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| author | RyanGlScott <ryan.gl.scott@gmail.com> | 2015-12-19 11:09:52 +0100 |
|---|---|---|
| committer | Thomas Miedema <thomasmiedema@gmail.com> | 2015-12-19 11:09:59 +0100 |
| commit | 2cc5b607df27e702541985f7c4c987806c4ec2a1 (patch) | |
| tree | 2ab126c6dccef992bf689a336a3aed6590a7d052 /docs/users_guide | |
| parent | b2670fc47754288224b825a3308b92642ccf7e73 (diff) | |
| download | haskell-2cc5b607df27e702541985f7c4c987806c4ec2a1.tar.gz | |
Documentation, tests for hsc2hs's new #alignment macro
Adds two tests (one for Trac #4340 and one for Trac #10272), as well as
advice on how to fix your code if `hsc2hs` emits warnings with GHC 8.0
due to a redefinition of `#alignment`. (I also put the advice in the
[GHC 8.0 Migration
Guide](https://ghc.haskell.org/trac/ghc/wiki/Migration/8.0).)
Reviewed By: thomie
Differential Revision: https://phabricator.haskell.org/D1663
GHC Trac Issues: #4340, #10272
Diffstat (limited to 'docs/users_guide')
| -rw-r--r-- | docs/users_guide/7.12.1-notes.rst | 26 | ||||
| -rw-r--r-- | docs/users_guide/utils.rst | 4 |
2 files changed, 30 insertions, 0 deletions
diff --git a/docs/users_guide/7.12.1-notes.rst b/docs/users_guide/7.12.1-notes.rst index 749f7afbc1..d443a0a65e 100644 --- a/docs/users_guide/7.12.1-notes.rst +++ b/docs/users_guide/7.12.1-notes.rst @@ -321,6 +321,32 @@ Package system - TODO FIXME. +hsc2hs +~~~~~~ + +- ``hsc2hs`` now supports the ``#alignment`` macro, which can be used to + calculate the alignment of a struct in bytes. Previously, ``#alignment`` + had to be implemented manually via a ``#let`` directive, e.g., :: + + #let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__) + + As a result, if you have the above directive in your code, it will now emit + a warning when compiled with GHC 8.0. :: + + Module.hsc:24:0: warning: "hsc_alignment" redefined [enabled by default] + In file included from dist/build/Module_hsc_make.c:1:0: + /path/to/ghc/lib/template-hsc.h:88:0: note: this is the location of the previous definition + #define hsc_alignment(t...) \ + ^ + + To make your code free of warnings on GHC 8.0 and still support earlier + versions, surround the directive with a pragma checking for the right GHC + version. :: + + #if __GLASGOW_HASKELL__ < 800 + #let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__) + #endif + Libraries --------- diff --git a/docs/users_guide/utils.rst b/docs/users_guide/utils.rst index 9c1237dd02..f490bfa2d8 100644 --- a/docs/users_guide/utils.rst +++ b/docs/users_guide/utils.rst @@ -224,6 +224,10 @@ Meanings of specific keywords: Computes the size, in bytes, of ``struct_type``. It will have type ``Int``. +``#alignment ⟨struct_type⟩`` + Computes the alignment, in bytes, of ``struct_type``. It will have type + ``Int``. + ``#enum ⟨type⟩, ⟨constructor⟩, ⟨value⟩, ⟨value⟩, ...`` A shortcut for multiple definitions which use ``#const``. Each ``value`` is a name of a C integer constant, e.g. enumeration value. |