Fix qualifiers on const array struct members

Use the existing array-aware qualifier helper when propagating qualifiers from a const or volatile aggregate to a selected field. This keeps address-of array members from spuriously warning while preserving warnings for discarded qualifiers and read-only writes.

Add regression coverage for pointer-to-array returns, array decay, and writes through const array members.

tccgen.c

@@ -6184,7 +6184,8 @@ special_math_val:
             gen_op('+');
             /* change type to field type, and set to lvalue */
             vtop->type = s->type;
-            vtop->type.t |= qualifiers;
+            if (qualifiers)
+                parse_btype_qualify(&vtop->type, qualifiers);
             /* an array is never an lvalue */
             if (!(vtop->type.t & VT_ARRAY)) {
                 vtop->r |= VT_LVAL;

tests/tests2/60_errors_and_warnings.c

@@ -551,4 +551,114 @@ int main(int argc, char **argv)
 
 }
 
+#elif defined test_const_array_member_addr_ok
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int_array const *get_array(const my_struct *s)
+{
+    return &(s->arr);
+}
+
+#elif defined test_const_array_member_decay_ok
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+const int *good_decay(const my_struct *s)
+{
+    return s->arr;
+}
+
+#elif defined test_const_array_member_addr_bad
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int_array *bad_array_addr(const my_struct *s)
+{
+    return &(s->arr);
+}
+
+#elif defined test_const_array_member_decay_bad
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int *bad_decay(const my_struct *s)
+{
+    return s->arr;
+}
+
+#elif defined test_const_array_member_write_bad
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+void bad_write(const my_struct *s)
+{
+    s->arr[0] = 1;
+}
+
+#elif defined test_const_struct_array_member_write_bad
+
+typedef struct { int x; } inner;
+typedef struct { inner arr[1]; } outer;
+
+void bad_inner_write(const outer *s)
+{
+    s->arr[0].x = 1;
+}
+
+#elif defined test_volatile_array_member_addr_ok
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int_array volatile *get_volatile_array(volatile my_struct *s)
+{
+    return &(s->arr);
+}
+
+#elif defined test_volatile_array_member_decay_ok
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+volatile int *good_volatile_decay(volatile my_struct *s)
+{
+    return s->arr;
+}
+
+#elif defined test_volatile_array_member_addr_bad
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int_array *bad_volatile_array_addr(volatile my_struct *s)
+{
+    return &(s->arr);
+}
+
+#elif defined test_volatile_array_member_decay_bad
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+int *bad_volatile_decay(volatile my_struct *s)
+{
+    return s->arr;
+}
+
+#elif defined test_volatile_array_member_write_ok
+
+typedef int int_array[1];
+typedef struct { int_array arr; } my_struct;
+
+void good_volatile_write(volatile my_struct *s)
+{
+    s->arr[0] = 1;
+}
+
 #endif

tests/tests2/60_errors_and_warnings.expect

@@ -262,3 +262,31 @@ bar 15 12 34
 [test_scope_3]
 60_errors_and_warnings.c:548: warning: assignment from incompatible pointer type
 60_errors_and_warnings.c:549: error: initialization of incomplete type
+
+[test_const_array_member_addr_ok]
+
+[test_const_array_member_decay_ok]
+
+[test_const_array_member_addr_bad]
+60_errors_and_warnings.c:581: warning: assignment discards qualifiers from pointer target type
+
+[test_const_array_member_decay_bad]
+60_errors_and_warnings.c:591: warning: assignment discards qualifiers from pointer target type
+
+[test_const_array_member_write_bad]
+60_errors_and_warnings.c:601: warning: assignment of read-only location
+
+[test_const_struct_array_member_write_bad]
+60_errors_and_warnings.c:611: warning: assignment of read-only location
+
+[test_volatile_array_member_addr_ok]
+
+[test_volatile_array_member_decay_ok]
+
+[test_volatile_array_member_addr_bad]
+60_errors_and_warnings.c:641: warning: assignment discards qualifiers from pointer target type
+
+[test_volatile_array_member_decay_bad]
+60_errors_and_warnings.c:651: warning: assignment discards qualifiers from pointer target type
+
+[test_volatile_array_member_write_ok]