Re: Moving smatch to use sparse

["Dan Carpenter" <error27@gmail.com>]

Sparse reads the source and creates a parse tree.  At the base, are
function symbols, the function has a bunch statements and the
statements have a bunch of expressions which branch out into even more
expressions.  If you have data that's a symbol.

struct expression is defined in expression.h
struct symbol is defined in symbol.h
struct statement is in parse.h

The important functions are:
set_state(name, my_id, sym, ISNULL);
get_state(deref, my_id, sym)
set_true_false_states(left, my_id, sym_left, ISNULL, NONNULL);
add_hook(&match_assign, ASSIGNMENT_HOOK);
void register_your_check(int id)
left = get_variable_from_expr(expr->left, &sym_left);
left = alloc_string(left);

my_id is a different int for every check script.
sym is a symbol * to the sparse symbol.
The condition hook feeds you one condition at a time.
add_hook() sets up a call back that will be called for every
assignment in this case.
add the register_your_check() to smatch.c.
get_variable_from_expr() is a bit buggy still but it's supposed to
give a string representation of an expression and it also gives you a
symbol pointer.  If you want to keep the string instead of just
printing it out or using it for get_state() then you have to call
alloc_string().

I haven't added setting up custom merge_rules yet.  Will do.

Internally smatch_states are a struct.  I'm going to add some more
fields to that so it might be useful to have a get_state_struct()
function...

smatch_flow.c interprets that sparse tree.  If you want to add another
hook that's the place to do it.

That's pretty much it.

regards,
dan carpenter