scripts/check-local-export: avoid 'wait $!' for process substitution
PATCH 1/1 scripts/check-local-export: avoid 'wait $!' for process substitution
Bash>=4.4 supports 'wait $!' to check the exit status of a process substitution, but some people using older bash versions reported an error like this:
./scripts/check-local-export: line 54: wait: pid 17328 is not a child of this shell
I used the process substitution because a pipeline executes each command in a subshell; variables modified within the while-loop in the subshell context would be lost after the subshell terminates.
Fortunately, Bash>=4.2 supports the 'lastpipe' option, which runs the last element of a pipeline in the current shell process.
Also, set 'pipefail' to catch errors from ${NM}.
Bash 4.2, released in 2011, is 5 years older than Bash 4.4.
Reported-by Tetsuo Handa <[email protected]>
Reported-by Michael Ellerman <[email protected]>
Reported-by Wang Yugui <[email protected]>
Signed-off-by Masahiro Yamada <[email protected]>
---
scripts/check-local-export | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-)
scripts/check-local-export +20 -15
@@ -8,11 +8,30 @@ set -e +# catch errors from ${NM} +set -o pipefail + +# Run the last element of a pipeline in the current shell. +# Without this, the while-loop would be executed in a subshell, and +# the changes made to 'symbol_types' and 'export_symbols' would be lost. +shopt -s lastpipe + declare -A symbol_types declare -a export_symbols exit_code=0 +# If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) shows +# 'no symbols' diagnostic (but exits with 0). It is harmless and hidden by +# '2>/dev/null'. However, it suppresses real error messages as well. Add a +# hand-crafted error message here. +# +# Use --quiet instead of 2>/dev/null when we upgrade the minimum version of +# binutils to 2.37, llvm to 13.0.0. +# +# Then, the following line will be really simple: +# ${NM} --quiet ${1} | +{ ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } } | while read value type name do # Skip the line if the number of fields is less than 3.
@@ -37,21 +56,7 @@ do if [[ ${name} == __ksymtab_* ]]; then export_symbols+=(${name#__ksymtab_}) fi - - # If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) - # shows 'no symbols' diagnostic (but exits with 0). It is harmless and - # hidden by '2>/dev/null'. However, it suppresses real error messages - # as well. Add a hand-crafted error message here. - # - # Use --quiet instead of 2>/dev/null when we upgrade the minimum version - # of binutils to 2.37, llvm to 13.0.0. - # - # Then, the following line will be really simple: - # done < <(${NM} --quiet ${1}) -done < <(${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } ) - -# Catch error in the process substitution -wait $! +done for name in "${export_symbols[@]}" do
Signature · 1 line
2.32.0