[R] Mysterious seg fault --- SOLVED

peter dalgaard pd@|gd @end|ng |rom gm@||@com
Mon Aug 13 13:39:30 CEST 2018

It's odd, possibly a bug, that you don't get 

Error: object 'nphi' not found

but I can't offhand see where the evaluation of args to .C/.Fortran is supposed to take place.


> On 13 Aug 2018, at 11:54 , Rolf Turner <r.turner using auckland.ac.nz> wrote:
> On 13/08/18 20:45, Henrik Bengtsson wrote:
>> On Mon, Aug 13, 2018 at 3:51 AM Rolf Turner <r.turner using auckland.ac.nz> wrote:
>>> OK everybody!  You can relax.  :-) I managed to spot the loony.  After
>>> mucking around with valgrind, and before trying gdb, I had one more look
>>> at my code and *finally* saw the stupid thing that I had been doing.
>>> In the call to .Fortran() I had a line
>>>      nphi=as.integer(nphi),
>>> but "nphi" was nowhere defined (!!!) in the R code.  The name "nphi"
>>> appeared as an argument in the Fortran subroutine in question, but was
>>> nowhere actually *used*!!!
>> Didn't R CMD check pick this up, that is, didn't it report that 'nphi'
>> is a "global" variable?
> No it didn't.  The name only appears in the call to .Fortran().  I think if it appeared in a call to an ordinary garden-variety R function then a warning would have been issued.
> Such a lapse would be hard for R CMD check to pick up.  E.g
>   nphi=integer(1),
> would be OK in a call to .Fortran (which would allow a value of nphi, calculated within the called subroutine, to be *returned*) whereas
>   nphi=as.integer(nphi),
> causes trouble when nphi has never been defined (as I found out after a great expenditure of time and torn-out hair).  In the former instance it doesn't matter an FTCF whether nphi has been defined or not.
> cheers,
> Rolf
> -- 
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Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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