Failed to create new win32 semaphore on Cygwin

ivmai / bdwgc

The Boehm-Demers-Weiser conservative C/C++ Garbage Collector (bdwgc, also known as bdw-gc, boehm-gc, libgc)

https://www.hboehm.info/gc/

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Failed to create new win32 semaphore on Cygwin #522

Closed ivmai closed 1 year ago

ivmai commented 1 year ago

Build: https://ci.appveyor.com/project/ivmai/bdwgc/builds/45812102/job/hss7251qx96m26tn Host: Win64 Occurrence: ~1/30 Broken commit: d8a88dcd6

gctest ouput: gctest 3718 bdwgc.libs\gctest.exe: *** fatal error in forked process - failed to create new win32 semaphore, currentvalue -1, Win32 error 87 Child process failed, pid= 3718, status= 0x1 Test failed

ivmai commented 1 year ago

Win32 error 87 is ERROR_INVALID_PARAMETER

ivmai commented 1 year ago

According to Cygwin source, the issue occurs during semaphore fixup on fork.

ivmai commented 1 year ago

There are several ways to fix this:

implement directly using Win32 CreateSemaphore (but the risk is leak of handles on fork)
implement some synchronization so that to avoid fork while some thread is being created (complicated synchronization)
use emulation based on mutex and cond (easiest way but unclear whether it is robust against the issue).

Let's the easiest solution and check whether the issue is ever reproduced again.