Fix Immix working memory overflow with big blocks#1339
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Tutez64 wants to merge 1 commit intoHaxeFoundation:masterfrom
Open
Fix Immix working memory overflow with big blocks#1339Tutez64 wants to merge 1 commit intoHaxeFoundation:masterfrom
Tutez64 wants to merge 1 commit intoHaxeFoundation:masterfrom
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Use GetWorkingMemory() instead of recomputing the Immix block size through an int expression. With HXCPP_GC_BIG_BLOCKS, shifting the block count through an int overflows once regular heap usage reaches roughly 2 GiB, which can cause premature memory exhaustion or extremely long GC stalls. Also store GC memory tuning thresholds as size_t and parse their environment variables with strtoull so large values are not truncated.
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Summary
Fixes an overflow in Immix working memory accounting when
HXCPP_GC_BIG_BLOCKSis enabled.The problematic code computes the regular Immix heap size through an
int:With big blocks, this can overflow once regular heap usage grows past roughly 2 GiB. The fix uses
GetWorkingMemory(), which performs the shift throughsize_t.This also stores related GC memory tuning thresholds as
size_tand parses large environment variable values withstrtoull.Context
In a large OpenFL/hxcpp game, the regular heap consistently failed once it passed 2 GiB with:
After enabling
HXCPP_GC_BIG_BLOCKS,the game no longer crashed immediately, but it froze for a very long time instead, making it unplayable.With this fix, the same game can continue past that threshold. I was able to reach 12+ GiB of regular heap usage without hitting the previous stall/failure mode.
Repro
HxcppBigBlocksHeapOverflowRepro.zip
It retains many regular hxcpp objects until multi-GiB heap usage.
The repro is not a perfect match for the original game: without the fix, it usually stalls around 7-8 GiB rather than just past 2 GiB. However, it still demonstrates the same failure mode and shows that the fix lets the program continue to the configured target.