casaroli opened a new pull request, #20772:
URL: https://github.com/apache/nuttx/pull/20772
## Summary
The make build of `stm32l0538-disco:nsh` (`CONFIG_LTO_FULL`, GNU toolchain)
prints four warnings at the link. This PR fixes their causes, one commit each:
1. `lto-wrapper: warning: Extra option to '-Xassembler': -mthumb, dropping
all '-Xassembler' and '-Wa' options.`
The Makefile of a common board directory includes `$(TOPDIR)/Make.defs`,
and then `board/Make.defs`. The board `Make.defs` of 160 boards included
`$(TOPDIR)/Make.defs` again, so the files of the common directory got the
toolchain flags twice. lto-wrapper then saw different assembler options and
dropped all of them. The commit removes the second include, as the other boards
of these directories do.
2. `lto-wrapper: warning: using serial compilation of 2 LTRANS jobs` (and
its note).
GCC now gets `-flto=auto`, in the make and in the CMake build.
3. `ld: warning: nuttx has a LOAD segment with RWX permissions`.
With LTO, gcc links nuttx. The Makefile gave `-nostdlib` to ld through
`-Xlinker`, so gcc still added its start files and default libraries.
`crtbegin.o` puts an entry into `.init_array`, a writable section, in flash.
gcc now gets `-nostdlib`, as in the CMake build. GNU ld then adds the libgcc
functions that LTO calls only if the link has an object file outside the
libraries, so the link gets an empty object, as the CMake build does with
`empty.c`.
## Impact
Builds with `CONFIG_LTO_FULL` and the GNU toolchain: no start files of the
compiler in the image (a few bytes smaller), and the assembler options are kept
for the files of a common board directory. Other builds do not change, except
that the files of a common board directory no longer get the toolchain flags
twice.
## Testing
GCC 13.2.Rel1 (the CI version) on macOS:
| Build | master | this PR |
|---|---|---|
| `stm32l0538-disco:nsh` (make) | 4 warnings, flash segment `RWE` | no
warning, `R E` |
| `nucleo-g431rb:nsh` (make, LTO) | RWX warning | no warning |
| `stm32l0538-disco:nsh` (CMake) | no warning | no warning |
| `mps2-an500:nsh` with `CONFIG_LTO_FULL` (profiling off), in QEMU | RWX
warning; boots to NSH | no warning; boots to NSH, `uname -a` works |
Builds of `stm32f4discovery:nsh`, `raspberrypi-pico:nsh`, `nrf52840-dk:nsh`,
`samv71-xult:nsh`, `nucleo-h743zi:nsh` and `nucleo-l476rg:nsh` (boards from the
changed common directories) pass, with no new warning.
`tools/checkpatch.sh -c -u -m -g` passes.
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