Posix.popen is broken

Posix.popen hangs if the input is longer than 4096
characters.

For example, attempting to run the attached Haskell
source file will result in the program hanging.  The
program attempts
to use Posix.popen to invoke "cat" without 5000 blank
lines as input.

The problem is that it tries to write to the pipe
before forking.
If there are more than 4096 characters, this will block
until some process reads from the pipe.  But there's
only one process,
so it deadlocks.

Trac metadata

Trac field	Value
Version	None
Type	Bug
TypeOfFailure	OtherFailure
Priority	low
Resolution	ResolvedNoReason
Component	hslibs/posix
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture