[m-rev.] for review: fix bug #196: binary compatiblity checks in C grade don't work

[Julien Fischer]

Hi Zoltan,

On Thu, 14 Jul 2016, Zoltan Somogyi wrote:

> On Fri, 15 Jul 2016 01:16:25 +1000 (AEST), Julien Fischer <jfischer at opturion.com> wrote:
>> Is anyone intending to review this one?  In the absence of any comments
>> I'll commit it later today.
>
> I thought I already reviewed the idea, and said that I would prefer
> to fix the problem by exporting a function that refers to the value
> of MR_GRADE_VAR. I think this would be more robust in the face
> of compiler optimizations, though it does have the slight downside
> of adding one symbol per module to the executable's symbol table.

The latter was essentially my objection to your suggestion; however
having just looked at the size of the symbol table for "hello world"
on my system (~10,800 entries), adding another 115 + the number of
modules in my program isn't going to make much difference.

I'll go ahead and implement your approach instead.  (To follow up my
original post, I'll note that the issue does not appear to affect
MSVC.)

Julien.