Problem with instrumenting GIMPLE for adding a global variable

[Prateek Saxena <prateeksaxena@gmail.com>]

Hi,

I am trying to implement a prototype pass that instruments a function
to check for safe memory accesses. As a starting point I looked at
mudflap1 pass, in tree-mudflap.c and decided that I should write a
dummy pass ( very simple, but similar to mudflap) that instruments the
code to count the number of functions in the source file.

I am unable to add a global variable in the file scope. The global
VAR_DECL building function looks like this:

{
  tree decl = build_decl (VAR_DECL, get_identifier ("my_var"),
integer_type_node);
  TREE_PUBLIC (decl) = 0;
  DECL_EXTERNAL (decl) = 0;
  TREE_STATIC (decl) = 1; 
  gimplify_stmt (my_variable);
  lang_hooks.decls.pushdecl (decl);
  return decl;
}

It is called from within my call-back function "execute_my_pass" ( as
specified by me in the tree_opt_pass structure ).

I increment  "my_var" in every function. But, the instrumented object
file doesnot have a storage allocated for this variable in the .data
section. The problem is that DECL_CONTEXT of this VAR_DECL is always
getting assigned to a function, and not to global file scope. Why is
that?

Any help would be appreciated.

Thanks,
Prateek.