Incorrect SCC name parsing according to user manual

The user manual says this about SCC names:

The syntax of a cost centre annotation for expressions is

{-# SCC "name" #-} <expression>

where "name" is an arbitrary string, that will become the name of your cost centre as it appears in the profiling output, and <expression> is any Haskell expression.

However GHC is actually more strict about SCC strings, for example, it doesn't accept spaces:

$ cat test.hs
main = {-# SCC "test test" #-} return ()

$ ghc test.hs
[1 of 1] Compiling Main             ( test.hs, test.o )

test.hs:1:16: error: Spaces are not allowed in SCCs
  |
1 | main = {-# SCC "test test" #-} return ()
  |                ^^^^^^^^^^^

It's also possible that GHC is right and user manual is wrong.

Trac metadata

Trac field	Value
Version	8.5
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed milestone to %8.6.1

changed weight to 5

added Tbug Trac import labels

FWIW, here's a 10-years-old program that uses SCC names with spaces: https://github.com/haskell/bytestring/blob/master/tests/Bench.hs

It seems like GHC used to accept this.

The restriction was added 10 years ago to fix #2071 (closed).

See: https://github.com/ghc/ghc/commit/82a7cebaea5dce16fc9658cc6a5ec037348075d1

Trac metadata

Trac field	Value
Related	- → #2071 (closed)

Nice find. I wonder if hp2ps still doesn't handle spaces. May worth checking.

Easiest fix is to update the user manual although I wonder if we should spend some time to actually fix hp2ps. Not sure how hard that would be.

There's also an alternative to hp2ps now: http://hackage.haskell.org/package/hp2pretty perhaps it accepts spaces in identifiers.

changed milestone to %8.8.1

These won't be addressed in GHC 8.6.

changed milestone to %8.10.1

Bumping milestones of low-priority tickets.

added Pnormal label

removed milestone