems that it is time yet again to remind the readers of this group of a feature of the Fortran standard that is a bit different than those of other languages. The standard is for Fortran _programs_, not compilers. A correct compiler is one that will compile a correct program. In the quote above, any program that does call itself (directly or indirectly) is not a correct Fortran 77 program. A compiler is allowed to do anything it wants to an incorrect program, including letting it work or letting it fail in a quiet, insidious manner. ----------- Mike Lipsie mikel@pyramid.com Pyramid Technology Corp, Mountain View, CA +1 415 335 8657 "Toto kansasoseum non est cognito" -- Phil Frank