Changes between Version 1 and Version 2 of Commentary/Rts/Word


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Timestamp:
Sep 6, 2006 11:16:25 AM (9 years ago)
Author:
simonmar
Comment:

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  • Commentary/Rts/Word

    v1 v2  
    33= GHC Commentary: The Word = 
    44 
    5 The most important type in the runtime is {{{StgWord}}}, defined in [[GhcFile(includes/StgTypes.h)]] 
    6 [[HelloWorld(foo,bar)]] 
     5The most important type in the runtime is {{{StgWord}}}, defined in [[GhcFile(includes/StgTypes.h)]].  A word is defined to be the same size as a pointer on the current platform.  All these types are interconvertible without losing information, and have the same size (as reported by {{{sizeof}}}): 
    76 
     7 {{{StgWord}}}:: 
     8  An unsiged integral type of word size 
     9 
     10 {{{StgInt}}}:: 
     11  A signed integral type of word size 
     12 
     13 {{{StgPtr}}}:: 
     14  Pointer to {{{StgWord}}} 
     15 
     16The word is the basic unit of allocation in GHC: the heap and stack are both allocated in units of a word.  Throughout the runtime we often use sizes that are in units of words, so as to abstract away from the real word size of the underlying architecture. 
     17 
     18C-- only understands units of bytes, so we have various macros in [[GhcFile(includes/Cmm.h)]] to make manipulating things in units of words easier in {{{.cmm}}} files.