[PATCH] sparse: add the new m_pos member into struct expression{EXPR_DEREF}

[Oleg Nesterov <oleg@redhat.com>]

Test-case:

	$ cat -n MEMPOS.c
	     1	struct T {
	     2	 int mem;
	     3	} X;
	     4
	     5	void func(struct T *x)
	     6	{
	     7	 x -> mem = 1;
	     8	 X .  mem = 2;
	     9	}

	$ ./test-dissect MEMPOS.c | grep -F T.mem
	   2:6                    def   m T.mem                            int
	   7:4   func             -w-   m T.mem                            int
	   8:4   func             -w-   m T.mem                            int

Note that the reported position of .mem usage is wrong. This is because
do_expression(EXPR_DEREF) uses &expr->pos which is position of TOKEN_SPECIAL,
not the position of the next token (mem).

This also breaks "semind search -l" (search by location)

	$ ./semind add MEMPOS.c
	$ ./semind search -l MEMPOS.c:7:7

reports nothing.

With this patch:

	$ ./test-dissect MEMPOS.c | grep -F T.mem
	   2:6                    def   m T.mem                            int
	   7:7   func             -w-   m T.mem                            int
	   8:7   func             -w-   m T.mem                            int

	$ ./semind add MEMPOS.c
	$ ./semind search -l MEMPOS.c:7:7
	(def) MEMPOS.c	2	6		 int mem;
	(-w-) MEMPOS.c	7	7	func	 x -> mem = 1;
	(-w-) MEMPOS.c	8	7	func	 X .  mem = 2;

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 dissect.c    | 2 +-
 expression.c | 1 +
 expression.h | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/dissect.c b/dissect.c
index 9419c593..a6003afa 100644
--- a/dissect.c
+++ b/dissect.c
@@ -454,7 +454,7 @@ again:
 			p_mode = U_R_VAL;
 		p_type = do_expression(p_mode, expr->deref);
 
-		ret = report_member(mode, &expr->pos, p_type,
+		ret = report_member(mode, &expr->m_pos, p_type,
 			lookup_member(p_type, expr->member, NULL));
 	}
 
diff --git a/expression.c b/expression.c
index 727e7056..b23107da 100644
--- a/expression.c
+++ b/expression.c
@@ -605,6 +605,7 @@ static struct token *postfix_expression(struct token *token, struct expression *
 				break;
 			}
 			deref->member = token->ident;
+			deref->m_pos = token->pos;
 			token = token->next;
 			expr = deref;
 			continue;
diff --git a/expression.h b/expression.h
index 8bf40d32..ce8a29ce 100644
--- a/expression.h
+++ b/expression.h
@@ -202,6 +202,7 @@ struct expression {
 		struct /* deref_arg */ {
 			struct expression *deref;
 			struct ident *member;
+			struct position m_pos;
 		};
 		// EXPR_SLICE
 		struct /* slice */ {
-- 
2.52.0