Clarify the preferable version for clang-format (#182)

The Ubuntu Linux 24.04 LTS release now includes Clang-format version 18
in its package management system. It is time to implement mandatory CI
pipeline checks and routine code formatting verification.

Author: jserv

.ci/check-format.sh

@@ -6,7 +6,7 @@ set -x
 
 for file in ${SOURCES};
 do
-    clang-format-16 ${file} > expected-format
+    clang-format-18 ${file} > expected-format
     diff -u -p --label="${file}" --label="expected coding style" ${file} expected-format
 done
-exit $(clang-format-16 --output-replacements-xml ${SOURCES} | grep -E -c "</replacement>")
+exit $(clang-format-18 --output-replacements-xml ${SOURCES} | grep -E -c "</replacement>")

.github/workflows/main.yml

@@ -36,7 +36,7 @@ jobs:
     - uses: actions/checkout@v4
     - name: coding convention
       run: |
-            sudo apt-get install -q -y clang-format-16
+            sudo apt-get install -q -y clang-format-18
             .ci/check-newline.sh
             .ci/check-format.sh
       shell: bash

CONTRIBUTING.md

@@ -44,7 +44,7 @@ However, participation requires adherence to fundamental ground rules:
   This variant should be considered the standard for all documentation efforts.
   For instance, opt for "initialize" over "initialise" and "color" rather than "colour".
 
-Software requirement: [clang-format](https://clang.llvm.org/docs/ClangFormat.html) version 12 or later.
+Software requirement: [clang-format](https://clang.llvm.org/docs/ClangFormat.html) version 18 or later.
 
 This repository consistently contains an up-to-date `.clang-format` file with rules that match the explained ones.
 For maintaining a uniform coding style, execute the command `clang-format -i *.[ch]`.

list.h

@@ -54,7 +54,7 @@ struct list_head {
     })
 #else
 #define container_of(ptr, type, member) \
-    ((type *) ((char *) (ptr) -offsetof(type, member)))
+    ((type *) ((char *) (ptr) - offsetof(type, member)))
 #endif
 #endif
 

scripts/checksums

@@ -1,2 +1,2 @@
 db6784ff3917888db4d1dceaa0570d99ed40e762  queue.h
-3337dbccc33eceedda78e36cc118d5a374838ec7  list.h
+bfb6df45d64356868c86a7173455d39970bd0270  list.h