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 <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Reported-by: Wang Yugui <wangyugui@xxxxxxxxxxxx>
Tested-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Tested-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---
Changes in v2:
- Add bash to Documentation/process/changes.rst
Documentation/process/changes.rst | 12 +++++++++++
scripts/check-local-export | 35 ++++++++++++++++++-------------
2 files changed, 32 insertions(+), 15 deletions(-)
diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 34415ae1af1b..19c286c23786 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -32,6 +32,7 @@ you probably needn't concern yourself with pcmciautils.
GNU C 5.1 gcc --version
Clang/LLVM (optional) 11.0.0 clang --version
GNU make 3.81 make --version
+bash 4.2 bash --version
binutils 2.23 ld -v
flex 2.5.35 flex --version
bison 2.0 bison --version
@@ -84,6 +85,12 @@ Make
You will need GNU make 3.81 or later to build the kernel.
+Bash
+----
+
+Some bash scripts are used for the kernel build.
+Bash 4.2 or newer is needed.
+
Binutils
--------
@@ -362,6 +369,11 @@ Make
- <ftp://ftp.gnu.org/gnu/make/>
+Bash
+----
+
+- <ftp://ftp.gnu.org/gnu/bash/>
+
Binutils
--------
diff --git a/scripts/check-local-export b/scripts/check-local-export
index da745e2743b7..e21c7b54885d 100755
--- a/scripts/check-local-export
+++ b/scripts/check-local-export
@@ -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
--
2.32.0
