Hadrian: Spurious build failure on fresh build

On a freshly checked-out (Windows10 64)ghc tree I was building with hadrian (hadrian/build.bat -j). It aborted here:

\| Run Ghc CompileHs Stage1: libraries/pretty/src/Text/PrettyPrint/Annotated.hs =\> _build/stage1/libraries/pretty/build/Text/PrettyPrint/Annotated.o
\| Run Ar Pack Stage1: _build/stage1/libraries/stm/build/Control/Concurrent/STM.p_o (and 9 more) =\> _build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a
C:/Users/ggreif/ghc/inplace/mingw/bin/ar.exe: creating _build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a
C:/Users/ggreif/ghc/inplace/mingw/bin/ar.exe: unable to rename '_build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a'; reason: File exists
shakeArgsWith 0.001s 0%
Function shake 0.317s 0%
Database read 0.468s 0%
With database 0.013s 0%
Running rules 3492.921s 99% =========================
Total 3493.720s 100%
Error when running Shake build system:

- _build/stage1/lib/package.conf.d/stm-2.5.0.0.conf
- _build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a

user error (Development.Shake.cmd, system command failed
Command: C:/Users/ggreif/ghc/inplace/mingw/bin/ar.exe q _build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a \@C:\\Users\\ggreif\\AppData\\Local\\Temp\\extA08E
Exit code: 1
Stderr:
C:/Users/ggreif/ghc/inplace/mingw/bin/ar.exe: creating _build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a
C:/Users/ggreif/ghc/inplace/mingw/bin/ar.exe: unable to rename '_build/stage1/libraries/stm/build/libHSstm-2.5.0.0_p.a'; reason: File exists
)

Can this be a concurrency problem, while renaming archives?

Anyway it healed after restarting Hadrian.

Trac metadata

Trac field	Value
Version	8.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System (Hadrian)
Test case
Differential revisions
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Blocking
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Operating system
Architecture