Our __get_user_e() and __put_user_e() macros cause newer versions
of clang to generate false-positive -Waddress-of-packed-member
warnings if they are passed the address of a member of a packed
struct (see https://bugs.llvm.org/show_bug.cgi?id=39113).
Suppress these using the _Pragma() operator.
To put in the pragmas we need to convert the macros from
expressions to statements, but all the callsites effectively
treat them as statements already so this is OK.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
linux-user/qemu.h | 57 +++++++++++++++++++++++++++++++----------------
1 file changed, 38 insertions(+), 19 deletions(-)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index b4959e41c6e..56c4f2d5374 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -461,27 +461,46 @@ static inline int access_ok(int type, abi_ulong addr,
abi_ulong size)
These are usually used to access struct data members once the struct has
been locked - usually with lock_user_struct. */
-/* Tricky points:
- - Use __builtin_choose_expr to avoid type promotion from ?:,
- - Invalid sizes result in a compile time error stemming from
- the fact that abort has no parameters.
- - It's easier to use the endian-specific unaligned load/store
- functions than host-endian unaligned load/store plus tswapN. */
+/*
+ * Tricky points:
+ * - Use __builtin_choose_expr to avoid type promotion from ?:,
+ * - Invalid sizes result in a compile time error stemming from
+ * the fact that abort has no parameters.
+ * - It's easier to use the endian-specific unaligned load/store
+ * functions than host-endian unaligned load/store plus tswapN.
+ * - The pragmas are necessary only to silence a clang false-positive
+ * warning: see https://bugs.llvm.org/show_bug.cgi?id=39113 .
+ * - We have to disable -Wpragmas warnings to avoid a complaint about
+ * an unknown warning type from older compilers that don't know about
+ * -Waddress-of-packed-member.
+ */
+#define __put_user_e(x, hptr, e) \
+ do { \
+ _Pragma("GCC diagnostic push"); \
+ _Pragma("GCC diagnostic ignored \"-Wpragmas\""); \
+ _Pragma("GCC diagnostic ignored \"-Waddress-of-packed-member\""); \
+ (__builtin_choose_expr(sizeof(*(hptr)) == 1, stb_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 2, stw_##e##_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 4, stl_##e##_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 8, stq_##e##_p, abort)))) \
+ ((hptr), (x)), (void)0); \
+ _Pragma("GCC diagnostic pop"); \
+ } while (0)
-#define __put_user_e(x, hptr, e) \
- (__builtin_choose_expr(sizeof(*(hptr)) == 1, stb_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 2, stw_##e##_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 4, stl_##e##_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 8, stq_##e##_p, abort)))) \
- ((hptr), (x)), (void)0)
+#define __get_user_e(x, hptr, e) \
+ do { \
+ _Pragma("GCC diagnostic push"); \
+ _Pragma("GCC diagnostic ignored \"-Wpragmas\""); \
+ _Pragma("GCC diagnostic ignored \"-Waddress-of-packed-member\""); \
+ ((x) = (typeof(*hptr))( \
+ __builtin_choose_expr(sizeof(*(hptr)) == 1, ldub_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 2, lduw_##e##_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 4, ldl_##e##_p, \
+ __builtin_choose_expr(sizeof(*(hptr)) == 8, ldq_##e##_p, abort)))) \
+ (hptr)), (void)0); \
+ _Pragma("GCC diagnostic pop"); \
+ } while (0)
-#define __get_user_e(x, hptr, e) \
- ((x) = (typeof(*hptr))( \
- __builtin_choose_expr(sizeof(*(hptr)) == 1, ldub_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 2, lduw_##e##_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 4, ldl_##e##_p, \
- __builtin_choose_expr(sizeof(*(hptr)) == 8, ldq_##e##_p, abort)))) \
- (hptr)), (void)0)
#ifdef TARGET_WORDS_BIGENDIAN
# define __put_user(x, hptr) __put_user_e(x, hptr, be)
--
2.19.0
