ci: re-add CodeQL workflow (public repo, hosted runner)

.github/workflows/codeql.yml

@@ -0,0 +1,109 @@
+name: CodeQL
+
+# Standalone CodeQL workflow (split out of build-test.yml so security analysis
+# evolves independently of the build/test pipeline and shows as its own
+# PR check). Third-party actions pinned to commit SHAs — see build-test.yml header.
+
+# nginx version is resolved at run time (see "Resolve latest mainline nginx"
+# step) rather than pinned, so this analysis tracks current mainline.
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+  NGINX_VERSION: ""
+
+on:
+  push:
+    branches: [master, main, dev]
+  pull_request:
+    branches: [master, main]
+  schedule:
+    # Monthly, day 1 @ 04:47 UTC (staggered per repo like ci-deep).
+    - cron: "47 4 1 * *"
+  workflow_dispatch: {}
+
+concurrency:
+  group: codeql-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  codeql:
+    name: CodeQL
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      contents: read
+      security-events: write
+
+    steps:
+      - name: Checkout module
+        uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+
+      - name: Resolve latest mainline nginx
+        run: |
+          set -euo pipefail
+          ver=$(curl -fsSL https://nginx.org/en/download.html \
+            | grep -oP 'nginx-\K[0-9]+\.[0-9]+\.[0-9]+(?=\.tar\.gz)' \
+            | sort -V | tail -1)
+          if [ -z "$ver" ]; then
+            echo "::error::could not resolve mainline nginx version from nginx.org"
+            exit 1
+          fi
+          echo "Resolved nginx mainline: $ver"
+          echo "NGINX_VERSION=$ver" >> "$GITHUB_ENV"
+
+      - name: Install build dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential pkg-config libzstd-dev \
+            libpcre2-dev zlib1g-dev wget
+
+      - name: Cache nginx source tarball
+        id: nginx-tarball
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
+        with:
+          path: nginx-${{ env.NGINX_VERSION }}.tar.gz
+          key: nginx-src-${{ env.NGINX_VERSION }}
+
+      - name: Download nginx source tarball
+        if: steps.nginx-tarball.outputs.cache-hit != 'true'
+        run: wget -q "https://nginx.org/download/nginx-${NGINX_VERSION}.tar.gz"
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4
+        with:
+          languages: c-cpp
+          queries: security-extended
+          paths: |
+            filter
+            static
+            *.c
+            *.h
+          paths-ignore: |
+            nginx-*
+
+      - name: Build module sources for CodeQL
+        run: |
+          tar -xzf "nginx-${NGINX_VERSION}.tar.gz"
+          cd "nginx-${NGINX_VERSION}"
+          # --add-module (static) compiles the zstd module objects INTO the
+          # nginx binary, so a full `make` is what the CodeQL tracer sees.
+          # `make modules` only builds --add-dynamic-module .so targets and
+          # leaves the static add-module untouched, which is why CodeQL
+          # reported "no source code seen during build". Do not redirect
+          # configure to /dev/null — a silent configure failure would also
+          # produce an empty CodeQL database.
+          ./configure \
+            --with-compat \
+            --with-debug \
+            --with-cc-opt="-DZSTD_STATIC_LINKING_ONLY $(pkg-config --cflags libzstd zlib libpcre2-8)" \
+            --with-ld-opt="$(pkg-config --libs libzstd zlib libpcre2-8)" \
+            --add-module="$GITHUB_WORKSPACE"
+          make -j"$(nproc)"
+
+      - name: Perform CodeQL analysis
+        uses: github/codeql-action/analyze@8aad20d150bbac5944a9f9d289da16a4b0d87c1e # v4
+        with:
+          category: "/language:c-cpp"

README.md

@@ -3,6 +3,7 @@
 [![Fuzzing](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/fuzzing.yml/badge.svg)](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/fuzzing.yml)
 [![Valgrind](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/valgrind.yml/badge.svg)](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/valgrind.yml)
 [![CI Deep](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/ci-deep.yml/badge.svg)](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/ci-deep.yml)
+[![CodeQL](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/codeql.yml/badge.svg)](https://github.com/myguard-labs/nginx-zstd-module/actions/workflows/codeql.yml)
 
 📖 **Background reading:** 
 - [zstd nginx module: what it does, bugs fixed](https://deb.myguard.nl/2026/05/zstd-nginx-module-what-it-does-bugs-fixed/)