Welcome to the GHC User’s Guide

Contents:

• 1. The Glasgow Haskell Compiler License
• 2. Introduction to GHC
  • 2.1. Obtaining GHC
  • 2.2. Meta-information: Web sites, mailing lists, etc.
  • 2.3. Reporting bugs in GHC
  • 2.4. GHC version numbering policy
• 3. Release notes for version 8.10.1
  • 3.1. Highlights
  • 3.2. Full details
    • 3.2.1. Language
    • 3.2.2. Compiler
    • 3.2.3. GHC API
    • 3.2.4. GHCi
    • 3.2.5. Runtime system
    • 3.2.6. Template Haskell
    • 3.2.7. ghc-prim library
    • 3.2.8. ghc library
    • 3.2.9. base library
    • 3.2.10. Build system
  • 3.3. Included libraries
• 4. Release notes for version 8.10.2
  • 4.1. Highlights
  • 4.2. Full details
    • 4.2.1. Compiler
    • 4.2.2. Runtime system
    • 4.2.3. base library
    • 4.2.4. Build system
  • 4.3. Known issues
  • 4.4. Included libraries
• 5. Release notes for version 8.10.3
  • 5.1. Highlights
  • 5.2. Full details
    • 5.2.1. Compiler
    • 5.2.2. Runtime system
  • 5.3. Known issues
  • 5.4. Included libraries
• 6. Release notes for version 8.10.4
  • 6.1. Bug Fixes
  • 6.2. Known issues
  • 6.3. Included libraries
• 7. Release notes for version 8.10.5
  • 7.1. General bug fixes
  • 7.2. Portability fixes
  • 7.3. Known issues
  • 7.4. Included libraries
• 8. Release notes for version 8.10.6
  • 8.1. General bug fixes
  • 8.2. Packaging fixes
  • 8.3. Portability fixes
  • 8.4. Known issues
  • 8.5. Included libraries
• 9. Using GHCi
  • 9.1. Introduction to GHCi
  • 9.2. Loading source files
    • 9.2.1. Modules vs. filenames
    • 9.2.2. Making changes and recompilation
  • 9.3. Loading compiled code
  • 9.4. Interactive evaluation at the prompt
    • 9.4.1. I/O actions at the prompt
    • 9.4.2. Using do notation at the prompt
    • 9.4.3. Multiline input
    • 9.4.4. Type, class and other declarations
    • 9.4.5. What’s really in scope at the prompt?
      • 9.4.5.1. The effect of :load on what is in scope
      • 9.4.5.2. Controlling what is in scope with import
      • 9.4.5.3. Controlling what is in scope with the :module command
      • 9.4.5.4. Qualified names
      • 9.4.5.5. :module and :load
    • 9.4.6. The :main and :run commands
    • 9.4.7. The it variable
    • 9.4.8. Type defaulting in GHCi
      • 9.4.8.1. Interactive classes
      • 9.4.8.2. Extended rules around default declarations
    • 9.4.9. Using a custom interactive printing function
    • 9.4.10. Stack Traces in GHCi
  • 9.5. The GHCi Debugger
    • 9.5.1. Breakpoints and inspecting variables
      • 9.5.1.1. Setting breakpoints
      • 9.5.1.2. Managing breakpoints
    • 9.5.2. Single-stepping
    • 9.5.3. Nested breakpoints
    • 9.5.4. The _result variable
    • 9.5.5. Tracing and history
    • 9.5.6. Debugging exceptions
    • 9.5.7. Example: inspecting functions
    • 9.5.8. Limitations
  • 9.6. Invoking GHCi
    • 9.6.1. Packages
    • 9.6.2. Extra libraries
  • 9.7. GHCi commands
  • 9.8. The :set and :seti commands
    • 9.8.1. GHCi options
    • 9.8.2. Setting GHC command-line options in GHCi
    • 9.8.3. Setting options for interactive evaluation only
  • 9.9. The .ghci and .haskeline files
    • 9.9.1. The .ghci files
    • 9.9.2. The .haskeline file
  • 9.10. Compiling to object code inside GHCi
  • 9.11. Running the interpreter in a separate process
  • 9.12. Running the interpreter on a different host
  • 9.13. FAQ and Things To Watch Out For
• 10. Using runghc
  • 10.1. Usage
  • 10.2. runghc flags
  • 10.3. GHC Flags
• 11. Using GHC
  • 11.1. Using GHC
    • 11.1.1. Getting started: compiling programs
    • 11.1.2. Options overview
      • 11.1.2.1. Command-line arguments
      • 11.1.2.2. Command line options in source files
      • 11.1.2.3. Setting options in GHCi
    • 11.1.3. Dynamic and Mode options
    • 11.1.4. Meaningful file suffixes
    • 11.1.5. Modes of operation
      • 11.1.5.1. Using ghc --make
      • 11.1.5.2. Expression evaluation mode
      • 11.1.5.3. Batch compiler mode
    • 11.1.6. Verbosity options
    • 11.1.7. Platform-specific Flags
    • 11.1.8. Miscellaneous flags
      • 11.1.8.1. Other environment variables
  • 11.2. Warnings and sanity-checking
  • 11.3. Optimisation (code improvement)
    • 11.3.1. -O*: convenient “packages” of optimisation flags.
    • 11.3.2. -f*: platform-independent flags
  • 11.4. Using Concurrent Haskell
  • 11.5. Using SMP parallelism
    • 11.5.1. Compile-time options for SMP parallelism
    • 11.5.2. RTS options for SMP parallelism
    • 11.5.3. Hints for using SMP parallelism
  • 11.6. Flag reference
    • 11.6.1. Verbosity options
    • 11.6.2. Alternative modes of operation
    • 11.6.3. Which phases to run
    • 11.6.4. Redirecting output
    • 11.6.5. Keeping intermediate files
    • 11.6.6. Temporary files
    • 11.6.7. Finding imports
    • 11.6.8. Interface file options
    • 11.6.9. Recompilation checking
    • 11.6.10. Interactive-mode options
    • 11.6.11. Packages
    • 11.6.12. Language options
    • 11.6.13. Warnings
    • 11.6.14. Optimisation levels
    • 11.6.15. Individual optimisations
    • 11.6.16. Profiling options
    • 11.6.17. Program coverage options
    • 11.6.18. C pre-processor options
    • 11.6.19. Code generation options
    • 11.6.20. Linking options
    • 11.6.21. Plugin options
    • 11.6.22. Replacing phases
    • 11.6.23. Forcing options to particular phases
    • 11.6.24. Platform-specific options
    • 11.6.25. Compiler debugging options
    • 11.6.26. Miscellaneous compiler options
  • 11.7. Running a compiled program
    • 11.7.1. Setting RTS options
      • 11.7.1.1. Setting RTS options on the command line
      • 11.7.1.2. Setting RTS options at compile time
      • 11.7.1.3. Setting RTS options with the GHCRTS environment variable
      • 11.7.1.4. “Hooks” to change RTS behaviour
    • 11.7.2. Miscellaneous RTS options
    • 11.7.3. RTS options to control the garbage collector
    • 11.7.4. RTS options to produce runtime statistics
    • 11.7.5. RTS options for concurrency and parallelism
    • 11.7.6. RTS options for profiling
    • 11.7.7. Tracing
    • 11.7.8. RTS options for hackers, debuggers, and over-interested souls
    • 11.7.9. Getting information about the RTS
  • 11.8. Filenames and separate compilation
    • 11.8.1. Haskell source files
    • 11.8.2. Output files
    • 11.8.3. The search path
    • 11.8.4. Redirecting the compilation output(s)
    • 11.8.5. Keeping Intermediate Files
    • 11.8.6. Redirecting temporary files
    • 11.8.7. Other options related to interface files
    • 11.8.8. Options related to extended interface files
    • 11.8.9. The recompilation checker
    • 11.8.10. How to compile mutually recursive modules
    • 11.8.11. Module signatures
    • 11.8.12. Using make
    • 11.8.13. Dependency generation
    • 11.8.14. Orphan modules and instance declarations
  • 11.9. Packages
    • 11.9.1. Using Packages
    • 11.9.2. The main package
    • 11.9.3. Consequences of packages for the Haskell language
    • 11.9.4. Thinning and renaming modules
    • 11.9.5. Package Databases
      • 11.9.5.1. The GHC_PACKAGE_PATH environment variable
      • 11.9.5.2. Package environments
    • 11.9.6. Installed package IDs, dependencies, and broken packages
    • 11.9.7. Package management (the ghc-pkg command)
    • 11.9.8. Building a package from Haskell source
    • 11.9.9. InstalledPackageInfo: a package specification
  • 11.10. GHC Backends
    • 11.10.1. Native Code Generator (-fasm)
    • 11.10.2. LLVM Code Generator (-fllvm)
    • 11.10.3. C Code Generator (-fvia-C)
    • 11.10.4. Unregisterised compilation
  • 11.11. Options related to a particular phase
    • 11.11.1. Replacing the program for one or more phases
    • 11.11.2. Forcing options to a particular phase
    • 11.11.3. Options affecting the C pre-processor
      • 11.11.3.1. Standard CPP macros
      • 11.11.3.2. CPP and string gaps
    • 11.11.4. Options affecting a Haskell pre-processor
    • 11.11.5. Options affecting code generation
    • 11.11.6. Options affecting linking
  • 11.12. Using shared libraries
    • 11.12.1. Building programs that use shared libraries
    • 11.12.2. Shared libraries for Haskell packages
    • 11.12.3. Shared libraries that export a C API
    • 11.12.4. Finding shared libraries at runtime
      • 11.12.4.1. Unix
      • 11.12.4.2. Mac OS X
  • 11.13. Debugging the compiler
    • 11.13.1. Dumping out compiler intermediate structures
      • 11.13.1.1. Front-end
      • 11.13.1.2. Type-checking and renaming
      • 11.13.1.3. Core representation and simplification
      • 11.13.1.4. STG representation
      • 11.13.1.5. C-- representation
      • 11.13.1.6. LLVM code generator
      • 11.13.1.7. Native code generator
      • 11.13.1.8. Miscellaneous backend dumps
    • 11.13.2. Formatting dumps
    • 11.13.3. Suppressing unwanted information
    • 11.13.4. Checking for consistency
    • 11.13.5. Checking for determinism
    • 11.13.6. Other
• 12. Profiling
  • 12.1. Cost centres and cost-centre stacks
    • 12.1.1. Inserting cost centres by hand
    • 12.1.2. Rules for attributing costs
  • 12.2. Compiler options for profiling
  • 12.3. Time and allocation profiling
    • 12.3.1. JSON profile format
  • 12.4. Profiling memory usage
    • 12.4.1. RTS options for heap profiling
    • 12.4.2. Retainer Profiling
      • 12.4.2.1. Hints for using retainer profiling
    • 12.4.3. Biographical Profiling
    • 12.4.4. Actual memory residency
  • 12.5. hp2ps – Rendering heap profiles to PostScript
    • 12.5.1. Manipulating the hp file
    • 12.5.2. Zooming in on regions of your profile
    • 12.5.3. Viewing the heap profile of a running program
    • 12.5.4. Viewing a heap profile in real time
  • 12.6. Profiling Parallel and Concurrent Programs
  • 12.7. Observing Code Coverage
    • 12.7.1. A small example: Reciprocation
    • 12.7.2. Options for instrumenting code for coverage
    • 12.7.3. The hpc toolkit
      • 12.7.3.1. hpc report
      • 12.7.3.2. hpc markup
      • 12.7.3.3. hpc sum
      • 12.7.3.4. hpc combine
      • 12.7.3.5. hpc map
      • 12.7.3.6. hpc overlay and hpc draft
    • 12.7.4. Caveats and Shortcomings of Haskell Program Coverage
  • 12.8. Using “ticky-ticky” profiling (for implementors)
• 13. Advice on: sooner, faster, smaller, thriftier
  • 13.1. Sooner: producing a program more quickly
  • 13.2. Faster: producing a program that runs quicker
  • 13.3. Smaller: producing a program that is smaller
  • 13.4. Thriftier: producing a program that gobbles less heap space
• 14. GHC Language Features
  • 14.1. Language options
  • 14.2. Unboxed types and primitive operations
    • 14.2.1. Unboxed types
    • 14.2.2. Unboxed type kinds
    • 14.2.3. Unboxed tuples
    • 14.2.4. Unboxed sums
    • 14.2.5. Unlifted Newtypes
  • 14.3. Syntactic extensions
    • 14.3.1. Unicode syntax
    • 14.3.2. The magic hash
    • 14.3.3. Negative literals
    • 14.3.4. Fractional looking integer literals
    • 14.3.5. Binary integer literals
    • 14.3.6. Hexadecimal floating point literals
    • 14.3.7. Numeric underscores
    • 14.3.8. Pattern guards
    • 14.3.9. View patterns
    • 14.3.10. n+k patterns
    • 14.3.11. The recursive do-notation
      • 14.3.11.1. Recursive binding groups
      • 14.3.11.2. The mdo notation
    • 14.3.12. Applicative do-notation
      • 14.3.12.1. Strict patterns
      • 14.3.12.2. Things to watch out for
    • 14.3.13. Parallel List Comprehensions
    • 14.3.14. Generalised (SQL-like) List Comprehensions
    • 14.3.15. Monad comprehensions
    • 14.3.16. New monadic failure desugaring mechanism
    • 14.3.17. Rebindable syntax and the implicit Prelude import
      • 14.3.17.1. Things unaffected by RebindableSyntax
    • 14.3.18. Postfix operators
    • 14.3.19. Tuple sections
    • 14.3.20. Lambda-case
    • 14.3.21. Empty case alternatives
    • 14.3.22. Multi-way if-expressions
    • 14.3.23. Local Fixity Declarations
    • 14.3.24. Import and export extensions
      • 14.3.24.1. Hiding things the imported module doesn’t export
      • 14.3.24.2. Package-qualified imports
      • 14.3.24.3. Safe imports
      • 14.3.24.4. Explicit namespaces in import/export
      • 14.3.24.5. Writing qualified in postpositive position
    • 14.3.25. More liberal syntax for function arguments
      • 14.3.25.1. Changes to the grammar
    • 14.3.26. Summary of stolen syntax
  • 14.4. Extensions to data types and type synonyms
    • 14.4.1. Data types with no constructors
    • 14.4.2. Data type contexts
    • 14.4.3. Infix type constructors, classes, and type variables
    • 14.4.4. Type operators
    • 14.4.5. Liberalised type synonyms
    • 14.4.6. Existentially quantified data constructors
      • 14.4.6.1. Why existential?
      • 14.4.6.2. Existentials and type classes
      • 14.4.6.3. Record Constructors
      • 14.4.6.4. Restrictions
    • 14.4.7. Declaring data types with explicit constructor signatures
    • 14.4.8. Generalised Algebraic Data Types (GADTs)
  • 14.5. Extensions to the record system
    • 14.5.1. Traditional record syntax
    • 14.5.2. Record field disambiguation
    • 14.5.3. Duplicate record fields
      • 14.5.3.1. Selector functions
      • 14.5.3.2. Record updates
      • 14.5.3.3. Import and export of record fields
    • 14.5.4. Record puns
    • 14.5.5. Record wildcards
    • 14.5.6. Record field selector polymorphism
      • 14.5.6.1. Solving HasField constraints
      • 14.5.6.2. Virtual record fields
  • 14.6. Extensions to the “deriving” mechanism
    • 14.6.1. Deriving instances for empty data types
    • 14.6.2. Inferred context for deriving clauses
    • 14.6.3. Stand-alone deriving declarations
    • 14.6.4. Deriving instances of extra classes (Data, etc.)
      • 14.6.4.1. Deriving Functor instances
      • 14.6.4.2. Deriving Foldable instances
      • 14.6.4.3. Deriving Traversable instances
      • 14.6.4.4. Deriving Data instances
      • 14.6.4.5. Deriving Typeable instances
      • 14.6.4.6. Deriving Lift instances
    • 14.6.5. Generalised derived instances for newtypes
      • 14.6.5.1. Generalising the deriving clause
      • 14.6.5.2. A more precise specification
      • 14.6.5.3. Associated type families
    • 14.6.6. Deriving any other class
    • 14.6.7. Deriving strategies
      • 14.6.7.1. Default deriving strategy
    • 14.6.8. Deriving via
  • 14.7. Pattern synonyms
    • 14.7.1. Record Pattern Synonyms
    • 14.7.2. Syntax and scoping of pattern synonyms
    • 14.7.3. Import and export of pattern synonyms
    • 14.7.4. Typing of pattern synonyms
    • 14.7.5. Matching of pattern synonyms
  • 14.8. Class and instances declarations
    • 14.8.1. Class declarations
      • 14.8.1.1. Multi-parameter type classes
      • 14.8.1.2. The superclasses of a class declaration
      • 14.8.1.3. Constrained class method types
      • 14.8.1.4. Default method signatures
      • 14.8.1.5. Nullary type classes
    • 14.8.2. Functional dependencies
      • 14.8.2.1. Rules for functional dependencies
      • 14.8.2.2. Background on functional dependencies
    • 14.8.3. Instance declarations
      • 14.8.3.1. Instance resolution
      • 14.8.3.2. Relaxed rules for the instance head
      • 14.8.3.3. Relaxed rules for instance contexts
      • 14.8.3.4. Instance termination rules
      • 14.8.3.5. Undecidable instances
      • 14.8.3.6. Overlapping instances
      • 14.8.3.7. Instance signatures: type signatures in instance declarations
    • 14.8.4. Overloaded string literals
    • 14.8.5. Overloaded labels
    • 14.8.6. Overloaded lists
      • 14.8.6.1. The IsList class
      • 14.8.6.2. Rebindable syntax
      • 14.8.6.3. Defaulting
      • 14.8.6.4. Speculation about the future
    • 14.8.7. Undecidable (or recursive) superclasses
  • 14.9. Type families
    • 14.9.1. Data families
      • 14.9.1.1. Data family declarations
      • 14.9.1.2. Data instance declarations
      • 14.9.1.3. Overlap of data instances
    • 14.9.2. Synonym families
      • 14.9.2.1. Type family declarations
      • 14.9.2.2. Type instance declarations
      • 14.9.2.3. Closed type families
      • 14.9.2.4. Type family examples
      • 14.9.2.5. Compatibility and apartness of type family equations
      • 14.9.2.6. Decidability of type synonym instances
    • 14.9.3. Wildcards on the LHS of data and type family instances
    • 14.9.4. Associated data and type families
      • 14.9.4.1. Associated instances
      • 14.9.4.2. Associated type synonym defaults
      • 14.9.4.3. Scoping of class parameters
      • 14.9.4.4. Instance contexts and associated type and data instances
    • 14.9.5. Import and export
      • 14.9.5.1. Examples
      • 14.9.5.2. Instances
    • 14.9.6. Type families and instance declarations
    • 14.9.7. Injective type families
      • 14.9.7.1. Syntax of injectivity annotation
      • 14.9.7.2. Verifying the injectivity annotation against type family equations
  • 14.10. Datatype promotion
    • 14.10.1. Motivation
    • 14.10.2. Overview
    • 14.10.3. Distinguishing between types and constructors
    • 14.10.4. Promoted list and tuple types
    • 14.10.5. Promoting existential data constructors
  • 14.11. Kind polymorphism
    • 14.11.1. Overview of kind polymorphism
    • 14.11.2. Overview of Type-in-Type
    • 14.11.3. Principles of kind inference
    • 14.11.4. Inferring the order of variables in a type/class declaration
    • 14.11.5. Complete user-supplied kind signatures and polymorphic recursion
    • 14.11.6. Standalone kind signatures and polymorphic recursion
    • 14.11.7. Standalone kind signatures and declaration headers
    • 14.11.8. Kind inference in closed type families
    • 14.11.9. Kind inference in class instance declarations
    • 14.11.10. Kind inference in type signatures
    • 14.11.11. Explicit kind quantification
    • 14.11.12. Implicit quantification in type synonyms and type family instances
    • 14.11.13. Kind-indexed GADTs
    • 14.11.14. Higher-rank kinds
    • 14.11.15. Constraints in kinds
    • 14.11.16. The kind Type
    • 14.11.17. Inferring dependency in datatype declarations
    • 14.11.18. Inferring dependency in user-written foralls
    • 14.11.19. Kind defaulting without PolyKinds
    • 14.11.20. Pretty-printing in the presence of kind polymorphism
  • 14.12. Levity polymorphism
    • 14.12.1. No levity-polymorphic variables or arguments
    • 14.12.2. Levity-polymorphic bottoms
    • 14.12.3. Printing levity-polymorphic types
  • 14.13. Type-Level Literals
    • 14.13.1. Runtime Values for Type-Level Literals
    • 14.13.2. Computing With Type-Level Naturals
  • 14.14. Equality constraints, Coercible, and the kind Constraint
    • 14.14.1. Equality constraints
    • 14.14.2. Heterogeneous equality
    • 14.14.3. Unlifted heterogeneous equality
    • 14.14.4. The Coercible constraint
    • 14.14.5. The Constraint kind
  • 14.15. Quantified constraints
    • 14.15.1. Motivation
    • 14.15.2. Syntax changes
    • 14.15.3. Typing changes
    • 14.15.4. Superclasses
    • 14.15.5. Overlap
    • 14.15.6. Instance lookup
    • 14.15.7. Termination
    • 14.15.8. Coherence
  • 14.16. Extensions to type signatures
    • 14.16.1. Explicit universal quantification (forall)
    • 14.16.2. The context of a type signature
    • 14.16.3. Ambiguous types and the ambiguity check
    • 14.16.4. Explicitly-kinded quantification
  • 14.17. Lexically scoped type variables
    • 14.17.1. Overview
    • 14.17.2. Declaration type signatures
    • 14.17.3. Expression type signatures
    • 14.17.4. Pattern type signatures
    • 14.17.5. Class and instance declarations
  • 14.18. Bindings and generalisation
    • 14.18.1. Switching off the dreaded Monomorphism Restriction
    • 14.18.2. Let-generalisation
  • 14.19. Visible type application
    • 14.19.1. Inferred vs. specified type variables
    • 14.19.2. Ordering of specified variables
  • 14.20. Implicit parameters
    • 14.20.1. Implicit-parameter type constraints
    • 14.20.2. Implicit-parameter bindings
    • 14.20.3. Implicit parameters and polymorphic recursion
    • 14.20.4. Implicit parameters and monomorphism
  • 14.21. Arbitrary-rank polymorphism
    • 14.21.1. Examples
    • 14.21.2. Type inference
    • 14.21.3. Implicit quantification
  • 14.22. Impredicative polymorphism
  • 14.23. Typed Holes
    • 14.23.1. Valid Hole Fits
      • 14.23.1.1. Refinement Hole Fits
      • 14.23.1.2. Sorting Valid Hole Fits
  • 14.24. Partial Type Signatures
    • 14.24.1. Syntax
      • 14.24.1.1. Type Wildcards
      • 14.24.1.2. Named Wildcards
      • 14.24.1.3. Extra-Constraints Wildcard
    • 14.24.2. Where can they occur?
  • 14.25. Custom compile-time errors
  • 14.26. Deferring type errors to runtime
    • 14.26.1. Enabling deferring of type errors
    • 14.26.2. Deferred type errors in GHCi
    • 14.26.3. Limitations of deferred type errors
  • 14.27. Template Haskell
    • 14.27.1. Syntax
    • 14.27.2. Using Template Haskell
    • 14.27.3. Viewing Template Haskell generated code
    • 14.27.4. A Template Haskell Worked Example
    • 14.27.5. Using Template Haskell with Profiling
    • 14.27.6. Template Haskell Quasi-quotation
  • 14.28. Arrow notation
    • 14.28.1. do-notation for commands
    • 14.28.2. Conditional commands
    • 14.28.3. Defining your own control structures
    • 14.28.4. Primitive constructs
    • 14.28.5. Differences with the paper
    • 14.28.6. Portability
  • 14.29. Bang patterns and Strict Haskell
    • 14.29.1. Bang patterns
    • 14.29.2. Strict-by-default data types
    • 14.29.3. Strict-by-default pattern bindings
    • 14.29.4. Modularity
    • 14.29.5. Dynamic semantics of bang patterns
  • 14.30. Assertions
  • 14.31. Static pointers
    • 14.31.1. Using static pointers
    • 14.31.2. Static semantics of static pointers
  • 14.32. Pragmas
    • 14.32.1. LANGUAGE pragma
    • 14.32.2. OPTIONS_GHC pragma
    • 14.32.3. INCLUDE pragma
    • 14.32.4. WARNING and DEPRECATED pragmas
    • 14.32.5. MINIMAL pragma
    • 14.32.6. INLINE and NOINLINE pragmas
      • 14.32.6.1. INLINE pragma
      • 14.32.6.2. INLINABLE pragma
      • 14.32.6.3. NOINLINE pragma
      • 14.32.6.4. CONLIKE modifier
      • 14.32.6.5. Phase control
    • 14.32.7. LINE pragma
    • 14.32.8. COLUMN pragma
    • 14.32.9. RULES pragma
    • 14.32.10. SPECIALIZE pragma
      • 14.32.10.1. SPECIALIZE INLINE
      • 14.32.10.2. SPECIALIZE for imported functions
    • 14.32.11. SPECIALIZE instance pragma
    • 14.32.12. UNPACK pragma
    • 14.32.13. NOUNPACK pragma
    • 14.32.14. SOURCE pragma
    • 14.32.15. COMPLETE pragmas
    • 14.32.16. OVERLAPPING, OVERLAPPABLE, OVERLAPS, and INCOHERENT pragmas
  • 14.33. Rewrite rules
    • 14.33.1. Syntax
    • 14.33.2. Semantics
    • 14.33.3. How rules interact with INLINE/NOINLINE pragmas
    • 14.33.4. How rules interact with CONLIKE pragmas
    • 14.33.5. How rules interact with class methods
    • 14.33.6. List fusion
    • 14.33.7. Specialisation
    • 14.33.8. Controlling what’s going on in rewrite rules
  • 14.34. Special built-in functions
  • 14.35. Generic classes
  • 14.36. Generic programming
    • 14.36.1. Deriving representations
    • 14.36.2. Writing generic functions
    • 14.36.3. Unlifted representation types
    • 14.36.4. Generic defaults
    • 14.36.5. More information
  • 14.37. Roles
    • 14.37.1. Nominal, Representational, and Phantom
    • 14.37.2. Role inference
    • 14.37.3. Role annotations
  • 14.38. HasCallStack
    • 14.38.1. Compared with other sources of stack traces
  • 14.39. Concurrent and Parallel Haskell
    • 14.39.1. Concurrent Haskell
    • 14.39.2. Software Transactional Memory
    • 14.39.3. Parallel Haskell
    • 14.39.4. Annotating pure code for parallelism
  • 14.40. Safe Haskell
    • 14.40.1. Uses of Safe Haskell
      • 14.40.1.1. Strict type-safety (good style)
      • 14.40.1.2. Building secure systems (restricted IO Monads)
    • 14.40.2. Safe Language
      • 14.40.2.1. Safe Overlapping Instances
    • 14.40.3. Safe Imports
    • 14.40.4. Trust and Safe Haskell Modes
      • 14.40.4.1. Trust check (-fpackage-trust disabled)
      • 14.40.4.2. Trust check (-fpackage-trust enabled)
      • 14.40.4.3. Example
      • 14.40.4.4. Trustworthy Requirements
      • 14.40.4.5. Package Trust
    • 14.40.5. Safe Haskell Inference
    • 14.40.6. Safe Haskell Flag Summary
    • 14.40.7. Safe Compilation
• 15. Foreign function interface (FFI)
  • 15.1. GHC differences to the FFI Chapter
    • 15.1.1. Guaranteed call safety
    • 15.1.2. Varargs not supported by ccall calling convention
  • 15.2. GHC extensions to the FFI Chapter
    • 15.2.1. Unlifted FFI Types
    • 15.2.2. Newtype wrapping of the IO monad
    • 15.2.3. Explicit “forall”s in foreign types
    • 15.2.4. Primitive imports
    • 15.2.5. Interruptible foreign calls
    • 15.2.6. The CAPI calling convention
    • 15.2.7. hs_thread_done()
    • 15.2.8. Freeing many stable pointers efficiently
  • 15.3. Using the FFI with GHC
    • 15.3.1. Using foreign export and foreign import ccall "wrapper" with GHC
      • 15.3.1.1. Using your own main()
      • 15.3.1.2. Making a Haskell library that can be called from foreign code
    • 15.3.2. Using header files
    • 15.3.3. Memory Allocation
    • 15.3.4. Multi-threading and the FFI
      • 15.3.4.1. Foreign imports and multi-threading
      • 15.3.4.2. The relationship between Haskell threads and OS threads
      • 15.3.4.3. Foreign exports and multi-threading
      • 15.3.4.4. On the use of hs_exit()
      • 15.3.4.5. Waking up Haskell threads from C
    • 15.3.5. Floating point and the FFI
    • 15.3.6. Pinned Byte Arrays
• 16. Extending and using GHC as a Library
  • 16.1. Source annotations
    • 16.1.1. Annotating values
    • 16.1.2. Annotating types
    • 16.1.3. Annotating modules
  • 16.2. Using GHC as a Library
  • 16.3. Compiler Plugins
    • 16.3.1. Using compiler plugins
    • 16.3.2. Writing compiler plugins
    • 16.3.3. Core plugins in more detail
      • 16.3.3.1. Manipulating bindings
      • 16.3.3.2. Using Annotations
    • 16.3.4. Typechecker plugins
      • 16.3.4.1. Constraint solving with plugins
    • 16.3.5. Source plugins
      • 16.3.5.1. Parsed representation
      • 16.3.5.2. Type checked representation
      • 16.3.5.3. Evaluated code
      • 16.3.5.4. Interface files
      • 16.3.5.5. Source plugin example
    • 16.3.6. Hole fit plugins
      • 16.3.6.1. Stateful hole fit plugins
      • 16.3.6.2. Hole fit plugin example
    • 16.3.7. Controlling Recompilation
    • 16.3.8. Frontend plugins
    • 16.3.9. DynFlags plugins
• 17. What to do when something goes wrong
  • 17.1. When the compiler “does the wrong thing”
  • 17.2. When your program “does the wrong thing”
• 18. Debugging compiled programs
  • 18.1. Tutorial
  • 18.2. Requesting a stack trace from Haskell code
  • 18.3. Requesting a stack trace with SIGQUIT
  • 18.4. Implementor’s notes: DWARF annotations
    • 18.4.1. Debugging information entities
      • 18.4.1.1. DW_TAG_ghc_src_note
  • 18.5. Further Reading
• 19. Other Haskell utility programs
  • 19.1. “Yacc for Haskell”: happy
  • 19.2. Writing Haskell interfaces to C code: hsc2hs
    • 19.2.1. command line syntax
    • 19.2.2. Input syntax
    • 19.2.3. Custom constructs
    • 19.2.4. Cross-compilation
• 20. Running GHC on Win32 systems
  • 20.1. Starting GHC on Windows platforms
  • 20.2. Running GHCi on Windows
  • 20.3. Interacting with the terminal
  • 20.4. Differences in library behaviour
  • 20.5. File paths under Windows
  • 20.6. Using GHC (and other GHC-compiled executables) with Cygwin
    • 20.6.1. Background
    • 20.6.2. The problem
    • 20.6.3. Things to do
  • 20.7. Building and using Win32 DLLs
    • 20.7.1. Creating a DLL
    • 20.7.2. Making DLLs to be called from other languages
      • 20.7.2.1. Using from VBA
      • 20.7.2.2. Using from C++
• 21. Known bugs and infelicities
  • 21.1. Haskell standards vs. Glasgow Haskell: language non-compliance
    • 21.1.1. Divergence from Haskell 98 and Haskell 2010
      • 21.1.1.1. Lexical syntax
      • 21.1.1.2. Context-free syntax
      • 21.1.1.3. Expressions and patterns
      • 21.1.1.4. Declarations and bindings
      • 21.1.1.5. Typechecking of recursive binding groups
      • 21.1.1.6. Default Module headers with -main-is
      • 21.1.1.7. Module system and interface files
      • 21.1.1.8. Numbers, basic types, and built-in classes
      • 21.1.1.9. In Prelude support
      • 21.1.1.10. The Foreign Function Interface
      • 21.1.1.11. Operator sections
    • 21.1.2. GHC’s interpretation of undefined behaviour in Haskell 98 and Haskell 2010
  • 21.2. Known bugs or infelicities
    • 21.2.1. Bugs in GHC
    • 21.2.2. Bugs in GHCi (the interactive GHC)
• 22. Eventlog encodings
  • 22.1. Event log format
  • 22.2. Runtime system diagnostics
    • 22.2.1. Capability sets
    • 22.2.2. Environment information
    • 22.2.3. Thread and scheduling events
    • 22.2.4. Garbage collector events
    • 22.2.5. Heap events and statistics
    • 22.2.6. Spark events
    • 22.2.7. Capability events
    • 22.2.8. Task events
    • 22.2.9. Tracing events
  • 22.3. Heap profiler event log output
    • 22.3.1. Metadata event types
      • 22.3.1.1. Beginning of sample stream
      • 22.3.1.2. Cost centre definitions
      • 22.3.1.3. Sample event types
      • 22.3.1.4. Cost-centre break-down
      • 22.3.1.5. String break-down
  • 22.4. Time profiler event log output
    • 22.4.1. Profile begin event
    • 22.4.2. Profile sample event
  • 22.5. Biographical profile sample event
  • 22.6. Non-moving GC event output
    • 22.6.1. Non-moving heap census
• 23. Care and feeding of your GHC User’s Guide
  • 23.1. Basics
    • 23.1.1. Headings
    • 23.1.2. Formatting code
      • 23.1.2.1. Haskell
      • 23.1.2.2. Other languages
    • 23.1.3. Links
      • 23.1.3.1. Within the User’s Guide
      • 23.1.3.2. To GHC resources
      • 23.1.3.3. To external resources
      • 23.1.3.4. To core library Haddock documentation
      • 23.1.3.5. Math
    • 23.1.4. Index entries
  • 23.2. Citations
  • 23.3. Admonitions
  • 23.4. Documenting command-line options and GHCi commands
    • 23.4.1. Command-line options
    • 23.4.2. GHCi commands
  • 23.5. Style Conventions
  • 23.6. ReST reference materials

Indices and tables

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