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- From 0d2bf742df7f6b6d91fff8abe3c2f8b6ef0e0c01 Mon Sep 17 00:00:00 2001
- From: Julien Olivain <ju.o@free.fr>
- Date: Sun, 14 Jul 2024 12:52:33 +0200
- Subject: [PATCH] btrfs-progs: kerncompat: fix fallthrough definition for gcc
- 5.x and 6.x.
- Commit [1] 3a1d4aa089 "btrfs-progs: fix fallthrough cases with proper
- attributes" introduced a macro "fallthrough" to better handle compiler
- warnings of fallthrough situations.
- This macro is defined using the "__has_attribute" built-in
- function-like macro, which was introduced in GCC 5. See [2]. It then
- test for the "__fallthrough__" attribute, which was introduced in
- GCC 7. See [3].
- When compiling with a gcc version which supports "__has_attribute" and
- not the "__fallthrough__" attribute, compilation fails with error
- message:
- common/format-output.c: In function 'print_escaped':
- common/format-output.c:78:4: error: 'fallthrough' undeclared (first use in this function)
- fallthrough;
- ^
- btrfs-progs claim to support gcc at minimal version 4.8 in [4].
- This commit fixes this issue by adding the missing definition.
- The definition of the unsupported case is duplicated, because testing
- for "__has_attribute" and an attribute at the same time is not
- portable. See the cpp "__has_attribute" documentation [5].
- Note: the issue was found with Buildroot Linux [6], while testing with
- the command "utils/test-pkg -a -p btrfs-progs".
- [1] https://github.com/kdave/btrfs-progs/commit/3a1d4aa089419b7c94b31ff87122fa74907e1aa6
- [2] https://gcc.gnu.org/gcc-5/changes.html
- [3] https://gcc.gnu.org/gcc-7/changes.html
- [4] https://github.com/kdave/btrfs-progs/tree/v6.9.2#build-compatibility
- [5] https://gcc.gnu.org/onlinedocs/cpp/_005f_005fhas_005fattribute.html
- [6] https://buildroot.org/
- Upstream: Proposed: https://github.com/kdave/btrfs-progs/pull/842
- Signed-off-by: Julien Olivain <ju.o@free.fr>
- ---
- include/kerncompat.h | 2 ++
- 1 file changed, 2 insertions(+)
- diff --git a/include/kerncompat.h b/include/kerncompat.h
- index 31cd9d8d..bcd46bde 100644
- --- a/include/kerncompat.h
- +++ b/include/kerncompat.h
- @@ -305,6 +305,8 @@ static inline void up_read(struct rw_semaphore *sem)
- #if defined __has_attribute
- # if __has_attribute(__fallthrough__)
- # define fallthrough __attribute__((__fallthrough__))
- +# else
- +# define fallthrough do {} while (0) /* fallthrough */
- # endif
- #else
- # define fallthrough do {} while (0) /* fallthrough */
- --
- 2.45.2
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