Add clang-format-12 source format placeholder

* Add duktape-clang-format Docker image with clang-format-12.

* Add Makefile target docker-image-clang-format to build the image,
  and clang-format-source to format src-input sources in-place.

* No CI integration or automation yet, .clang-format is also a
  placeholder.

.clang-format

@@ -0,0 +1,6 @@
+# https://clang.llvm.org/docs/ClangFormatStyleOptions.html
+
+BasedOnStyle: LLVM
+IndentWidth: 8
+TabWidth: 8
+ColumnLimit: 100

Makefile

@@ -1213,6 +1213,13 @@ codepolicycheck:
 codepolicycheckvim:
 	-$(PYTHON2) util/check_code_policy.py --dump-vim-commands src-input/*.c src-input/*.h src-input/*.h.in tests/api/*.c
 
+.PHONY: clang-format-source
+clang-format-source: | tmp
+	-rm -f tmp/docker-clang-format-input.zip tmp/docker-clang-format-output.zip
+	zip -1 -q -r tmp/docker-clang-format-input.zip .clang-format src-input
+	$(DOCKER) run --rm -i duktape-clang-format < tmp/docker-clang-format-input.zip > tmp/docker-clang-format-output.zip
+	unzip -q -o tmp/docker-clang-format-output.zip ; true  # avoid failure due to leading garbage
+
 # Simple heap graph and peak usage using valgrind --tool=massif, for quick
 # and dirty baseline comparison.  Say e.g. 'make massif-test-dev-hello-world'.
 # The target name is intentionally not 'massif-%.out' so that the rule is never
@@ -1275,11 +1282,16 @@ docker-images-s390x: docker-prepare
 	$(DOCKER) build -t duktape-shell-ubuntu-18.04-s390x docker/duktape-shell-ubuntu-18.04-s390x
 
 # Build Docker image for fuzzilli fuzz testing, tag as 'fuzzilli'.
+.PHONY: docker-image-fuzzilli
 docker-image-fuzzilli: build/duk-fuzzilli deps/fuzzilli
 	mkdir -p deps/fuzzilli/Cloud/Docker/DuktapeBuilder/out
 	cp build/duk-fuzzilli deps/fuzzilli/Cloud/Docker/DuktapeBuilder/out/
 	cd deps/fuzzilli/Cloud/Docker; ./build.sh fuzzilli # Don't use duktape build option here, as duk-fuzzilli is already present
 
+.PHONY: docker-image-clang-format
+docker-image-clang-format:
+	$(DOCKER) build --build-arg UID=$(shell id -u) --build-arg GID=$(shell id -g) -t duktape-clang-format docker/duktape-clang-format
+
 .PHONY: docker-images
 docker-images: docker-images-x64
 

docker/duktape-clang-format/Dockerfile

@@ -0,0 +1,33 @@
+# Docker image to run clang-format on input source files.
+
+FROM ubuntu:20.04
+
+# Username is assumed to be 'duktape' for now, change only UID/GID if required.
+ARG USERNAME=duktape
+ARG UID=1000
+ARG GID=1000
+
+RUN echo "=== Package installation ===" && \
+	apt-get update && apt-get install -qqy clang-format-12 zip unzip
+
+# Add non-root uid/gid to image, replicating host uid/gid if possible.
+RUN echo "=== User setup, /work directory creation ===" && \
+	groupadd -g $GID -o $USERNAME && \
+	useradd -m -u $UID -g $GID -o -s /bin/bash $USERNAME && \
+	mkdir /work && chown $UID:$GID /work && chmod 755 /work && \
+	echo "PS1='\033[40;37mDOCKER\033[0;34m \u@\h [\w] >>>\033[0m '" > /root/.profile && \
+	echo "PS1='\033[40;37mDOCKER\033[0;34m \u@\h [\w] >>>\033[0m '" > /home/$USERNAME/.profile && \
+	chown $UID:$GID /home/$USERNAME/.profile
+
+# Switch to non-root user.  (Note that COPY will still copy files as root,
+# so use COPY --chown for files copied.)
+USER $USERNAME
+
+# Use /work for builds, temporaries, etc.
+WORKDIR /work
+
+COPY --chown=duktape:duktape run.sh .
+RUN chmod 755 run.sh
+
+# ZIP in, ZIP out.
+ENTRYPOINT ["/work/run.sh"]

docker/duktape-clang-format/run.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -e
+
+cat >/tmp/stdin.zip
+mkdir reformat && cd reformat
+unzip -q /tmp/stdin.zip
+
+clang-format-12 -i `find src-input -type f | egrep '(.c|.h|.c.in|.c.in)'`
+
+zip -1 -q -r /tmp/stdout.zip *
+cat /tmp/stdout.zip