Forw: Question about mudflap

["Frank Ch. Eigler" <fche at redhat dot com>]

Date: Wed, 16 Nov 2005 03:20:54 -0500
From: "Doug Graham" <dgraham@nortel.com>
To: "Frank Ch. Eigler" <fche@redhat.com>
Subject: Question about mudflap

Hi,

Not sure whether I should report this as a bug or not, because there
might be something going on that I don't understand.

What I'm wondering is whether or not mudflap should instrument accesses
to globals that it doesn't know the size of.  In the following code:

   extern int global[];
   
   int main(void)
   {
     printf("%d\n", global[3]);
     global[5] = 42;
   }

Mudflap does not emit any __mf_check calls.  It does warn during
compilation:

  t4-1.c:10: warning: mudflap cannot track unknown size extern 'global'

and I understand that, but I don't understand why this would prevent
it from checking accesses to the array.  Is that a deliberate design
decision, or a bug?  I'd much prefer if it did go on and check all
accesses to the array because in my case, global[] will always be
registered by the compilation unit in which it is defined.  It's pretty
common to have extern decls whose sizes aren't known.

Thanks,
Doug.