fix assignment check with function attribute

It's OK to assign a non-qualified type to the corresponding
const- or -volatile-qualified type (same for 'restrict').
For modifiers like __pure or __noreturn, it's the opposite:
it's OK to assign the qualified version to the corresponding
non-qualified type.

Allow this by using type_difference() with the appropriate mask
when checking assignments.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

2 files changed, 8 insertions, 2 deletions

diff --git a/evaluate.c b/evaluate.c
index b9d3cfe3..863750fa 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -658,7 +658,7 @@ static struct symbol *evaluate_ptr_add(struct expression *expr, struct symbol *i
 
 static void examine_fn_arguments(struct symbol *fn);
 
-#define MOD_IGN (MOD_QUALIFIER | MOD_PURE)
+#define MOD_IGN (MOD_QUALIFIER | MOD_FUN_ATTR)
 
 const char *type_difference(struct ctype *c1, struct ctype *c2,
 	unsigned long mod1, unsigned long mod2)
@@ -1429,6 +1429,7 @@ static int check_assignment_types(struct symbol *target, struct expression **rp,
 
 	if (tclass == TYPE_PTR) {
 		unsigned long mod1, mod2;
+		unsigned long modl, modr;
 		struct symbol *b1, *b2;
 		// NULL pointer is always OK
 		int is_null = is_null_pointer_constant(*rp);
@@ -1471,7 +1472,10 @@ static int check_assignment_types(struct symbol *target, struct expression **rp,
 			goto Cast;
 		}
 		/* It's OK if the target is more volatile or const than the source */
-		*typediff = type_difference(&t->ctype, &s->ctype, 0, mod1);
+		/* It's OK if the source is more pure/noreturn than the target */
+		modr = mod1 & ~MOD_REV_QUAL;
+		modl = mod2 &  MOD_REV_QUAL;
+		*typediff = type_difference(&t->ctype, &s->ctype, modl, modr);
 		if (*typediff)
 			return 0;
 		return 1;
diff --git a/symbol.h b/symbol.h
index 516b6136..2465d6d8 100644
--- a/symbol.h
+++ b/symbol.h
@@ -253,6 +253,8 @@ struct symbol {
 #define MOD_TYPEOF	(MOD_QUALIFIER | MOD_NOCAST | MOD_SPECIFIER)
 /* modifiers for funtion attributes */
 #define MOD_FUN_ATTR	(MOD_PURE|MOD_NORETURN)
+/* like cvr-qualifiers but 'reversed' (OK: source <= target) */
+#define MOD_REV_QUAL	(MOD_PURE|MOD_NORETURN)
 
 
 /* Current parsing/evaluation function */