IO library locking doesn't count readers

We aren't keeping track of the number of readers of a file, so that the first one to close a Handle removes the lock.

> main = do
>         fc <- openFile "z" ReadMode   -- sacrificial handle
>         fr <- openFile "z" ReadMode
>         hClose fc
>         fa <- openFile "z" AppendMode
>         hPutStr fa "append this line\n"
>         hGetLine fr >>= print

this should fail.

Trac metadata

Trac field	Value
Version	6.4.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	lowest
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown

changed weight to 0

added Tbug Trac import labels

changed title from IO library locking bug to IO library locking doesn't count readers

mentioned in commit 10db1142

changed milestone to %6.6.1

Trac metadata

Trac field	Value
Test case	- → countReaders001

mentioned in commit 35aa7715

removed milestone

changed milestone to %6.8.3

assigned to @simonmar

See also #1109 (closed). Locking could be changed to use a hash table, that would make things much easier.

and #1753 (closed)

mentioned in commit 5f59f657

mentioned in commit 1d026619

closed

Fixed, see #1109 (closed).

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

Trac metadata

Trac field	Value
Architecture	Unknown → Unknown/Multiple

Trac metadata

Trac field	Value
Operating system	Unknown → Unknown/Multiple

added Plow label