Dear Member of the OCaml mailing list,

The problem about which I reported on this reflector around two weeks ago 
(array index violation after around 4 days) has in the mean time been 
solved thanks to the great native function call backtrace for the ocamlopt 
compiler due to Markus Mottl. Given that my program crashed after 3.7 
days, and my program ran around 30x slower in byte code, debugging using 
byte code was not an option (this slowdown had been similar if I had used 
_DEBUG mode of a C++ program instead of _RELEASE version). Also, as 
reported earlier, putting "try ... with " around all attempts to index an 
array is not feasbile in standard OCaml for array elements in the left 
hand sides of assignments. A static unhandled exception checker provided 
on a web page, ran into dead HTML links. 

Hence, the native function call, which comes at minimal runtime overhead 
cost, mainly the cost of -inline 0, is a great new feature that would give 
OCaml another advantage over C++ when added to the OCaml language in a 
next release. Below I give a toy example :

--- nlv13512/TestProgram ---> ls
attempt.ml*
--- nlv13512/TestProgram ---> cat att*
let a = Array.make 2 0;; 
let f i = i*i;; 
let g i = a.(i);; 
let b = f 2;;
let c = g 2;; 
--- nlv13512/TestProgram ---> ocamlopt -inline 0 -gb attempt.ml
--- nlv13512/TestProgram ---> a.out
Fatal error: exception Invalid_argument("index out of bounds")
Native function backtrace:

  camlAttempt__g_60
  camlAttempt__f_58
--- nlv13512/TestProgram ---> 

=Andries

PS The attached patch was provided to me by Markus Mottl for the 3.09.1. 
release. 




------------------------------------------------------------------------
Dr. Ir. Andries P. Hekstra
Philips Research 
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Tel./Fax/Secr. +31 40 27 42048/42566/44051 
   *  Good open source anti-RSI software : http://www.workrave.org