[R] Mysterious seg fault.

[Peter Langfelder]

Segfaults are not always repeatable. You may have an undefined pointer that
sometime points into unreachable or unallocated memory, causing a segfault,
and sometimes may point into valid memory, without causing a segfault.

You may want to read
https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Checking-memory-access
for tips on how to diagnose such problems.

HTH,

Peter

On Sat, Aug 11, 2018 at 2:13 PM Rolf Turner <r.turner using auckland.ac.nz> wrote:

>
> I am getting a seg fault from a package that I am working on, and I am
> totally flummoxed by it.  The fault presumably arises from dynamically
> loaded Fortran code, but I'm damned if I can see where the error lies.
>
> In an effort to diagnose the problem I created a "non-package" version
> of the code.  That is, I copied all the *.R files and *.f file into a
> new directory.  In that directory I created a *.so file using
> R CMD SHLIB.
>
> In the R code I removed all the "PACKAGE=" lines from the calls to
> .Fortran() and put in appropriate dyn.load() calls.
>
> I then started R in this new "clean" directory and sourced all of the
> *.R files.
>
> I then issued the command that produces the seg fault when run under the
> aegis of the package.  The command ran without a murmur of complaint.
> WTF?
>
> Can anyone suggest a reason why a seg fault might arise when the code is
> run in the context of a package, but not when it is run in "standalone
> mode"?
>
> I have checked and rechecked my init.c file --- which is the only thing
> that I can think of that might create a difference --- and cannot find
> any discrepancy between the declarations in the init.c file and the
> Fortran code.
>
> The package is a bit complicated, so giving more detail would be
> cumbersome.  Also I have no idea what aspects of detail would be
> relevant.  If anyone would like more info, feel free to ask.
>
> I would really appreciate it if someone could give me some suggestions
> before I go *completely* mad!
>
> cheers,
>
> Rolf Turner
>
> --
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
>
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