Make sure FlagCX can be compiled on non-NVIDIA platforms

[tengqm]

PR Category

Others

PR Types

Bug Fix

PR Description

When compiling FlagCX on non-NVIDIA platforms, there is an error about the flagcxInnerWindow not defined. This PR fixes the problem.

[Copilot]

Pull request overview

This PR aims to fix a build failure on non-NVIDIA platforms by ensuring flagcxInnerWindow has a concrete definition available when the NVIDIA adaptor headers are not present.

Changes:

• Add a fallback struct flagcxInnerWindow { int winFlags; } definition in sym_heap.h behind a FLAGCX_INNER_WINDOW_DEFINED macro guard.
• Define FLAGCX_INNER_WINDOW_DEFINED in nvidia_adaptor.h to prevent the fallback definition from being used when building with the NVIDIA adaptor.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
flagcx/core/include/sym_heap.h	Adds a guarded fallback definition of flagcxInnerWindow for non-vendor/non-NVIDIA builds.
flagcx/adaptor/include/nvidia_adaptor.h	Defines a macro intended to suppress the fallback flagcxInnerWindow definition when NVIDIA adaptor types are used.

Comments suppressed due to low confidence (1)

flagcx/adaptor/include/nvidia_adaptor.h:32

• FLAGCX_INNER_WINDOW_DEFINED is defined unconditionally here, but the actual flagcxInnerWindow layout differs from the fallback definition added in sym_heap.h when NCCL_VERSION_CODE > 2.27 (this header places base before winFlags). Any TU that sees the fallback definition (because it included sym_heap.h before this header, or never includes this header) but later receives a vendorBase allocated with the NVIDIA layout will misinterpret winFlags.

Consider making winFlags the first member in the NVIDIA flagcxInnerWindow as well (so generic code can safely access it), and/or guarding the macro/struct definition so the type cannot be defined inconsistently depending on include order.

#define FLAGCX_INNER_WINDOW_DEFINED

#if NCCL_VERSION_CODE > NCCL_VERSION(2, 27, 0)

struct flagcxInnerWindow {
  ncclWindow_t base;
  int winFlags;
};

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[MC952-arch]

Please rebase the code