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fix(rccl): add weak stubs for ppc64le TOC-surviving symbols - #14913
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…ests On ppc64le, TOC references to extern symbols survive --gc-sections even when the code path referencing them is dead. Add weak stub definitions for topoPathTypeStr, network device-count functions, and GIN plugin functions so host-only test binaries link without GPU/network libraries. Co-Authored-By: Claude <noreply@anthropic.com>
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Findings
3 more finding(s), not posted inline
projects/rccl/test/host/fakes/nccl_fakes.cc:658(Low) #ifndef RCCL_NCCL_FAKES_OMIT_GRAPH excludes MicroGraph, the opposite of the description, and every other binary using topoPathTypeStr already links a strong copy, so this weak copy looks unused; drop it or name the target that needs it.projects/rccl/test/host/fakes/transport_stubs.cc:389(Low) The five extern "C" stubs (ncclNetIb_devices and the rest) name symbols nothing in projects/rccl references, topo.cc included; remove the block.projects/rccl/test/host/fakes/transport_stubs.cc:399(Low) Dev-count stubs return success with 0 devices in a fail-loud stub file (lines 7-11), and lines 394-397 exceed 120 columns; call FailLoudUnfaked instead.
Bottom line: Looks approval ready; the inline notes are small cleanups to the new ppc64le stubs.
Comment @argus review to re-run, or @argus re-review after pushing.
| // topo.cc stores ncclNetGetDevCount / ncclGinGetDevCount / etc. as function | ||
| // pointers in netInfo; the TOC entry survives --gc-sections on POWER even | ||
| // when the code path is dead. Weak stubs let MicroGraph (which links the | ||
| // real topo.cc but not graph_fakes.cc) resolve them. |
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Low
Lines 390-393 restate the TOC note at lines 375-379, so they can go.
Suggested change
| // real topo.cc but not graph_fakes.cc) resolve them. |
mch
approved these changes
Nov 3, 2026
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TheRock Submodule Bump ActivityNewest first
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Motivation
Part of work for ROCm/TheRock#5518
Replaces #13502 which is now stale (upstream changes caused conflicts and a duplicate symbol).
On ppc64le, the POWER ABI's TOC (Table of Contents) keeps references to extern symbols alive through
--gc-sections, even when the code path referencing them is dead. This causes undefined-symbol link errors in host-only micro test binaries that link production source files (topo.cc, rome_models.cc) but not the GPU/network libraries that provide the symbols.Technical Details
Add weak stub definitions guarded by
__powerpc64__/__PPC64__in two test fake files:nccl_fakes.cc:topoPathTypeStr[](referenced by rome_models.cc). Guarded byRCCL_NCCL_FAKES_OMIT_GRAPHso it only applies when the graph fakes are excluded (e.g.rccl-UnitTestsMicroGraph).transport_stubs.cc: Plugin device-count and network functions referenced as function pointers in topo.cc:ncclNetIb_devices,ncclNetGdrCopy_devices,ncclNetSocket_devicesncclGinDeviceCount,ncclGinCustomAllReduceDeviceCountncclNetGetDevCount,ncclCollNetGetDevCount,ncclGinGetDevCount,ncclRmaGetDevCountncclNetSetVirtDevCount,ncclCollNetSetVirtDevCountAll stubs use
__attribute__((weak))so tests that supply their own strong definitions (e.g.gin-plugin-init-test,graph_fakes.cc) win without duplicate-symbol errors.x86_64 builds are unaffected — the
#if defined(__powerpc64__)guard ensures the stubs are only compiled on POWER.Test Plan
Built RCCL on a POWER10 ppc64le machine via TheRock. Ran the host microtest suites (
ctest -R "Micro|HostOnly|MicroTopo").Test Result
All micro test binaries link and run. 137/153 ctest targets pass. Remaining failures are pre-existing and unrelated (divide-by-zero death test on POWER, groupJob logic bug).