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changed behaviour of malloc(0) and optimized calloc #631

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changed behaviour of malloc(0) and optimized calloc #631

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@ZERICO2005 ZERICO2005 commented Sep 6, 2025 •
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__simple_malloc and __standard_malloc now return NULL when malloc(0) is called.

calloc (when __TICE__ is defined) now uses an inlined implementation of bzero which uses the $E40000 address to speed up the zero filling of memory.

Otherwise, it will use the previous memset implementation when __TICE__ is undefined.

runer112
runer112 reviewed Sep 6, 2025
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@ZERICO2005 ZERICO2005 changed the title optimized the zero filling in calloc (__TICE__ only) changed behaviour of malloc(0) and optimized zero filling in calloc Sep 6, 2025
@ZERICO2005 ZERICO2005 changed the title changed behaviour of malloc(0) and optimized zero filling in calloc changed behaviour of malloc(0) and optimized calloc Sep 6, 2025
@runer112 runer112 self-requested a review September 6, 2025 22:31
ZERICO2005
ZERICO2005 commented Sep 6, 2025
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src/libc/calloc.src Outdated
; inlined memset/bzero
; assumes that malloc(0) returns NULL, so we can skip the check for zero size
add hl, bc
cpd
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I assume it is okay for cpd to read nonnull_ptr_from_malloc + size

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ZERICO2005 commented Sep 16, 2025 •
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To reduce the complexity of this PR, I undid the allocator switches to nonzero_fill_calloc when malloc(0) is known to return NULL commits for now (which essentially added 4 different calloc variants). That way we can focus on the two important changes that will be made in this PR:

  • Changing the behavior of __simple_malloc(0) and __standard_malloc(0) to return NULL.
  • Optimizing calloc zero filling by using the $E40000 all zeros address

@ZERICO2005 ZERICO2005 marked this pull request as ready for review September 21, 2025 00:56
@runer112 runer112 self-assigned this Oct 16, 2025
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runer112 requested changes Oct 19, 2025
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@runer112 runer112 removed their assignment Oct 19, 2025
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runer112 approved these changes Oct 22, 2025
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If all checks pass, seems good.

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