zyfeier opened a new pull request, #21772:
URL: https://github.com/apache/nuttx/pull/21772
## Summary
* Why: the GDB remote protocol and NuttX's internal TCB lookup disagree
about PID 0 - GDB numbers threads from 1, while NuttX reserves PID 0 for the
IDLE task. Mapping GDB thread ids onto NuttX pids with a plain `+1/-1` offset
leaves the idle task reachable through the protocol-side id and lets a protocol
id that hashes to the same pidhash slot shadow the idle task during lookups.
* What: translate the GDB-side thread number into a valid NuttX pid via
PID0_REPLACE (INT32_MAX) at the protocol boundary, so no GDB-visible thread id
ever maps onto the reserved pid 0.
* How: gdb_get_thread(), gdb_query(), gdb_is_thread_active(),
gdb_thread_context() and gdb_send_stop() encode/decode PID0_REPLACE; the old
`pid + 1` / `pid - 1` arithmetic is gone.
## Impact
* Is new feature added? NO - bugfix in existing gdbstub pid handling.
* Impact on user: NO
* Impact on build: NO
* Impact on hardware: gdbstub users only (arm64/arm/risc-v boards with
CONFIG_SERIAL_GDBSTUB).
* Impact on documentation: NO
* Impact on security: NO
* Impact on compatibility: NO
## Testing
I confirm that changes are verified on local setup and works as intended:
* Build Host(s): Linux x86_64 (Ubuntu 24.04)
* Target(s): syntax-level compile check of libs/libc/gdbstub/lib_gdbstub.c
with the in-tree include environment (gcc -fsyntax-only -Wall -Wshadow, clean).
Testing logs (compile check):
```
$ gcc -fsyntax-only -fno-strict-aliasing -Wall -Wstrict-prototypes \
-Wshadow -Wundef -I./include -I./sched -I./libs/libc \
-include ./include/nuttx/config.h lib_gdbstub.c
$ echo $?
0
```
Full board builds of the GDBSTUB configs (qemu-armv8a:gdbstub,
stm32f429i-disco:gdbstub) require the aarch64-none-elf toolchain which is
not available on this host; those builds are covered by the repository CI.
Local CI check `tools/checkpatch.sh -c -u -m -g HEAD~1..HEAD` passes.
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