4. Release notes for version 8.4.2 — Glasgow Haskell Compiler 8.4.4 User's Guide

# Glasgow Haskell Compiler User's Guide

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# 4. Release notes for version 8.4.2

## 4.1. Highlights

This is a bug-fix release resolving several regressions introduced in 8.4.1.

The highlights, since the 8.4.1 release, are:

- Fixed a regression causing uses of `Control.Exception.evaluate` to be incorrectly optimised, resulting in incorrect evaluation behavior (Trac #13930)
- Fix a regression causing the interpreter to segmentation fault when built with profiling (Trac #14705)
- DWARF debug information support has been significantly improved (Trac #14894, Trac #14779)
- A regression in runtime performance of code involving `newtype`s has been fixed (Trac #14936)

## 4.2. Full details

In addition to the highlights listed above, this release resolves a number of other issues, described below.

### 4.2.1. Compiler

- A bug affecting GHC’s debug output support (`-g`) which resulted in invalid code being generated for string literals (Trac #13868)
- Trac #14918, where `Read` instances for types with field names containing `#` would fail to parse, has been fixed.
- Several compiler panics have been resolved (Trac #12158, Trac #15002, Trac #14933, Trac #14959)
- Fix a regression in which derived `Read` instances for record data types with field names ending with `#` (by way of `-XMagicHash`) would no longer parse valid output.

### 4.2.2. Runtime system

- A bug causing panics while running programs with retainer profiling (`-hr`) was fixed (Trac #14947)

### 4.2.3. Template Haskell

No changes.

### 4.2.4. `ghc` library

No changes.

### 4.2.5. `base` library

- Version bumped to 4.11.1.0 to account for the addition of `GHC.IO.FixIOException`
- Add the `readFieldHash` function to `GHC.Read` which behaves like `readField`, but for a field that ends with a `#` symbol.

### 4.2.6. `integer-gmp` library

- Version bumped to 1.0.2.0 to account for the addition of `powModSecInteger`.
- Define `powModSecInteger`, a “secure” version of `powModInteger` using the `mpz_powm_sec` function.

### 4.2.7. Build system

- `configure` now takes a `--disable-dtrace` flag, allowing workaround of Trac #15040.
- A bug breaking GHC builds bootstrapped on Darwin has been fixed (Trac #14972)

## 4.3. Included libraries

The package database provided with this distribution also contains a number of packages other than GHC itself. See the changelogs provided with these packages for further change information.

Package | Version | Reason for inclusion
--- | --- | ---
ghc | 8.4.4 | The compiler itself
Cabal | 2.2.0.1 | Dependency of `ghc-pkg` utility
Win32 | 2.6.1.0 | Dependency of `ghc` library
array | 0.5.2.0 | Dependency of `ghc` library
base | 4.11.1.0 | Core library
binary | 0.8.5.1 | Dependency of `ghc` library
bytestring | 0.10.8.2 | Deppendency of `ghc` library
containers | 0.5.11.0 | Dependency of `ghc` library
deepseq | 1.4.3.0 | Dependency of `ghc` library
directory | 1.3.1.5 | Dependency of `ghc` library
filepath | 1.4.2 | Dependency of `ghc` library
ghc-boot | 8.4.4 | Internal compiler library
ghc-compact | 0.1.0.0 | Core library
ghc-prim | 0.5.2.0 | Core library
ghci | 8.4.4 | The REPL interface
haskeline | 0.7.4.2 | Dependency of `ghci` executable
hpc | 0.6.0.3 | Dependency of `hpc` executable
integer-gmp | 1.0.2.0 | Core library
mtl | 2.2.2 | Dependency of `Cabal` library
parsec | 3.1.13.0 | Dependency of `Cabal` library
process | 1.6.3.0 | Dependency of `ghc` library
template-haskell | 2.13.0.0 | Core library
text | 1.2.3.1 | Dependency of `Cabal` library
time | 1.8.0.2 | Dependency of `ghc` library
transformers | 0.5.5.0 | Dependency of `ghc` library
unix | 2.7.2.2 | Dependency of `ghc` library
xhtml | 3000.2.2.1 | Dependency of `haddock` executable

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