Messages in this thread Patch in this message | | | From | Masahiro Yamada <> | Subject | [PATCH v3 1/3] compiler_types.h: make __builtin_types_compatible_p() noop for Sparse | Date | Mon, 19 Nov 2018 19:31:41 +0900 |
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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.masahiro@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
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