DPH bad sliceP causes RTS panic "allocGroup: requested zero blocks" (#3903) · Issues · Glasgow Haskell Compiler / GHC

DPH bad sliceP causes RTS panic "allocGroup: requested zero blocks"

$ ghci -XPArr
...
Prelude> :m GHC.PArr
Prelude GHC.PArr> sliceP 10 10 [::]
<interactive>: internal error: allocGroup: requested zero blocks
    (GHC version 6.12.1 for i386_apple_darwin)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Abort trap

sliceP 10 10 [::] is bogus. This should have been picked up in the libraries before hitting the RTS assertion.

Trac metadata

Trac field	Value
Version	6.13
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Data Parallel Haskell
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

```
$ ghci -XPArr
...
Prelude> :m GHC.PArr
Prelude GHC.PArr> sliceP 10 10 [::]
<interactive>: internal error: allocGroup: requested zero blocks
    (GHC version 6.12.1 for i386_apple_darwin)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Abort trap
```

`sliceP 10 10 [::]` is bogus. This should have been picked up in the libraries before hitting the RTS assertion.

<details><summary>Trac metadata</summary>

| Trac field             | Value                 |
| ---------------------- | --------------------- |
| Version                | 6.13                  |
| Type                   | Bug                   |
| TypeOfFailure          | OtherFailure          |
| Priority               | normal                |
| Resolution             | Unresolved            |
| Component              | Data Parallel Haskell |
| Test case              |                       |
| Differential revisions |                       |
| BlockedBy              |                       |
| Related                |                       |
| Blocking               |                       |
| CC                     |                       |
| Operating system       |                       |
| Architecture           |                       |

</details>