Commit d89b0471 authored by Sergei Trofimovich's avatar Sergei Trofimovich
Browse files

FastMutInt: fix Int and Ptr sizes when crosscompiling

Similar to
  https://ghc.haskell.org/trac/ghc/ticket/13491
  https://phabricator.haskell.org/D3122



SIZEOF_HSINT and SIZEOF_VOID_P are sizes of
target platform. These values are usually
not correct when stage1 is built.

It means the code

```haskell
  newFastMutInt = IO $ \s ->
   case newByteArray# size s of { (# s, arr #) ->
   (# s, FastMutInt arr #) }
   where !(I# size) = SIZEOF_HSINT
```
would try to allocate only 4 bytes on 64-bit-host
targeting 32-bit system.

It does not matter in practice as newByteArray#
implementation rounds up passed value to host's
word size. But one day it might not.

To prevent this class of problems in compiler/
directory 'MachDeps.h' contents is hidden when
ghc-stage1 (-DSTAGE=1) is built.
Signed-off-by: default avatarSergei Trofimovich <slyfox@gentoo.org>

Reviewers: austin, rwbarton, simonmar, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D3405
parent 03e34256
{-# LANGUAGE CPP, BangPatterns, MagicHash, UnboxedTuples #-}
{-# LANGUAGE BangPatterns, MagicHash, UnboxedTuples #-}
{-# OPTIONS_GHC -O #-}
-- We always optimise this, otherwise performance of a non-optimised
-- compiler is severely affected
......@@ -15,12 +15,7 @@ module FastMutInt(
readFastMutPtr, writeFastMutPtr
) where
#include "../includes/MachDeps.h"
#ifndef SIZEOF_HSINT
#define SIZEOF_HSINT INT_SIZE_IN_BYTES
#endif
import Data.Bits
import GHC.Base
import GHC.Ptr
......@@ -37,7 +32,7 @@ data FastMutInt = FastMutInt (MutableByteArray# RealWorld)
newFastMutInt = IO $ \s ->
case newByteArray# size s of { (# s, arr #) ->
(# s, FastMutInt arr #) }
where !(I# size) = SIZEOF_HSINT
where !(I# size) = finiteBitSize (0 :: Int)
readFastMutInt (FastMutInt arr) = IO $ \s ->
case readIntArray# arr 0# s of { (# s, i #) ->
......@@ -52,7 +47,8 @@ data FastMutPtr = FastMutPtr (MutableByteArray# RealWorld)
newFastMutPtr = IO $ \s ->
case newByteArray# size s of { (# s, arr #) ->
(# s, FastMutPtr arr #) }
where !(I# size) = SIZEOF_VOID_P
-- GHC assumes 'sizeof (Int) == sizeof (Ptr a)'
where !(I# size) = finiteBitSize (0 :: Int)
readFastMutPtr (FastMutPtr arr) = IO $ \s ->
case readAddrArray# arr 0# s of { (# s, i #) ->
......
......@@ -3,7 +3,7 @@
* (c) The University of Glasgow 2002
*
* Definitions that characterise machine specific properties of basic
* types (C & Haskell).
* types (C & Haskell) of a target platform.
*
* NB: Keep in sync with HsFFI.h and StgTypes.h.
* NB: THIS FILE IS INCLUDED IN HASKELL SOURCE!
......@@ -16,6 +16,31 @@
#ifndef MACHDEPS_H
#define MACHDEPS_H
/* Don't allow stage1 (cross-)compiler embed assumptions about target
* platform. When ghc-stage1 is being built by ghc-stage0 is should not
* refer to target defines. A few past examples:
* - https://ghc.haskell.org/trac/ghc/ticket/13491
* - https://phabricator.haskell.org/D3122
* - https://phabricator.haskell.org/D3405
*
* In those cases code change assumed target defines like SIZEOF_HSINT
* are applied to host platform, not target platform.
*
* So what should be used instead in STAGE=1?
*
* To get host's equivalent of SIZEOF_HSINT you can use Bits instances:
* Data.Bits.finiteBitSize (0 :: Int)
*
* To get target's values it is preferred to use runtime target
* configuration from 'targetPlatform :: DynFlags -> Platform'
* record. A few wrappers are already defined and used throughout GHC:
* wORD_SIZE :: DynFlags -> Int
* wORD_SIZE dflags = pc_WORD_SIZE (sPlatformConstants (settings dflags))
*
* Hence we hide these macros from -DSTAGE=1
*/
#if !defined(STAGE) || STAGE >= 2
/* Sizes of C types come from here... */
#include "ghcautoconf.h"
......@@ -96,4 +121,6 @@
#define TAG_MASK ((1 << TAG_BITS) - 1)
#endif /* !defined(STAGE) || STAGE >= 2 */
#endif /* MACHDEPS_H */
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