When I tried to delete BUILD_BUG_ON stubs for sparse, the kbuild test
robot reported lots of Sparse warnings from container_of(), which
seem false positive.
The following checker in container_of() seems to be causing something
strange for Sparse.
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
!__same_type(*(ptr), void), \
"pointer type mismatch in container_of()"); \
I narrowed down the problem into the following test code:
--------------------(test_code.c begin)--------------------
struct foo {
int (*callback)(void);
};
void assert(int);
static inline struct foo *get_foo(void)
{
assert(__builtin_types_compatible_p(void, void));
return (struct foo *)0;
}
int test(void);
int test(void)
{
return get_foo()->callback();
}
---------------------(test_code.c end)---------------------
Of course, GCC (and Clang as well) can compile it:
$ gcc -Wall -c -o test_code.o test_code.c
However, Sparse complains about this obviously correct code:
$ sparse test_code.c
test_code.c:9:45: warning: unknown expression (4 0)
test_code.c:9:51: warning: unknown expression (4 0)
Interstingly, just removing the 'inline' keyword in the test code
makes Sparse happy.
I concluded that Sparse cannot handle __builtin_types_compatible_p()
correctly. Make it no-op.
Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
---
Changes in v3:
- New patch
Changes in v2: None
include/linux/compiler_types.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 4a3f9c0..9e7da0b 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -23,6 +23,7 @@
extern void __chk_user_ptr(const volatile void __user *);
extern void __chk_io_ptr(const volatile void __iomem *);
# define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *)
&(p)->member))
+# define __builtin_types_compatible_p(t1, t2) (1)
#else /* __CHECKER__ */
# ifdef STRUCTLEAK_PLUGIN
# define __user __attribute__((user))
--
2.7.4
