TeeKen Lau e4f0b4cd96
(doc): set cmake c++ compatible standard when building on MacOS CPU. (#23483)
Signed-off-by: teekenl <teekenlau@gmail.com>
Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
2025-09-16 06:08:46 -07:00

2.7 KiB

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vLLM has experimental support for macOS with Apple Silicon. For now, users must build from source to natively run on macOS.

Currently the CPU implementation for macOS supports FP32 and FP16 datatypes.

!!! warning There are no pre-built wheels or images for this device, so you must build vLLM from source.

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  • OS: macOS Sonoma or later
  • SDK: XCode 15.4 or later with Command Line Tools
  • Compiler: Apple Clang >= 15.0.0

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After installation of XCode and the Command Line Tools, which include Apple Clang, execute the following commands to build and install vLLM from source.

git clone https://github.com/vllm-project/vllm.git
cd vllm
uv pip install -r requirements/cpu.txt
uv pip install -e .

!!! note On macOS the VLLM_TARGET_DEVICE is automatically set to cpu, which is currently the only supported device.

!!! example "Troubleshooting" If the build fails with errors like the following where standard C++ headers cannot be found, try to remove and reinstall your Command Line Tools for Xcode.

```text
[...] fatal error: 'map' file not found
        1 | #include <map>
            |          ^~~~~
    1 error generated.
    [2/8] Building CXX object CMakeFiles/_C.dir/csrc/cpu/pos_encoding.cpp.o

[...] fatal error: 'cstddef' file not found
        10 | #include <cstddef>
            |          ^~~~~~~~~
    1 error generated.
```

---

If the build fails with C++11/C++17 compatibility errors like the following, the issue is that the build system is defaulting to an older C++ standard:

```text
[...] error: 'constexpr' is not a type
[...] error: expected ';' before 'constexpr'
[...] error: 'constexpr' does not name a type
```

**Solution**: Your compiler might be using an older C++ standard. Edit `cmake/cpu_extension.cmake` and add `set(CMAKE_CXX_STANDARD 17)` before `set(CMAKE_CXX_STANDARD_REQUIRED ON)`.

To check your compiler's C++ standard support:
```bash
clang++ -std=c++17 -pedantic -dM -E -x c++ /dev/null | grep __cplusplus
```
On Apple Clang 16 you should see: `#define __cplusplus 201703L`

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