Fix zero-sized allocation crash on Windows#3085
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copybara-service[bot] merged 2 commits intogoogle-deepmind:mainfrom Feb 16, 2026
Merged
Fix zero-sized allocation crash on Windows#3085copybara-service[bot] merged 2 commits intogoogle-deepmind:mainfrom
copybara-service[bot] merged 2 commits intogoogle-deepmind:mainfrom
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On Windows, _aligned_malloc(0) returns NULL, which MuJoCo interprets as a fatal out-of-memory error. This causes crashes on models with empty arrays. Ensure a minimum allocation of 64 bytes for any 0-sized request. Fixes google-deepmind#2992
mmossg
approved these changes
Feb 11, 2026
JayFoxRox
reviewed
Feb 13, 2026
src/engine/engine_util_errmem.c
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| // pad size to multiple of 64 | ||
| if ((size%64)) { | ||
| size += 64 - (size%64); | ||
| if (size == 0) { |
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This feels a bit like fighting symptoms? Why do zero size allocations exist in the first place?
Maybe add a warning (or similar) here?
Another strategy might be to simply return NULL here to avoid the error + avoid allocation overhead.
There's also a corresponding check in mju_free which returns if a !ptr.
Contributor
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Hi @JayFoxRox, thanks for the feedback. Zero-size allocations occur when models contain empty arrays (e.g., no flex or mesh elements). Returning NULL for size 0 is indeed cleaner since mju_free already handles NULL pointers. I have updated the implementation to return NULL for zero-sized requests instead of padding to 64 bytes. |
mmossg
approved these changes
Feb 13, 2026
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This Pull Request fixes a crash on Windows when models contain empty arrays.
Changes
Fixes #2992