xiaoxiang781216 opened a new pull request, #20023:
URL: https://github.com/apache/nuttx/pull/20023
## Summary
- C++ strict mode (ISO C++11 and above) drops the GNU `, ##__VA_ARGS__`
comma elision extension, so `GET_ARG_COUNT()` returns 1 instead of 0 for the
zero-argument case, which makes `REVERSE_ARG()` and `FOREACH_ARG()` misselect
their dispatch entry with zero varargs.
- Centralize the empty-argument handling in `GET_ARG_COUNT` (via
`__VA_OPT__` for C++) and make `REVERSE_ARG` and `FOREACH_ARG` dispatch through
`CONCATENATE(prefix, GET_ARG_COUNT(...))`.
- Remove the two duplicated 33-entry selector lists (`REVERSE_ARG_` and
`FOREACH_ARG_`) as a side benefit.
## Impact
- Only `include/nuttx/macro.h` is touched; no new configuration options.
- The C path is unchanged (still uses `, ##__VA_ARGS__`); the C++ path now
uses standard `__VA_OPT__` (available since C++20, and as an extension in GNU
C++ modes of GCC/Clang).
- Users of these macros: `include/nuttx/sched_note.h` (`NOTE_PRINTF_TYPES`,
`NOTE_PRINTF_TAG`), which is exercised by `sched_note_printf()` when
`CONFIG_DRIVERS_NOTE_STRIP_FORMAT` is enabled.
## Testing
Built and booted `sim:nsh` with this change:
```
NuttShell (NSH) NuttX-10.4.0
nsh> uname -a
NuttX 10.4.0 f64dedbe01e Aug 31 2026 17:10:36 sim sim
nsh> echo hello
hello
nsh> ps
TID PID PPID PRI POLICY TYPE NPX STATE EVENT SIGMASK STACK
COMMAND
0 0 0 0 FIFO Kthread - Ready
0000000000000000 0069584 Idle_Task
...
```
Standalone macro test comparing the old and the new header (the
`NOTE_PRINTF_TAG` pattern from `sched_note.h`):
```
$ g++ -std=c++20 test.cpp # old header
tag0=268435456 # GET_ARG_COUNT() == 1, wrong
tag1=268435457
$ g++ -std=c++20 test.cpp # new header
tag0=0 # GET_ARG_COUNT() == 0, correct
tag1=268435457
```
The C behavior is identical before and after the change (`gcc -std=gnu11`
gives `tag0=0` with both headers).
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