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Cleans up mergebackward implementation

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Uses consistent naming (_np) for native pointer equivalents of Lisp
    addresses
  Adds comments with a little explanation of what the code is doing
This commit is contained in:
Nick Briggs
2025-07-19 12:35:02 -07:00
parent 2c46a9473a
commit f375519dbc
1 changed files with 20 additions and 4 deletions
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24
src/gcfinal.c
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@@ -418,18 +418,34 @@ static LispPTR arrayblockmerger(LispPTR base, LispPTR nbase) {
/* */
/************************************************************************/
/*
* merges this block into the block behind it, unless there are
* disqualifying conditions:
* merging is turned off or
* this is the first block in array space or
* this is the first block in the 2nd array space or
* the block behind it is in use
* in which case it is linked onto the freelist (fwd and backward pointers)
* and added to the free block chain by size.
* If it can be merged,
*/
LispPTR mergebackward(LispPTR base) {
LispPTR pbase;
struct arrayblock *ptrailer;
struct arrayblock *ptrailer_np;
if (base == NIL)
return (NIL);
ptrailer = (struct arrayblock *)NativeAligned4FromLAddr(base - ARRAYBLOCKTRAILERWORDS);
/* back up to get the trailer of the previous block */
ptrailer_np = (struct arrayblock *)NativeAligned4FromLAddr(base - ARRAYBLOCKTRAILERWORDS);
/* check that there are no disqualifying conditions for merging with previous block */
if ((*ArrayMerging_word == NIL) ||
((base == *ArraySpace_word) || ((base == *ArraySpace2_word) || (ptrailer->inuse == T))))
((base == *ArraySpace_word) || ((base == *ArraySpace2_word) || (ptrailer_np->inuse == T))))
return (linkblock(base));
pbase = base - DLWORDSPER_CELL * ptrailer->arlen;
/* back up to the header of the previous block */
pbase = base - DLWORDSPER_CELL * ptrailer_np->arlen;
/* check that it is free, but skip free list checks */
checkarrayblock(pbase, T, NIL);
/* remove it from the free list */
deleteblock(pbase);
return (arrayblockmerger(pbase, base));
}