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] 3a1d4aa089
[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/
Pull-request: #842
Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: David Sterba <dsterba@suse.com>
61e7ade17e