CI: Enforce UTF-8 for .cpp/.h/.txt files

.github/workflows/ci-misc.yml

@@ -0,0 +1,14 @@
+name: Misc checks
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  check-utf8-encoding:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: ./tools/check-utf8.sh

tools/check-utf8.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+invalid_found=0
+
+# We would like to redirect iconv output to /dev/null, but the macOS version of
+# iconv has problems with this ("iconv: iconv(): Inappropriate ioctl for
+# device", sporadically for particular inputs). So use a regular file instead.
+tmpfile=/tmp/check-utf8-temp
+trap "rm -f $tmpfile" EXIT
+
+for file in $(git ls-files | grep -E '\.(cpp|h|txt)$'); do
+    if ! iconv -f UTF-8 "$file" >$tmpfile; then
+        echo "Not valid UTF-8: $file" >&2
+        invalid_found=1
+    fi
+done
+
+[ $invalid_found = 0 ] && echo "All checked files are valid UTF-8" >&2
+
+exit $invalid_found