CString package:ghc-prim

GHC C strings definitions (previously in GHC.Base). Use GHC.Exts from the base package instead of importing this module directly.

Compute the length of a NUL-terminated string. This address must refer to immutable memory. GHC includes a built-in rule for constant folding when the argument is a statically-known literal. That is, a core-to-core pass reduces the expression cstringLength# "hello"# to the constant 5#.