casaroli opened a new pull request, #20816:
URL: https://github.com/apache/nuttx/pull/20816
## Summary
CMake saves `CMAKE_AR` and `CMAKE_RANLIB` of the first configure in
`CMakeFiles/<version>/CMake<LANG>Compiler.cmake`. On each later configure,
CMake reads this file after the toolchain file, so the saved tools replace the
tools that the toolchain file selects.
The arm, arm64 and risc-v GCC toolchain files select `gcc-ar` (arm and
risc-v also `gcc-ranlib`) only when LTO is on. When LTO is enabled in an
existing build directory (menuconfig, kconfig-tweak), the archive rules keep
the plain `ar` and `ranlib`. Without the LTO plugin, the archive index has no
symbols of the LTO objects, and the linker takes no member from the libraries.
On arm the link warns `cannot find entry symbol __start` and writes an empty
`nuttx`, or stops with `undefined reference to 'arm_boot'` from `arm_head.S`.
This PR puts the tools that the toolchain file selects in the archive rules
(`${CMAKE_AR}`, `${CMAKE_RANLIB}`) instead of the `<CMAKE_AR>` and
`<CMAKE_RANLIB>` placeholders. The toolchain file runs on each configure after
`.config` is read, so the rules follow the current LTO options.
## Impact
CMake builds that enable LTO after the first configure: the libraries get an
LTO symbol index and the image links. A first configure gives the same rules as
before, so builds without LTO and defconfigs with LTO do not change. arm64
always runs `gcc-ranlib`, so it linked correctly before; it now also archives
with `gcc-ar`. risc-v linked correctly before only with a toolchain that
installs the LTO plugin in `lib/bfd-plugins` (xPack does, Arm GNU does not). No
documentation change is necessary.
## Testing
CMake, configure the defconfig, then `kconfig-tweak --enable LTO_FULL
--disable LTO_NONE` and build. Arm GNU 13.2.rel1 (arm-none-eabi), 14.2.rel1
(aarch64-none-elf), xPack 14.3.0-1 (riscv-none-elf), CMake 4.3.1, macOS.
| config | master | this PR |
|---|---|---|
| `mps2-an500:nsh` (armv7-m) | `cannot find entry symbol __start`, text 0 |
text 348968, boots, `hello` runs, `ostest` runs as without LTO |
| `mps2-an521:nsh` (armv8-m) | `cannot find entry symbol __start`, text 0 |
text 322060, boots, `hello` runs |
| `nucleo-f429zi:nsh` (armv7-m) | `cannot find entry symbol __start`, text 0
| text 166888, `__start` and `_vectors` present |
| `nucleo-l552ze:nsh` (armv8-m) | `cannot find entry symbol __start`, text 0
| text 204848, `__start` and `_vectors` present |
| `qemu-armv7a:nsh` | `undefined reference to 'arm_boot'`, `'nx_start'` |
text 315372, boots, `hello` runs |
| `qemu-armv8a:nsh` | text 294506 | text 294506, boots, `hello` runs |
| `rv-virt:nsh` | text 207906 | text 207906, boots, `hello` runs |
The archive rule on master is `arm-none-eabi-ar rcs ... &&
arm-none-eabi-ranlib`; with this PR it is `arm-none-eabi-gcc-ar rcs ... &&
arm-none-eabi-gcc-ranlib`.
No change for the other builds (master and this PR give the same sizes):
CMake without LTO for `mps2-an500:nsh`, `qemu-armv7a:nsh`, `qemu-armv8a:nsh`
and `rv-virt:nsh`; Make with LTO for `mps2-an500:nsh` (text 347050); and CMake
`nucleo-g431rb:nsh`, which has LTO in its defconfig (text 129090).
`ostest` on `mps2-an500:nsh` stops at the same assertion with and without
LTO (`perf_gettime.c:132`, the performance counter reads 0 under QEMU), so this
PR does not cause it. On `mps2-an521:nsh`, `hello` sometimes hangs under QEMU
also without LTO (1 run in 5).
`tools/checkpatch.sh -c -u -m -g` passes.
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