bpo-39943: Use calloc-based functions, not malloc+memset #19152
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Once I ran some microbenchmarks and it wasn't clear if calloc() was faster than malloc()+memset(0). It should, but I failed to measure such speedup. Well, the change is correct ;-) https://bugs.python.org/issue21233#msg217253 Sadly, pymalloc allocator has no efficient of calloc yet: it's just malloc+memset(0) in internally. But it should help for allocations larger than 512 bytes (not using pymalloc). |
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My concern wasn't speed, but in DRY and minimization of code. Still, a speedup would be nice if it happens. |
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If the compiler sees the I like |
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The |
For memory allocations larger than 512 bytes, libc malloc() is used and the libc is free to avoid memset if it knows that the memory is already initialized with zeros. I expect that memory allocated by mmap() doesn't provide uninitialized memory for example. This change should not make slower, but it's ok if it doesn't make Python faster neither. I expect that in some cases, it may be faster. But I don't bother enough to run exhaustive microbenchmarks ;-)
Sure, that's a cool enhancement since we had many security issues related to integer overflow in the past :-/ |
This consolidates a number of malloc+memset function calls to use their calloc-based equivalents.
https://bugs.python.org/issue39943