fix(alpine): build R with cairo, png, jpeg and tiff graphics devices (#9)

## Motivation

R on the Alpine images was built without graphics support: `capabilities()` reports `cairo`, `png`, `jpeg` and `tiff` as `FALSE`, while Ubuntu reports all four `TRUE`.
The images install `R-dev` but never the graphics headers, and R's `configure` treats those as optional and does not fail when they are absent, so the build succeeds and ships an R that cannot draw.

Reproduced in a clean `alpine:3.22` container with the old package set:

```
Additional capabilities:  PNG, NLS, ICU
Capabilities skipped:     JPEG, TIFF, cairo
```

One correction to the original diagnosis: `--with-x=no` was not the cause, and libpng was in fact found.
R's bitmap and `pangocairo` checks run independently of `R_X11` (`configure.ac:2604` gates on `want_cairo`, not `use_X11`).
`capabilities("png")` needs a device *backend*, and with X11 off and cairo absent there was none, which is why all four read `FALSE` despite configure listing PNG.
So the fix is purely the missing `-dev` packages.
X11 stays off, which is correct for headless images, and cairo covers `png()` / `jpeg()` / `tiff()` / `svg()`.

## Changes

- `builder/Dockerfile.alpine-{320,321,322,323,324}` — install `pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev`; pass `--with-cairo --with-libpng --with-jpeglib --with-libtiff` explicitly so the intent sits next to `--with-x=no`; set `REQUIRED_CAPABILITIES`.
- `builder/build.sh` — add `verify_capabilities()` between `compile_r` and `package_r`. A build that loses a graphics device now fails instead of being packaged and uploaded. Opt-in via `REQUIRED_CAPABILITIES`, so every non-Alpine platform is untouched.
- `.crow/build.yaml` — add a `FORCE_REBUILD` escape hatch to the dedup step. Artifact filenames carry only the R version, so the HEAD probe would otherwise keep skipping every Alpine version and serving the stale broken binaries.
- `CLAUDE.md` — record the three gotchas.

## Verification

Compiled R 4.5.1 in the patched `alpine-322` image, through the real `build.sh`:

```
       jpeg         png        tiff       tcltk         X11        aqua
       TRUE        TRUE        TRUE        TRUE       FALSE       FALSE
        NLS       Rprof     profmem       cairo         ICU long.double
       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
All required capabilities are present.
```

The devices actually render, not just report `TRUE` (`default bitmapType: cairo`):

```
png   -> t.png (2154 bytes)
jpeg  -> t.jpeg (4489 bytes)
tiff  -> t.tiff (120160 bytes)
svg   -> t.svg (9381 bytes)
```

The guard was exercised in both directions against that real build: it passes on the four graphics capabilities, and returns non-zero naming the missing entry when additionally asked for `X11`.
`crow lint .crow/` passes and `bash -n builder/build.sh` is clean.

## Behaviour change

Alpine R binaries gain the cairo, png, jpeg and tiff devices, and link against `libcairo`, `libpangocairo`, `libpng`, `libjpeg` and `libtiff`.
The `.apk` metadata already declared those runtime dependencies, so consumer images need no change.
Any Alpine build that loses a graphics device now fails the pipeline rather than uploading silently.

**Needs a follow-up after merge:** the first run must have `FORCE_REBUILD` set, otherwise dedup skips every existing Alpine version and the broken artifacts stay in the bucket.

Reviewed-on: #9
This commit is contained in:
Patrick Schratz 2026-09-18 07:04:22 +00:00 • committed by Patrick Schratz
commit 1362e0bd3a
8 changed files with 130 additions and 11 deletions

View file

@ -178,12 +178,22 @@ steps:
esac
BASE="https://s3.eu-central-003.backblazeb2.com/devxy-r-builds/${PLATFORM_ID}"
: > r-versions-existing.txt
for VERSION in $(cat r-versions-to-build.txt); do
URL="$BASE/$(printf "$FMT" "$VERSION" "${ARCH_ID}")"
if [ "$(curl -s -o /dev/null -w '%{http_code}' -I "$URL")" = "200" ]; then
echo "$VERSION" >> r-versions-existing.txt
fi
done
# Escape hatch for when the builder image itself changes in a way that
# alters the resulting R binary (a newly enabled graphics device, a
# different BLAS). The artifact filename carries only the R version, so
# dedup would otherwise keep the stale binaries forever. Set FORCE_REBUILD
# to a non-empty value as a pipeline variable on a manual run, or hardcode
# it here temporarily; uploads overwrite in place.
if [ -n "$FORCE_REBUILD" ]; then
echo "FORCE_REBUILD is set, ignoring artifacts already in the bucket"
else
for VERSION in $(cat r-versions-to-build.txt); do
URL="$BASE/$(printf "$FMT" "$VERSION" "${ARCH_ID}")"
if [ "$(curl -s -o /dev/null -w '%{http_code}' -I "$URL")" = "200" ]; then
echo "$VERSION" >> r-versions-existing.txt
fi
done
fi
- echo "Already present in s3:"; cat r-versions-existing.txt
backend_options:
kubernetes:

View file

@ -10,4 +10,11 @@ CI pipelines (Crow, in `.crow/`) that build R binaries and upload them to Backbl
## Gotchas
- **B2 requires authentication for the list-bucket API.** Anonymous GET only works for individual public-read objects — an empty bucket listing usually means missing credentials, not an empty bucket. This silently broke rebuild dedup once.
- **R's configure silently disables graphics devices when headers are missing.**
It never fails the build, so a missing `-dev` package yields a working R whose `capabilities()` reports `cairo`, `png`, `jpeg` and `tiff` as `FALSE`.
Installing the runtime libraries on the target system afterwards cannot bring compiled-out devices back; the binary has to be rebuilt.
`builder/build.sh` therefore asserts `REQUIRED_CAPABILITIES` (set per Dockerfile) after `make install`.
- **The `--with-x=no` on the Alpine images does not disable cairo.** R's bitmap and pangocairo checks run independently of `R_X11`, so `png()` and `svg()` work headless via cairo.
- **Artifact filenames carry only the R version, not the builder image.**
When a builder change alters the resulting binary, dedup would keep serving the stale artifact forever; set `FORCE_REBUILD` in `.crow/build.yaml` to rebuild and overwrite in place.
- When a pipeline fails, fetch the Crow logs yourself instead of asking the user to paste them, and monitor reruns in the background until green.

View file

@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-320
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-320 /package.sh
COPY build.sh .

View file

@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-321
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-321 /package.sh
COPY build.sh .

View file

@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-322
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-322 /package.sh
COPY build.sh .

View file

@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-323
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-322 /package.sh
COPY build.sh .

View file

@ -5,6 +5,13 @@ ENV OS_IDENTIFIER alpine-324
RUN set -x \
&& apk add -q R-dev curl ca-certificates bash g++ tzdata openjdk17 texmf-dist texlive-full tar sed patch tcl tk tk-dev xvfb libdeflate libdeflate-dev
# Graphics devices. R's configure only enables the cairo/png/jpeg/tiff devices
# when the corresponding headers are present at compile time, and pkgconf must
# exist for the pangocairo check to run at all. Without these, capabilities()
# reports cairo/png/jpeg/tiff as FALSE, and installing the runtime libraries
# afterwards cannot bring the compiled-out devices back.
RUN apk add -q pkgconf cairo-dev pango-dev fontconfig-dev freetype-dev libpng-dev jpeg-dev tiff-dev zlib-dev
# Install s5cmd for S3 uploads (much faster than AWS CLI)
RUN ARCH=$(uname -m); if [ "$ARCH" = "x86_64" ]; then S5CMD_ARCH="64bit"; else S5CMD_ARCH="arm64"; fi && \
curl -sL "https://github.com/peak/s5cmd/releases/download/v2.3.0/s5cmd_2.3.0_Linux-${S5CMD_ARCH}.tar.gz" | tar xz -C /usr/local/bin s5cmd
@ -18,7 +25,12 @@ RUN chmod 0777 /opt
# Override the default pager used by R
ENV PAGER /usr/bin/pager
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-blas --with-lapack"
# X11 stays off: these are headless images, and the cairo/bitmap devices are
# detected independently of X11, so png()/svg() still work via cairo.
ENV CONFIGURE_OPTIONS "--enable-R-shlib --with-tcltk --enable-memory-profiling --with-x=no --with-cairo --with-libpng --with-jpeglib --with-libtiff --with-blas --with-lapack"
# Fail the build if a graphics device silently drops out again.
ENV REQUIRED_CAPABILITIES "cairo,png,jpeg,tiff"
COPY package.alpine-324 /package.sh
COPY build.sh .

View file

@ -209,6 +209,47 @@ local({
EOF
}
# verify_capabilities()
# Guard against a graphics device being silently compiled out. R's configure
# only enables the cairo/png/jpeg/tiff devices when the matching headers were
# present at compile time, and it does not fail when they are missing, so a
# missing -dev package produces a working R that simply cannot draw. Once that
# tarball is published, installing the runtime libraries on the target system
# cannot bring the devices back; the build has to be redone.
#
# Dockerfiles opt in by setting REQUIRED_CAPABILITIES to a comma-separated list
# of capabilities() names, e.g. "cairo,png,jpeg,tiff".
verify_capabilities() {
if [ -z "${REQUIRED_CAPABILITIES}" ]; then
return 0
fi
echo "Verifying required R capabilities: ${REQUIRED_CAPABILITIES}"
# The full capabilities() table goes to stderr so it shows up in the build
# log; stdout carries only the space-separated list of missing entries.
local missing
missing=$("${R_INSTALL_PATH}/bin/Rscript" --vanilla -e '
required <- trimws(strsplit(Sys.getenv("REQUIRED_CAPABILITIES"), ",")[[1]])
required <- required[nzchar(required)]
caps <- capabilities()
writeLines(capture.output(print(caps)), con = stderr())
ok <- (required %in% names(caps)) & (unname(caps[required]) %in% TRUE)
cat(paste(required[!ok], collapse = " "), "\n", sep = "")
') || {
echo "ERROR: could not query capabilities() from the freshly built R" >&2
return 1
}
if [ -n "${missing}" ]; then
echo "ERROR: R ${R_VERSION} for ${OS_IDENTIFIER} is missing required capabilities: ${missing}" >&2
echo "ERROR: install the matching -dev packages in builder/Dockerfile.${OS_IDENTIFIER} and rebuild." >&2
return 1
fi
echo "All required capabilities are present."
}
# check for packager script
## If it exists this build is ready for packaging with nFPM, so run the script
## else do nothing
@ -236,6 +277,7 @@ set_up_environment
fetch_r_source $R_VERSION
patch_r $R_VERSION
compile_r $R_VERSION
verify_capabilities
package_r $R_VERSION
archive_r
upload_r $R_VERSION