cuiziweizw opened a new pull request, #18019:
URL: https://github.com/apache/nuttx/pull/18019
## Summary
This PR adds the `_LIBCPP_HAS_NO_CONTENTION_TABLE` macro definition to the
libcxx configuration file.
### Why this change is needed
By default, libcxx allocates a contention table for optimizing semaphore
operations under high contention scenarios. However, for memory-constrained
embedded systems like NuttX targets, this table consumes valuable RAM that
could be better used elsewhere.
### What this PR does
- Adds `#define _LIBCPP_HAS_NO_CONTENTION_TABLE` to
`libs/libxx/__config_site`
- This disables the contention table allocation in libcxx's semaphore
implementation
- Results in reduced RAM footprint without affecting basic semaphore
functionality
## Impact
- **Stability**: No impact - this is a standard libcxx configuration option
- **Compatibility**: No breaking changes - semaphores continue to work
correctly
- **RAM Savings**: Reduces memory footprint by eliminating the contention
table
- **Performance**: Minimal impact for typical embedded workloads with low
thread contention
## Testing
### Build Verification
- **Host**: Ubuntu Linux x86_64
- **Build System**: CMake/Make
The change was verified by confirming successful compilation with the new
configuration.
```bash
# Configure and build
<board>:<config>
make -j$(nproc)
# Build completed successfully without errors
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