【Hackathon 10th Spring No.46】[Build] Windows compilation: platform guards for C++/Python -part1

[cloudforge1]

Motivation

FastDeploy's custom_ops C++ source files include POSIX-only headers (<sys/mman.h>, <sys/ipc.h>, <sys/msg.h>, <unistd.h>) and call POSIX-only APIs (System V IPC, mmap/munmap, shm_open) unconditionally, causing compilation failures on Windows (MSVC). Similarly, Python runtime code uses Linux-specific paths (/dev/shm), process APIs (os.killpg, os.getpgid, os.setsid), and multiprocessing.get_context("fork") — all of which fail on Windows.

This is part of Hackathon 10th Spring No.46: adding Windows build support to FastDeploy.

Related upstream work: PaddlePaddle/Paddle#77690 (Paddle-side phi.lib packaging fix by @ccsuzzh).

Modifications

Part 1: C++ Include Guards + Function Body Guards (26 files, 147+/21-)

• 5 root headers (helper.h, msg_utils.h, save_with_output_msg.h, speculate_msg.h, remote_cache_kv_ipc.h): Wrap POSIX includes with #ifndef _WIN32
• 6 source files with include-only guards (they include POSIX headers but don't call POSIX APIs directly)
• 15 IPC source files (.cc/.cu): Wrap both includes AND function bodies with #ifdef _WIN32 / PD_THROW("... not supported on Windows") / #else / ... / #endif — following the existing pattern in cuda_multiprocess.h

Part 2: Build System (1 file, 8+/2-)

• custom_ops/setup_ops.py: Platform-conditional CUDA link args (-lcuda -lnvidia-ml on Linux, /DEFAULTLIB:cuda.lib /DEFAULTLIB:nvml.lib on Windows)

Part 3: Python Runtime Guards (10 files, 72+/28-)

• Replace 13 hardcoded /dev/shm paths with tempfile.gettempdir() fallback on Windows
• Guard os.killpg/os.getpgid calls with sys.platform check, using p.terminate() on Windows (3 files, 5 sites)
• Guard preexec_fn=os.setsid with conditional kwargs (3 files, 4 sites)
• Use multiprocessing.get_context("spawn") instead of "fork" on Windows (1 site)

Files NOT modified (already Windows-aware): cuda_multiprocess.h, set_data_ipc.cu, unset_data_ipc.cu, cutlass_heuristic.cu, fpA_intB_gemm_template.h

Known limitation: ZMQ IPC transport URIs (ipc:///dev/shm/...) in input processor files are unchanged — they require ZMQ transport-layer changes for full Windows support (future work).

Usage or Command

No new commands. Existing Linux builds are unaffected. On Windows with MSVC + CUDA Toolkit:

python custom_ops/setup_ops.py install

IPC-based operators will raise a clear PD_THROW error on Windows rather than silently failing or producing cryptic MSVC errors.

Accuracy Tests

• No accuracy changes — this PR only adds platform guards
• All existing Linux functionality remains identical (#else branches preserve original code paths exactly)
• IPC ops on Windows will throw a clear error message instead of compilation failure

Checklist

• No POSIX headers included unconditionally on Windows
• IPC function bodies guarded with PD_THROW on Windows (fail loud, not silent)
• Python /dev/shm paths have Windows fallback
• Process management APIs (killpg, setsid, fork) guarded
• Build system link args are platform-conditional
• All pre-commit checks pass (black, isort, flake8, ruff)
• No regressions on Linux (original code paths preserved in #else/else branches)

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 67.21311% with 20 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@b05a6c4). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/engine/common_engine.py	38.46%	6 Missing and 2 partials ⚠️
fastdeploy/engine/engine.py	41.66%	5 Missing and 2 partials ⚠️
fastdeploy/engine/expert_service.py	60.00%	1 Missing and 1 partial ⚠️
fastdeploy/worker/worker_process.py	50.00%	2 Missing ⚠️
fastdeploy/eplb/async_expert_loader.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #6772   +/-   ##
==========================================
  Coverage           ?   72.32%           
==========================================
  Files              ?      394           
  Lines              ?    54305           
  Branches           ?     8507           
==========================================
  Hits               ?    39276           
  Misses             ?    12216           
  Partials           ?     2813           

Flag	Coverage Δ
GPU	72.32% <67.21%> (?)

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