cjj66619 opened a new pull request, #18887:
URL: https://github.com/apache/nuttx/pull/18887
The sim/src/nuttx-names.in symbol-rename list is the mechanism that keeps
every nuttx libc function used inside nuttx.rel from clashing with the
same-named function in host glibc when the sim executable is finally linked.
The list already covers ~200 symbols (memcpy, strlen, strcat, strchr, ...) but
memchr was missing.
On x86_64 Linux hosts the omission has no visible effect because host glibc
dispatches memchr through an IFUNC resolver (__memchr_ifunc) that the static
libc.a path does not eagerly pull in for typical sim links. On HOST_ARM64
(Ubuntu 20.04 aarch64, glibc 2.31 .. 2.41), however, the final cc/ld invocation
in the sim Makefile drags libc.a(memchr.o) into the link, which then collides
with nuttx libc's lib_memchr.o that has already been folded into nuttx.rel:
/usr/bin/ld:
/usr/lib/gcc/aarch64-linux-gnu/9/../../../aarch64-linux-gnu/libc.a(memchr.o):
in function `__memchr_ifunc':
(.text+0x0): multiple definition of `memchr';
nuttx.rel:libs/libc/string/lib_memchr.c:55: first defined here
Add memchr to the rename list (placed in alphabetical position between
malloc_usable_size and memcpy). After this fix sim:nsh builds cleanly on
aarch64 Linux hosts (verified on NVIDIA Jetson Orin L4T Ubuntu 20.04 +
Raspberry Pi 4B Debian 13 trixie). The behaviour on x86_64 / macOS / Cygwin
hosts is unchanged because those targets either never hit the collision or use
the underscore-prefixed variant gated by NXSYMBOLS macro definition in the same
file (lines 26-31).
# Summary
`arch/sim/src/nuttx-names.in` is the rename-list that prevents nuttx libc
symbols (folded into `nuttx.rel`) from clashing with the same-named symbols
pulled in from host glibc during the final sim link. The list already covers
~200 symbols (`memcpy`, `strlen`, `strcat`, `strchr`, ...) but **`memchr` is
missing**, causing the sim build to fail with a multiple-definition error on
Linux aarch64 hosts.
## Impact
- Affects `sim:nsh`, `sim:nsh2`, `sim:smp`, `sim:bluetooth`, `sim:binder`,
`sim:matter` and any other sim defconfig that includes nuttx libc on an aarch64
Linux host.
- Independent of CPU architecture in principle, but the actual collision
only manifests on aarch64 because x86_64 glibc dispatches `memchr` through an
IFUNC resolver placed in a different static-archive section.
- Concrete environments reproduced: Ubuntu 20.04 L4T (Jetson Orin) and
Debian 13 trixie (Raspberry Pi 4B).
## Root Cause
1. `libs/libc/string/Make.defs:58` unconditionally compiles `lib_memchr.c`.
2. `arch/sim/src/Makefile:436-439` folds `lib_memchr.o` into `nuttx.rel`.
3. `arch/sim/src/Makefile:441` rewrites symbols in `nuttx.rel` via `objcopy
--redefine-syms=nuttx-names.dat` — but `nuttx-names.in` has no
`NXSYMBOLS(memchr)`, so nuttx's `memchr` keeps its original name.
4. `arch/sim/src/Makefile:464-465` runs the final `cc ... nuttx.rel ... -lc
...`. gcc on aarch64 Linux pulls in `libc.a(memchr.o)` (`__memchr_ifunc`),
which collides with nuttx's own `memchr`:
```
/usr/bin/ld: /usr/lib/gcc/aarch64-linux-gnu/9/.../libc.a(memchr.o):
in function `__memchr_ifunc':
(.text+0x0): multiple definition of `memchr';
nuttx.rel:libs/libc/string/lib_memchr.c:55: first defined here
```
## Fix
Single-line addition (between `malloc_usable_size` and `memcpy`, preserving
alphabetical order):
```
+NXSYMBOLS(memchr)
```
After preprocessing this expands to either `memchr NXmemchr` (Linux) or
`_memchr _NXmemchr` (macOS / Cygwin decorated), matching the existing
convention.
## Test results
Verified on:
| Platform | Status |
|---|---|
| NVIDIA Jetson Orin (Ubuntu 20.04 L4T aarch64, GCC 9.4.0, glibc 2.31) |
`sim:nsh` clean build + NSH prompt + `ostest` 38 stages PASS |
| Raspberry Pi 4B (Debian 13 trixie aarch64, glibc 2.41) | Jetson binary
cross-runs ✅ (same ABI) |
`ostest_main: Exiting with status 0` on both platforms. Detailed
reproduction log + bytecount diff in `test-report.md`.
## Companion patch
This patch alone is not sufficient to build `sim:nsh` on Ubuntu aarch64
hosts. A second small fix in `boards/sim/sim/sim/scripts/Make.defs` (gate the
existing `-no-pie` block on `!CONFIG_HOST_ARM64`) is also required. See
companion PR: **`boards/sim: skip -no-pie on HOST_ARM64 to fix sim:nsh link on
aarch64 host`**.
The two PRs are independently mergeable, but on aarch64 you need both to get
a working sim binary.
## checkpatch
`tools/checkpatch.sh -f arch/sim/src/nuttx-names.in` → ✔️ All checks pass.
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