#include <cstdlib>

int main(int argc, char** argv) {
  int* ptr = NULL;
  *ptr = 1;

  exit(EXIT_SUCCESS);
}

Referencing that NULL pointer obviously crashes straight away with a terse segmentation fault:

By simply linking it with libSegFault, which seems to be documented only very informally, but comes with glibc:

Of course you could get all this by starting the program with gdb but this looks like a great technique for diagnosing crashes “in the wild”. Not that my code segfaults all the time, mind! After writing this, I found some more details on Stack Overflow, including a good tip about c++filt. Another useful utility is addr2line.

Also I am starting to incorporate libtap++, an implementation of the Test Anything Protocol, into my projects. C++ has strong typing, at least stronger than plain C, which helps trap errors at compile time like in OCaml. But since I always write a test harness anyway, it makes sense to fall into line with the way everyone else does it, especially as I have ambitions for wider adoption of my bindings†. Presently there is no TAP producer for OCaml‡, so at some point I will work on that too (or just bind to the C libtap).

On the recommendation of a friend of mine who is a very experienced C++ programmer, I have been playing with Eclipse CDT, which is pretty nice for C/C++ but doesn’t deal well at all with mixed C++/OCaml projects, and EclipseFP seems to have dropped support for OCaml at some point. I think I’ll try using it for just the .so portion of my projects and stick with Emacs/make for final integration with OCaml bindings, at least until I see if it really is more productive to do C++ in a full-blown IDE versus good old Emacs. Also I’ve bought a copy of The Boost C++ Libraries, again on the recommendation of my friend, that whatever I want, it’s probably already in Boost.

† OPERATION FOOTHOLD
‡ See comments

Or too little too late, I’ve already switched to Emacs :-)

open Printf
  
let _ =
  let array_max arr =
    let arr' = Array.copy arr; 
    Array.sort (fun a b -> b - a) arr';
    arr'.(0) in
  printf "max=%d\n" (array_max [|1;2;3;4;5|])

To me as a beginner this looks quite plausible, since I wrote something much like it, of course it should actually be:

   let arr' = Array.copy arr in

But the error from the compiler is strange:

make -k 
ocamlc -g -c testcase.ml
File "testcase.ml", line 9, characters 0-0:
Error: Syntax error
make: *** [testcase.cmo] Error 2
make: Target `testcase' not remade because of errors

That is actually one character beyond the end of my file!

So my top tip for today is, mysteriously vague error messages like this are probably a ; instead of an in somewhere. Emacs to the rescue:

M-x replace-regexp RET \(let.*\); RET \1 in RET

Hah! Now if only I could think of a way to invoke that automagically when I get 0-0 after C-c C-c…

1. Download Folding Mode and save folding.el in the Emacs site lisp directory (on my Debian machine that is /usr/share/emacs23/site-lisp/, probably the same on any Linux). Surprisingly there’s no .deb package for it or apt-get install emacs-goodies-el.
2. Add the following to your ~/.emacs:

   (load "folding" 'nomessage 'noerror)
   (folding-add-to-marks-list 'haskell-mode "--{{{"  "--}}}"  nil t)
   (folding-mode-add-find-file-hook)
   (add-hook 'haskell-mode-hook 'folding-mode)
   
   (folding-add-to-marks-list 'tuareg-mode "(*{{{"  "(*}}}*)"  nil t)
   (add-hook 'tuareg-mode-hook 'folding-mode)
   

   Lines 4 and 7 cause folding-mode to be automatically entered after haskell-mode or tuareg-mode respectively, which seems to be necessary, rather than just loading it on Emacs startup with auto-load. This is slightly different from the instructions on the page, perhaps it was written for an older Emacs.

3. Delimit the code with the appropriate markers. These can be anything you put in .emacs, {{{ and }}} in conjunction with the language’s own comment characters seems to be a convention. Unfortunately Emacs doesn’t seem to be able to do this automagically the way other language-sensitive editors would (then again, those editors don’t allow you to define folding positions yourself, they always do it on functions or other obvious blocks)

As an example you can then toggle between:

And:

With right-click.