Re: [GHC] #8371: ghci byte compiler + FFI crashes when used with embedded R

28 Sep 2013

      I hope my last two postings to ghc-devs did not create too much noise,
as I intended them to go to a comment thread in ghc-tickets (I realize
now that I need to do this outside of gmail).

It appears that replies to comments in ghc-tickets from gmail are
automatically routed to ghc-devs, potentially showing comments
out of context. Sorry.

Dominick

On Sat, Sep 28, 2013 at 10:35 AM, Dominick Samperi wrote:
...
After further testing it appears this work-around is not enough.
It needs to be combined with another suggestion in this
thread: must use ghc-7.7. There is a segfault (but no
"C stack usage" message) when ghc-7.6.3 is used.
Thank you!
On Sat, Sep 28, 2013 at 10:08 AM, Dominick Samperi wrote:
...
Thanks! Turning off R's stack limit checks will not work. I tried this
and this leads to a segfault. Fortunately, your experiments led me
to a work-around: simply use the -fno-ghci-sandbox flag.
R is not thread-safe, and this flag tells ghci to run computations
in the main thread instead of forking.
On Sat, Sep 28, 2013 at 1:29 AM, GHC  wrote:
...
#8371: ghci byte compiler + FFI crashes when used with embedded R
-------------------------------+----------------------------------
        Reporter:  dsamperi    |            Owner:
            Type:  bug         |           Status:  new
        Priority:  normal      |        Milestone:
       Component:  GHCi        |          Version:  7.6.3
      Resolution:              |         Keywords:
Operating System:  Linux       |     Architecture:  x86_64 (amd64)
 Type of failure:  GHCi crash  |       Difficulty:  Unknown
       Test Case:              |       Blocked By:
        Blocking:              |  Related Tickets:
-------------------------------+----------------------------------
Comment (by rwbarton):
I can reproduce this without ghci, by putting a forkIO around the body
of
 main (and adding a threadDelay in the main thread).
It seems to just be an interaction between R's method for determining
the
 base address of the stack and the way pthread allocates stacks for new
 threads. Try this C example program `pt.c`.
{{{
 #include 
 #include 
 #include 
int Rf_initEmbeddedR(int argc, char **argv);
void *foo(void *blah)
 {
     char *args[] = {"pt", "--gui=none", "--silent", "--vanilla"};
     int r;
     setenv("R_HOME", "/usr/lib/R", 1);
     r = Rf_initEmbeddedR(sizeof(args)/sizeof(args[0]), args);
     printf("r = %d\n", r);
 }
int main(void)
 {
     pthread_t tid;
     pthread_create(&tid, NULL, foo, NULL);
     while (1)
         sleep(1);
     return 0;
 }
 }}}
{{{
 rwbarton@adjunction:/tmp$ gcc -o pt pt.c  -lpthread -lR
 rwbarton@adjunction:/tmp$ ./pt
 Error: C stack usage is too close to the limit
 Error: C stack usage is too close to the limit
 r = 1
 }}}
It would probably be best to just disable R's stack limit checks, if
 possible.
--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8371#comment:6
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