Build the service in a container, and fix what the target compiler found

The openlgtv NDK is a Linux toolchain with no macOS or Windows build, so
tools/build.sh could not produce a binary anywhere else. docker-build.sh
bakes the SDK into an image and compiles there; packaging and deploy stay
on the host, where the TV is reachable. The SDK ships aarch64 as well as
x86_64, so the image picks the one matching the daemon and Apple Silicon
builds natively rather than under emulation.

Cross-compiling for real turned up three things the host compiler did
not:

  sink_hyperhdr_viz.c  read p->width and p->height to format the error
                       message after free(p)
  sink_hyperhdr.c      an SDP connection line of 128 bytes cannot hold
                       "IN IP4 " plus a 127-byte host plus "/255", so a
                       long hostname would silently lose its TTL suffix
  common/log.c         the log body was sized to the whole ring line,
                       leaving nothing for the prefix; budget for it so
                       the bound is provable rather than left to
                       snprintf

A clean cross-compile is now warning-free, and readelf confirms the
design rule holds: luna-service2, glib, PmLogLib and libc, with no
libpulse or libasound.

Also: @webosose/ares-cli was pinned to ^3.0.0, which does not exist
(latest is 2.4.0), so npm install failed outright. build.sh now puts
node_modules/.bin on PATH so a local install is enough.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -4,3 +4,4 @@ node_modules/
 __pycache__/
 *.pyc
 .DS_Store
+.vscode/

README.md

@@ -61,7 +61,16 @@ Channel's *Install from file*, or from a workstation:
 ares-install --device tv out/org.webosbrew.audiocap_1.0.0_all.ipk
 ```
 
-**From source.** See [docs/development.md](docs/development.md).
+**From source.** The NDK is Linux-only, so on macOS or Windows the compile goes
+through Docker:
+
+```sh
+npm install                                  # ares-cli
+./tools/docker-build.sh                      # or ./tools/build.sh native on Linux
+./tools/build.sh package                     # -> out/*.ipk
+```
+
+See [docs/development.md](docs/development.md) for the rest.
 
 ## First run
 

docs/development.md

@@ -4,17 +4,32 @@
 
 | For | Install |
 | --- | --- |
-| the native service | the [openlgtv buildroot NDK](https://github.com/openlgtv/buildroot-nc4/releases), `arm-webos-linux-gnueabi_sdk-buildroot` |
-| packaging | `npm install -g @webosose/ares-cli` |
+| the native service | the [openlgtv buildroot NDK](https://github.com/openlgtv/buildroot-nc4/releases) — or Docker, see below |
+| packaging | `npm install` (ares-cli), or `npm install -g @webosose/ares-cli` |
 | the tests | a host C compiler, Python 3, Node (optional: `flatbuffers`, `jsdom`) |
 
-Unpack the NDK and relocate it once:
+### The toolchain
+
+The NDK is a **Linux** toolchain — there is no macOS or Windows build of it. On
+Linux, unpack and relocate it once:
 
 ```sh
-tar xf arm-webos-linux-gnueabi_sdk-buildroot.tar.gz -C "$HOME"
+tar xf arm-webos-linux-gnueabi_sdk-buildroot-x86_64.tar.gz -C "$HOME"
 "$HOME/arm-webos-linux-gnueabi_sdk-buildroot/relocate-sdk.sh"
 ```
 
+Everywhere else, build the native part in a container:
+
+```sh
+./tools/docker-build.sh     # -> build/native/audiocap-service
+```
+
+That bakes the SDK into an image, so it downloads once and later builds start
+immediately. There are aarch64 and x86_64 SDK builds and the image picks
+whichever matches the container, so on Apple Silicon it runs natively rather
+than under emulation. Only the compile happens in the container; packaging and
+deployment run on the host, where the TV is reachable.
+
 Register the TV with ares once, using the Homebrew Channel's ssh (port 9922,
 root):
 
@@ -32,11 +47,19 @@ ares-setup-device --add tv \
 ./tools/build.sh logs
 ```
 
+With the container toolchain it is two steps, since `build.sh` only knows how
+to drive a local NDK:
+
+```sh
+./tools/docker-build.sh && ./tools/build.sh package
+```
+
 `DEVICE=livingroom ./tools/build.sh install` targets a different device;
 `WEBOS_SDK=/opt/webos-sdk ./tools/build.sh` a differently placed NDK.
 
 The same commands exist as npm scripts (`npm run build`, `npm run deploy`, …)
-if that is more your habit.
+if that is more your habit. `build.sh` puts `node_modules/.bin` on PATH first,
+so a local `npm install` of ares-cli is enough — no global install needed.
 
 ### What the packaging step does
 
@@ -92,7 +115,7 @@ npm run serve      # http://localhost:8000
 
    ```sh
    python3 tools/make-manifest.py \
-     --base-url https://github.com/you/lgtv-audio-cap/releases/download/v1.0.0
+     --base-url https://git.crylia.de/Crylia/lgtv_audio_cap/releases/download/v1.0.0
    ```
 
 5. Submit the manifest URL to [webosbrew/repo](https://github.com/webosbrew/repo).

native/src/common/log.c

@@ -9,6 +9,8 @@
 
 #define RING_LINES 200
 #define RING_LINE_LEN 256
+// "HH:MM:SS.mmm [level] file.c:1234 " — 64 covers it with room to spare.
+#define RING_LINE_PREFIX 64
 
 static log_level_t s_level = LOG_INFO;
 static pthread_mutex_t s_lock = PTHREAD_MUTEX_INITIALIZER;
@@ -56,7 +58,10 @@ void log_printf(log_level_t level, const char* file, int line, const char* fmt,
     snprintf(stamp, sizeof(stamp), "%02d:%02d:%02d.%03d", tm.tm_hour, tm.tm_min,
         tm.tm_sec, (int)(tv.tv_usec / 1000));
 
-    char body[RING_LINE_LEN];
+    // A ring line is a fixed size, so an over-long message is truncated rather
+    // than allowed to grow the buffer. Budgeting for the prefix here keeps the
+    // final snprintf provably within bounds instead of relying on it to clip.
+    char body[RING_LINE_LEN - RING_LINE_PREFIX];
     va_list ap;
     va_start(ap, fmt);
     vsnprintf(body, sizeof(body), fmt, ap);

native/src/sinks/sink_hyperhdr.c

@@ -79,7 +79,9 @@ static int build_sdp(hh_priv_t* p, char* out, size_t cap)
     char src_str[INET_ADDRSTRLEN];
     snprintf(src_str, sizeof(src_str), "%s", inet_ntoa(src));
 
-    char conn[128];
+    // Wide enough for the longest host plus the prefix and the TTL suffix, so
+    // a long hostname cannot quietly lose its "/255" to truncation.
+    char conn[sizeof(p->host) + 16];
     if (p->multicast) {
         // The /255 suffix is the TTL, required for multicast connection lines.
         snprintf(conn, sizeof(conn), "IN IP4 %s/255", p->host);

native/src/sinks/sink_hyperhdr_viz.c

@@ -388,9 +388,9 @@ static sink_t* viz_open(const json_value_t* cfg, const audio_format_t* fmt, char
     p->frame_bytes = (size_t)p->width * (size_t)p->height * 3;
     p->frame = calloc(1, p->frame_bytes);
     if (!p->frame) {
+        snprintf(err, errlen, "out of memory allocating %dx%d frame", p->width, p->height);
         free(p);
         free(s);
-        snprintf(err, errlen, "out of memory allocating %dx%d frame", p->width, p->height);
         return NULL;
     }
 

package.json

@@ -2,12 +2,20 @@
   "name": "lgtv-audio-cap",
   "version": "1.0.0",
   "private": true,
-  "description": "Captures audio on an LG webOS 5/6 TV and streams it out — HyperHDR first, plus raw UDP, TCP and HTTP.",
-  "keywords": ["webos", "lgtv", "hyperhdr", "hyperion", "audio", "webosbrew"],
+  "description": "Captures audio on an LG webOS 5/6 TV and streams it out \u2014 HyperHDR first, plus raw UDP, TCP and HTTP.",
+  "keywords": [
+    "webos",
+    "lgtv",
+    "hyperhdr",
+    "hyperion",
+    "audio",
+    "webosbrew"
+  ],
   "license": "MIT",
   "scripts": {
     "build": "tools/build.sh",
     "native": "tools/build.sh native",
+    "docker": "tools/docker-build.sh",
     "stage": "tools/build.sh stage",
     "package": "tools/build.sh package",
     "deploy": "tools/build.sh install && tools/build.sh launch",
@@ -21,7 +29,7 @@
     "serve": "python3 -m http.server 8000 --directory frontend"
   },
   "devDependencies": {
-    "@webosose/ares-cli": "^3.0.0",
+    "@webosose/ares-cli": "^2.4.0",
     "jsdom": "^24.0.0"
   }
 }

tools/build.sh

@@ -17,6 +17,10 @@ set -euo pipefail
 ROOT="$(cd "$(dirname "$0")/.." && pwd)"
 cd "$ROOT"
 
+# `npm install` puts ares-cli here rather than on PATH, so a local install works
+# without also needing the global one.
+[ -d "$ROOT/node_modules/.bin" ] && PATH="$ROOT/node_modules/.bin:$PATH"
+
 APP_ID=org.webosbrew.audiocap
 SERVICE_ID=$APP_ID.service
 BINARY=audiocap-service
@@ -52,6 +56,11 @@ Download and unpack the buildroot NDK, then point WEBOS_SDK at it:
   \$HOME/arm-webos-linux-gnueabi_sdk-buildroot/relocate-sdk.sh
 
   WEBOS_SDK=\$HOME/arm-webos-linux-gnueabi_sdk-buildroot ./tools/build.sh
+
+The SDK only runs on Linux. On macOS or Windows, compile in a container
+instead and then come back here to package:
+
+  ./tools/docker-build.sh && ./tools/build.sh package
 EOF
     exit 1
   fi

tools/docker-build.sh

@@ -0,0 +1,109 @@
+#!/usr/bin/env bash
+# Cross-compiles the service inside a container, for hosts that cannot run the
+# NDK directly. The openlgtv buildroot SDK is a Linux toolchain, so on macOS or
+# Windows this is the only way to build the native part.
+#
+#   ./tools/docker-build.sh          # build the service into build/native/
+#   ./tools/docker-build.sh shell    # a prompt inside the SDK, for poking about
+#   ./tools/docker-build.sh clean    # drop the image
+#
+# The SDK is baked into an image, so it is downloaded once (~350 MB) and every
+# build after the first starts instantly. There are aarch64 and x86_64 builds
+# of the SDK and the image picks the one matching the container, so this runs
+# natively on Apple Silicon rather than under emulation.
+#
+# NDK_RELEASE pins the SDK release; DOCKER is podman if you prefer.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$ROOT"
+
+DOCKER="${DOCKER:-docker}"
+NDK_RELEASE="${NDK_RELEASE:-webos-a38c582}"
+IMAGE="${IMAGE:-lgtv-audiocap-sdk:$NDK_RELEASE}"
+SDK=/opt/webos-sdk
+TOOLCHAIN="$SDK/share/buildroot/toolchainfile.cmake"
+BUILD_DIR=build/native
+
+say() { printf '%s\n' "$*"; }
+step() { printf '\n== %s\n' "$*"; }
+die() { printf 'error: %s\n' "$*" >&2; exit 1; }
+
+command -v "$DOCKER" >/dev/null 2>&1 || die "$DOCKER is not installed"
+
+build_image() {
+  if "$DOCKER" image inspect "$IMAGE" >/dev/null 2>&1; then
+    return
+  fi
+  step "Building the SDK image (once, ~350 MB download)"
+  # The arch is resolved inside the build so the image is right for whatever
+  # the daemon runs, without the caller having to know.
+  "$DOCKER" build --tag "$IMAGE" - <<EOF
+FROM debian:bookworm-slim
+RUN apt-get update \\
+ && apt-get install -y --no-install-recommends \\
+      ca-certificates curl cmake make file python3 \\
+ && rm -rf /var/lib/apt/lists/*
+RUN case "\$(uname -m)" in \\
+      aarch64|arm64) arch=aarch64 ;; \\
+      x86_64|amd64)  arch=x86_64 ;; \\
+      *) echo "no webOS SDK for \$(uname -m)" >&2; exit 1 ;; \\
+    esac \\
+ && mkdir -p $SDK \\
+ && curl -fL "https://github.com/openlgtv/buildroot-nc4/releases/download/$NDK_RELEASE/arm-webos-linux-gnueabi_sdk-buildroot-\$arch.tar.gz" \\
+    | tar xz -C $SDK --strip-components=1 \\
+ && $SDK/relocate-sdk.sh
+EOF
+}
+
+# --user keeps build/ owned by the caller instead of root. HOME has to point
+# somewhere writable or cmake complains about its package registry.
+run() {
+  "$DOCKER" run --rm \
+    --volume "$ROOT:/src" \
+    --workdir /src \
+    --user "$(id -u):$(id -g)" \
+    --env HOME=/tmp \
+    "$@"
+}
+
+compile() {
+  build_image
+
+  # A cache from a differently placed toolchain cannot be reused.
+  if [ -f "$BUILD_DIR/CMakeCache.txt" ] \
+     && ! grep -q "CMAKE_TOOLCHAIN_FILE:.*=$TOOLCHAIN" "$BUILD_DIR/CMakeCache.txt"; then
+    say "discarding a cmake cache from a different toolchain"
+    rm -rf "$BUILD_DIR"
+  fi
+
+  step "Cross-compiling the service"
+  run --interactive=false "$IMAGE" sh -c "
+    set -e
+    cmake -S native -B $BUILD_DIR \
+      -DCMAKE_TOOLCHAIN_FILE=$TOOLCHAIN \
+      -DCMAKE_BUILD_TYPE=Release
+    cmake --build $BUILD_DIR --parallel
+    file $BUILD_DIR/audiocap-service
+  "
+
+  [ -f "$BUILD_DIR/audiocap-service" ] || die "the build produced no binary"
+  say ""
+  say "built $BUILD_DIR/audiocap-service"
+  say "now: ./tools/build.sh package"
+}
+
+case "${1:-build}" in
+  build) compile ;;
+  shell)
+    build_image
+    step "A shell in the SDK image; the toolchain is at $SDK"
+    run --interactive --tty "$IMAGE" bash
+    ;;
+  clean)
+    "$DOCKER" image rm "$IMAGE" 2>/dev/null && say "removed $IMAGE" || say "no image to remove"
+    ;;
+  -h|--help)
+    awk 'NR == 1 { next } /^#/ { sub(/^# ?/, ""); print; next } { exit }' "$0" ;;
+  *) die "unknown command '$1' (try --help)" ;;
+esac

tools/make-manifest.py

@@ -22,7 +22,7 @@ import sys
 HERE = os.path.dirname(os.path.abspath(__file__))
 ROOT = os.path.join(HERE, os.pardir)
 
-SOURCE_URL = "https://github.com/webosbrew/lgtv-audio-cap"
+SOURCE_URL = "https://git.crylia.de/Crylia/lgtv_audio_cap"
 
 
 def newest_ipk(directory):