proc_waiter: error on read of child wait pipe 0x0, Win32 error 6

[Jay K]

I get this a lot:

      0 [waitproc] cm3 7641 proc_waiter: error on read of child wait pipe 0x0, Win32 error 6
    452 [waitproc] cm3 7641 proc_waiter: error on read of child wait pipe 0x0, Win32 error 6
    716 [waitproc] cm3 7641 proc_waiter: error on read of child wait pipe 0x0, Win32 error 6
   1652 [waitproc] cm3 7641 proc_waiter: error on read of child wait pipe 0x0, Win32 error 6
      0 [main] sh 7775 C:\cygwin64\bin\sh.exe: *** fatal error - internal error reading the windows environment - too many environment variables?

Scenario is multi-threaded "launching" a bunch of invocations of gcc.
"launching" was usually spawnve or fork/execve but I changed the code to use system and it still happens.
I might try to make a small reproducing, if this is not known.
It seems a bit difficult to believe I could cause this internal looking error.

Thank you,
 - Jay