Gsoc26 blog post 1

content/blog/2026-06-19-gsoc-app-compat-library-upgrades.mdx

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+---
+title: "GSoC'26: Upgrading Application Library Ports to Newer Upstream Versions"
+description: |
+  A technical update on the first three weeks of Google Summer of Code 2026 with
+  Unikraft, covering the upgrade of SQLite, Lua, and Redis library ports, as well
+  as two core bug fixes discovered along the way.
+publishedDate: 2026-06-19
+authors:
+- RaduAndreiTudorica
+tags:
+- gsoc
+- gsoc2026
+- lib-ports
+- sqlite
+- lua
+- redis
+---
+
+## Project Overview
+
+My Google Summer of Code 2026 project focuses on upgrading Unikraft's application library ports to their latest upstream versions.
+Unikraft maintains ports of widely used libraries — such as SQLite, Lua, Redis, Nginx, Python3, and libgo — that enable applications to run as unikernels.
+As upstream projects release new versions, these ports must be updated to stay current.
+The goal is to systematically upgrade each library port, resolve any build and runtime issues that arise, and validate that the resulting unikernels function correctly.
+
+## Work Completed
+
+### lib-sqlite: Upgrade from `3.40.1` to `3.53.1`
+
+SQLite `3.53.1` is the latest stable release.
+The upgrade required updating the version, SHA256 checksum, and download URL in `Library.uk` and `Makefile.uk`.
+
+During testing, `stdout` was not appearing on the serial console.
+After investigation (and help from Stefan Jumarea), the fix was enabling `CONFIG_LIBPOSIX_TTY_STDOUT_SERIAL` in the defconfig for the SQLite application in `catalog-core`.
+This option was missing and is likely absent in other application defconfigs as well.
+
+Relevant pull requests:
+
+- [lib-sqlite#12](https://github.com/unikraft/lib-sqlite/pull/12): version bump
+- [catalog-core#106](https://github.com/unikraft/catalog-core/pull/106): add `CONFIG_LIBPOSIX_TTY_STDOUT_SERIAL` to SQLite defconfig
+
+Tested with `kraft build` and `kraft run` using the `catalog/library/sqlite` application.
+A SELECT query on the Chinook sample database returned the expected 10 rows.
+
+### lib-lua: Upgrade from `5.4.4` to `5.4.8`
+
+Lua `5.4.8` is the latest release in the `5.4` series.
+The upgrade followed the same pattern as SQLite:
+updating the version string and SHA256 in `Library.uk`, and the version variable in `Makefile.uk`.
+
+Relevant pull request:
+
+- [lib-lua#12](https://github.com/unikraft/lib-lua/pull/12): version bump
+
+Tested with `kraft build` and `kraft run` using the `catalog/library/lua/5.4` application.
+The `helloworld.lua` example ran successfully.
+
+### lib-redis: Upgrade from `7.0.11` to `8.0.2`
+
+Redis `8.0.2` is the most significant upgrade in the project.
+Redis 8 introduced substantial changes to the codebase between versions `7.0.11` and `8.0.2`, requiring several non-trivial modifications:
+
+**Patch changes:**
+
+- Dropped patch `0001` (un/likely macro redefinition guards): Redis 8 defines these macros upstream, so the patch caused a redefinition error and was removed.
+- Rewrote patch `0002` (bytesToHuman static linkage): the function signature changed in Redis 8 — both the return type (now `char *` in `redis-cli.c`) and the addition of a `size_t size` parameter — so the patch was updated to match the new signatures.
+
+**New source files:**
+
+Redis 8 added 13 new `.c` files that were not present in the `Makefile.uk` source list:
+`cluster_legacy.c`, `crccombine.c`, `ebuckets.c`, `eventnotifier.c`, `iothread.c`, `kvstore.c`, `logreqres.c`, `lolwut8.c`, `mstr.c`, `socket.c`, `strl.c`, `threads_mngr.c`, and `unix.c`.
+
+**C++ dependency (fast_float + fpconv):**
+
+Redis 8 introduced a new double-conversion path using `deps/fast_float/` and `deps/fpconv/`.
+`fast_float_strtod.cpp` is a C++ source file, requiring:
+
+- `LIBREDIS_CXXINCLUDES-y` entries for the `fast_float` headers and the compiler intrinsics directory (using `$(shell $(CC) -print-file-name=include)` for portability).
+- Adding `fast_float_strtod.cpp` and `fpconv_dtoa.c` to `LIBREDIS_SRCS-y`.
+- Linking the C++ runtime libraries (`libcxx`, `libcxxabi`, `libunwind`, `compiler-rt`) in the application Kraftfile.
+
+**AVX2 guard:**
+
+Redis 8's `config.h` automatically defines `HAVE_AVX2` on GCC ≥ 5 targeting x86_64, which causes build failures on platforms without AVX2 support.
+Adding `-UHAVE_AVX2` to `LIBREDIS_FLAGS_SUPPRESS` prevents this.
+
+**release.h generation:**
+
+Redis 8 requires `src/release.h` to be generated by `mkreleasehdr.sh` before compilation.
+A `UK_PREPARE` rule was added to `Makefile.uk` to run this script automatically.
+
+Relevant pull request:
+
+- [lib-redis#17](https://github.com/unikraft/lib-redis/pull/17): full upgrade
+
+Tested on Unikraft stable (RELEASE-`0.21.0` Ijiraq) with `qemu/x86_64`.
+The unikernel boots, loads the configuration file, and reaches `Ready to accept connections`.
+The basic `redis-cli` commands respond as expected (connectivity check, write, and read-back).
+
+## Core Bug Fixes
+
+While working on the Redis upgrade, two bugs in the Unikraft core were identified and fixed.
+
+### Missing `extern "C"` guard in platform PAL headers
+
+When adding the `fast_float` C++ dependency to Redis 8, building `libcxxabi` (required for C++ runtime support) failed with:
+
+```text
+ukpal/include/uk/pal/ectx.h:63: error: conflicting declaration of
+'void uk_pal_ectx_sanitize(uk_pal_ectx*)' with 'C' linkage
+plat/native/pal/include/uk/plat/pal/ectx.h:28: note: previous
+declaration with 'C++' linkage
+```
+
+The root cause is that `plat/native/pal/include/uk/plat/pal/ectx.h` and `plat/xen/pal/include/uk/plat/pal/ectx.h` define `uk_pal_ectx_*` functions as `static inline` without an `extern "C"` guard.
+When these headers are included from C++ translation units (via `libcxxabi/cxa_guard.cpp` → `uk/syscall.h` → `uk/arch/ctx.h` → `uk/lcpu/ectx.h`), the functions receive C++ linkage, conflicting with the `extern "C"` declarations in `ukpal/include/uk/pal/ectx.h`.
+
+The issue reproduces on a clean `helloworld-cpp` build on both stable and staging, confirming it is not specific to the Redis port.
+
+The fix adds an `#ifdef __cplusplus` / `extern "C"` guard to both platform headers, consistent with `ukpal/ectx.h`.
+
+Relevant pull request:
+
+- [unikraft/unikraft#1832](https://github.com/unikraft/unikraft/pull/1832)
+
+## Next Steps
+
+- **Nginx**: upgrade the lib-nginx port to the latest stable version.
+- **Python3**: upgrade the lib-python3 port.
+- **libgo**: upgrade the libgo port (most complex, due to Go toolchain dependencies).
+
+## Acknowledgements
+
+Special thanks to Razvan Deaconescu, Stefan Jumarea, and Sriprad Potukuchi for their guidance, quick feedback, and for identifying the correct direction when issues arose.