[PATCH 1/1] perf build x86: Fix SC2034 error in syscalltbl.sh

[PATCH 1/1] perf build x86: Fix SC2034 error in syscalltbl.sh

[Haoze Xie]

Change the unused var in 'arch/x86/entry/syscalls/syscalltbl.sh' to '_'
when reading from '$sorted_table'. This change allows the script to pass
tests of ShellCheck before and after version 0.7.2 at the same time.

When building in arch x86, syscalltbl.sh got a ShellCheck warning, which
makes compilation error:

    In arch/x86/entry/syscalls/syscalltbl.sh line 27:
    while read nr _abi name entry _compat; do
                  ^-^ SC2034: abi appears unused.
                  Verify use (or export if used externally).
                                  ^----^ SC2034: compat appears unused.
                               Verify use (or export if used externally).

The script reads unused param abi and compat. It uses format '_xxx' to
indicate dummy vars, which won't work properly when ShellCheck <= 0.7.2.

According to SC2034, the more general way of writing is to use directly
'_' to indicate discarding vars. 'entry' is also replaced by '_' because
it just happens to be defined in emit function, otherwise it will lead
to some misunderstandings.

Link: https://www.shellcheck.net/wiki/SC2034
Signed-off-by: Haoze Xie <royenheart@gmail.com>
Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
---
 tools/perf/arch/x86/entry/syscalls/syscalltbl.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/arch/x86/entry/syscalls/syscalltbl.sh b/tools/perf/arch/x86/entry/syscalls/syscalltbl.sh
index 59d7914ed6bb..2b71f99933a5 100755
--- a/tools/perf/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/tools/perf/arch/x86/entry/syscalls/syscalltbl.sh
@@ -24,7 +24,9 @@ sorted_table=$(mktemp /tmp/syscalltbl.XXXXXX)
 grep '^[0-9]' "$in" | sort -n > $sorted_table
 
 max_nr=0
-while read nr _abi name entry _compat; do
+# the params are: nr abi name entry compat
+# use _ for intentionally unused variables according to SC2034
+while read nr _ name _ _; do
     if [ $nr -ge 512 ] ; then # discard compat sycalls
         break
     fi
-- 
2.25.1

Re: [PATCH 1/1] perf build x86: Fix SC2034 error in syscalltbl.sh

[Namhyung Kim]

On Mon, 08 Jul 2024 02:04:02 +0800, Haoze Xie wrote:

> Change the unused var in 'arch/x86/entry/syscalls/syscalltbl.sh' to '_'
> when reading from '$sorted_table'. This change allows the script to pass
> tests of ShellCheck before and after version 0.7.2 at the same time.
> 
> When building in arch x86, syscalltbl.sh got a ShellCheck warning, which
> makes compilation error:
> 
> [...]

Applied to perf-tools-next, thanks!

Best regards,
Namhyung