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Update BUILD.md: gplan.so can't be built from source on Bullseye

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Document GLIBC/GLIBCXX version constraints and Python 3.5 compat notes.
Recommend using official release gplan.so instead.
This commit is contained in:
Henrik Muehe
2026-04-30 15:57:31 +02:00
parent eab204b7be
commit 4d2d5fd88c
1 changed files with 42 additions and 17 deletions
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.pi/BUILD.md
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@@ -54,7 +54,23 @@ ELF 32-bit LSB shared object, ARM, EABI5 (linked against libpython3.5m.so.1.0)
```
If you see `ELF 64-bit LSB shared object, ARM aarch64` or `libpython3.9` — wrong.
**Option A: Build from source (recommended)**
**Option A: From official release (recommended)**
```bash
curl -sL https://github.com/OneFinityCNC/onefinity-firmware/releases/download/v1.6.6/onefinity-1.6.6.tar.bz2 \
| tar xjf - --include='*/gplan.so' -O > src/py/camotics/gplan.so
```
The gplan.so is pure G-code planning with no version-specific code — safe to
reuse across firmware versions.
**Option B: From a working Pi**
```bash
scp bbmc@10.1.10.55:/usr/local/lib/python3.5/dist-packages/bbctrl-*.egg/camotics/gplan.so src/py/camotics/
```
**Option C: Build from source (broken — documented for reference)**
Uses Docker's armv7 QEMU emulation on Apple Silicon. Requires a one-time
copy of Python 3.5 headers from the Pi (~1.7MB):
@@ -119,24 +135,23 @@ docker run --rm --platform linux/arm/v7 \
'
```
Why the relink step: SCons compiles `.o` files that are Python-version-agnostic
(they only use `#include <Python.h>` which is ABI-compatible between 3.5-3.9
for the subset camotics uses). The only version-specific part is the final
`-lpython3.X` link. So we let SCons build with 3.9 (since it ignores overrides)
then relink the same objects against 3.5m.
**Why this doesn't actually work:** The `.o` files compile fine and the
Python relink works, but the compiled objects use GLIBC_2.29+ symbols
(from Bullseye's glibc 2.31) and GLIBCXX_3.4.26+ (from GCC 10). The Pi's
Stretch has GLIBC_2.24 / GLIBCXX_3.4.22 max. Even with `-static-libstdc++
-static-libgcc`, glibc symbols like `GLIBC_2.29` leak through the object
files compiled against Bullseye headers.
**Option B: From official release**
To truly build from source you'd need a Stretch armhf container — but
Stretch's archived repos have broken package metadata that prevents
installing build-essential + scons. The official gplan.so was built
in a Raspbian Stretch chroot (see `scripts/gplan-init-build.sh`).
```bash
curl -L https://github.com/OneFinityCNC/onefinity-firmware/releases/download/v1.6.6/onefinity-1.6.6.tar.bz2 \
| tar xjf - --include='*/gplan.so' --strip-components=3 -C src/py/camotics/
```
**Option C: From a working Pi**
```bash
scp bbmc@10.1.10.55:/usr/local/lib/python3.5/dist-packages/bbctrl-*.egg/camotics/gplan.so src/py/camotics/
```
**Key Pi constraints for native code:**
- GLIBC ≤ 2.24 (Stretch)
- GLIBCXX ≤ 3.4.22 (GCC 6)
- Python 3.5m (`libpython3.5m.so.1.0`)
- ELF 32-bit ARM EABI5
### bbserial.ko — kernel module
@@ -230,6 +245,16 @@ Open http://localhost:8765 — full UI with emulated AVR.
See `backup/onefinity-backup.sh` for details. Environment variables: `ONEFINITY_HOST` (default 10.1.10.55), `ONEFINITY_USER` (bbmc), `ONEFINITY_PASS` (onefinity).
## Python 3.5 Compatibility
The Pi runs Python 3.5.3. Watch out for features added in later versions:
- No `f"strings"` (use `"%s" % var` or `"{}".format(var)`)
- No `subprocess.run(capture_output=True)` (use `stdout=PIPE, stderr=PIPE`)
- No `subprocess.run(text=True)` (use `.decode('utf-8')` on stdout/stderr)
- No `dataclasses`, no `:=` walrus operator
- No `asyncio.run()` (use `loop.run_until_complete()`)
- No `typing` generics like `dict[str, int]` (use `Dict[str, int]` from typing)
## Pi Details
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