ci: Add static build job

This commit adds a simple CI job that just tests if bpftrace can build
statically. No additional tests are run -- in the past we have not seen
much benefit in embedded-build tests. It was, however, a massive
headache to maintain. So this time we only build.

Nix was not chosen to do static builds as the `pkgsStatic` ecosystem has
some pretty annoying bugs. Basically pkgsStatic applies overlays to try
and statically build all the packages it typically dynamically links
for. While clever, there are bugs everywhere. So it wasn't worth the
hassle. Alpine linux + docker seemed like a much easier option to
maintain.

.github/include/static.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+#
+# This script is the entrypoint for the static build.
+#
+# To make CI errors easier to reproduce locally, please limit
+# this script to using only git, docker, and coreutils.
+
+set -eux
+
+IMAGE=bpftrace-static
+cd $(git rev-parse --show-toplevel)
+
+# Build the base image
+docker build -t "$IMAGE" -f docker/Dockerfile.static docker/
+
+# Perform bpftrace static build
+docker run -v $(pwd):$(pwd) -w $(pwd) -i "$IMAGE" <<'EOF'
+set -eux
+BUILD_DIR=build-static
+cmake -B "$BUILD_DIR" -DCMAKE_BUILD_TYPE=Release -DCMAKE_VERBOSE_MAKEFILE=ON -DBUILD_TESTING=OFF -DSTATIC_LINKING=ON
+make -C "$BUILD_DIR" -j$(nproc)
+
+# Basic smoke test
+./"$BUILD_DIR"/src/bpftrace --help
+
+# Validate that it's a mostly static binary except for libc
+EXPECTED="/lib/ld-musl-x86_64.so.1\nlibc.musl-x86_64.so.1"
+GOT=$(ldd "$BUILD_DIR"/src/bpftrace | awk '{print $1}')
+if ! diff <(echo -e "$EXPECTED") <(echo "$GOT"); then
+ set +x
+ >&2 echo "bpftrace incorrectly linked"
+ exit 1
+fi
+EOF

.github/workflows/static.yml

@@ -0,0 +1,16 @@
+name: Static
+
+on: [push, pull_request]
+
+# Cancel previous run if a new one is started
+concurrency:
+ group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+ cancel-in-progress: true
+
+jobs:
+ build:
+ runs-on: ubuntu-latest
+ steps:
+ - uses: actions/checkout@v2
+ - name: Build static bpftrace
+ run: ./.github/include/static.sh

docker/Dockerfile.static

@@ -0,0 +1,44 @@
+# This Dockerfile is used to test STATIC_LINKING=ON builds in the CI
+
+FROM alpine:3.18
+
+RUN apk add --update \
+ asciidoctor \
+ argp-standalone \
+ bash \
+ bcc-dev \
+ bcc-static \
+ bison \
+ bzip2-static \
+ build-base \
+ cereal \
+ clang-dev \
+ clang-static \
+ cmake \
+ elfutils-dev \
+ flex-dev \
+ git \
+ gtest-dev \
+ libbpf-dev \
+ libelf-static \
+ libpcap-dev \
+ libc6-compat \
+ linux-headers \
+ llvm16-dev \
+ llvm16-static \
+ musl-obstack-dev \
+ openssl-dev \
+ pahole \
+ procps \
+ python3 \
+ wget \
+ xxd \
+ xz-static \
+ zlib-dev \
+ zlib-static \
+ zstd-dev \
+ zstd-static
+
+# It looks like llvm16 prefers to dynamically link against zstd. Extremely
+# unclear why. Work around it by modifying LLVMExports.cmake.
+RUN sed -i 's/libzstd_shared/libzstd_static/g' /usr/lib/llvm16/lib/cmake/llvm/LLVMExports.cmake